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Motor Oil 104

Discussion in 'Technical Q&A' started by AEHaas, Nov 15, 2004.

  1. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    First read:
    http://ferrarichat.com/forum/showthread.php?p=134538546&posted=1#post134538546


    Motor Oil 104
    Part Four. It is not what we thought.

    Now let us finish talking about the differences of mineral verses synthetic oils. I will compare the same weigh or grade of oils showing that the operating viscosities are the same whereas the startup viscosities vary:

    Mineral oil:

    Oil type...Thickness at 75 F... at 212 F...at 302 F

    Straight 30..........250....................10..........3
    10W-30..............100.....................10..........3
    0W-30..........There are none in this range......



    Synthetic oil:

    Oil type...Thickness at 75 F... at 212 F...at 302 F

    Straight 30...........100...................10...........3
    10W-30................75...................10...........3
    0W-30.................40...................10...........3

    Since the synthetic oil thickens less on shutdown your startup will be easier and so will the stress on your engine. This is perhaps the best thing the synthetic class has over the mineral based oils.

    People sometimes use a thicker oil to minimize gasket leaks. This seems obvious to me. Repair the gasket. Do not destroy your engine with an oil that is too thick for proper function.

    Some people have said they use thicker oils because they only use their cars every 2, 3 or 4 weeks. They are afraid that thin oils will fall off the engine parts and result in a lack of lubrication at startup. Think about your lawn mower over the winter. I gets gummed up solid. The oil and fuel thicken over time resulting in engine failure. Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates. Thick, old, waxy oil can only be bad.

    I have seen several car owner manuals that are now stating that oils do not need to be changed but every 7,500 miles or more. The same manual also states OR every 12 months, whichever occurs first. My feeling is that you can probably go 5,000 miles on the average (in a sports car) but you must change your oil in the spring time at a minimum, particularly up north. Oils form waxes in icy cold weather. There is a permanent thickening of the oil.

    Some automotive manufacturers are backing down on oil change intervals to 5,000 miles or less and some advocate changing the oil at least every 6 months as well. I think this is because of the tendency for oils to thicken in very hot engines (not ambient conditions, just hot engines). Also because of thickening from the cold of winter and from sludge build up that cannot be filtered out.

    I truly believe that oil is much better being too thin than too thick. Over the years we have been going to thinner and thinner oils despite hotter engines with turbos and the like. The tendency is that people figure they need a 40 weight oils but then use a 50 instead. Better thinking is that if you think you need a 40, use a 30 weight oil instead. I firmly believe this based on all I know about oils.

    As it turns out synthetic oils do cling to parts better as they have higher film strength than mineral oils. Synthetics are thinner overall. They have greater slipperiness. Yet they stick better to engine parts. Again, this concept is the opposite of normal thinking.

    The thickness of moving oil is measured in centiStokes or cS. Most engines want the oil viscosity to be around 10 cS at normal operating temperature. The really thick multigrade oils have a viscosity of 20 cS at operating temperature. One is not twice as thick as the other, it is only 10 cS thicker.

    As we increase the heat from 212 F to 302 F the most commonly recommended oil thins from 10 cS to 3 cS. The thicker oil drops from 20 cS to 4 cS. Note that in a very hot engine the difference between the two oils is now only 1 - 2 cS. In other words they have about the same thickness. There is little advantage to a thicker based oil as a 20W-50 at very high temperatures. No, the 4 cS oil is not twice as thick as the 2 or 3 cS oil. This difference is almost insignificant.

    There is a huge advantage of using the thinner, 10W-30 at startup where 90 percent of the engine wear occurs. At 75 F the thicker oil has a viscosity in the range of 250 cS while the thinner oil has a viscosity of 100 cS. The thicker stuff is 150 cS thicker. This is a very big difference. I am using the 20W-50 as my thicker oil example here.

    People are always asking about adding things as Slick 50 into the oil tank. Do not do this. The oil companies and engine manufacturers work together very hard to give you the product you need. Engines are running hotter, longer with more BHP from less CID. Smaller, more efficient engines are getting us more MPG and yet better acceleration. These engines last longer and are more reliable.

    Part of that reason is the nature of the lubricants. There is a lot of competition to get us the best working motor oil. Independent additives cannot make the oil better and in many cases makes things worse. There have been engine failures as a result of adding some of these aftermarket additives to motor oil.

    Motor oil that is labeled for RACING ONLY is not usable for every day driving. Often these have more additives that are toxic to your catalytic converters and the environment. These oils generally do not have detergents. These are very important for your engine unless you plan on taking it apart every few weeks and cleaning every single surface. The oils do not meet the API / SAE requirements for ratings as SJ, SL or now SM.

    You do not need to use the exact oil type and brand that your car manual tells you to use. Oils are pretty general. They are not that different. Ferrari is married to Shell. If you call them up and ask to use Valvoline instead they will tell you that they have not tested that brand in their cars. They only tested the engine with Shell oils. They cannot comment on the performance of other oils in their engines. This is a fair statement. The reality is that the Shell and Valvoline oils of the same specification (viscosity, API and SAE ratings, synthetic or not) are very similar. ( I do have my bullet proof vest on ).

    People often say that their old 1980 car manual says to use a specific Brand-X motor oil. They keep trying to locate these older oils. First, just about any oil brand that meets the original specifications will do. Second, all oils are much, much better now. They are all much better. One could say that synthetic oils are better than mineral oils but is is hard to say that one brand is that much better than any other. Personally, I do stick to the big names. It does not mean that small motor oil companies are not as good. They could be better for all I know.

    Using an oil that is less thick at startup has other benefits. Let us compare a synthetic 10W-30 to a mineral based 10W-30. Both give you a viscosity of 10 cS at normal engine operating temperatures. They both thin to 3 cS at high temperatures. At 75 F tomorrow morning the story will be different. The startup viscosity of the synthetic will be 50 whereas the mineral based 10W-30 will be 75. Again, both are too thick at startup but the synthetic will cause less startup time period wear and tear. You will get a little better gas mileage too.

    The synthetic lubricated engine will turn over easier. This has the effect of using less power from your starter motor. It will last longer. Your battery has less of a current draw. This will also last longer. The battery was discharged less during the start so the alternator will rob less power from your engine to recharge. The alternator lasts longer and you get a little better gas economy. The only downside of synthetic lubricants is the cost. They cost 2 or 3 times as much as mineral based oils. Never-the-less I use plain Pennzoil multigrade mineral based 5W-20 in my Ford Expedition. This oil is thin enough at startup to have many of the attributes I just mentioned.

    aehaas
    For those who want all chapters now:
     
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  3. bearduke1

    bearduke1 Rookie

    Oct 19, 2004
    26
    South Carolina
    Full Name:
    Bubba Joe
    "Some people have said they use thicker oils because they only use their cars every 2, 3 or 4 weeks. They are afraid that thin oils will fall off the engine parts and result in a lack of lubrication at startup. Think about your lawn mower over the winter. I gets gummed up solid. The oil and fuel thicken over time resulting in engine failure. Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates. Thick, old, waxy oil can only be bad."

    My primary reason for a using a thicker & waxy oil is the staying power of the oil on internal engine parts prone to rusting (improved surface tension on cams and lobes), especially on engines which aren't run frequently. I'd say frequently is every few days. Although there may be newer additive packages in synthetics which prevent corrosion, the tried and true procedure of using thicker oil seems to work OK, and in this case wax formation is a plus--not unlike having a preservative oil in the engine.

    Sure the engine takes longer to warm up before driving and you have to be more careful of excessive pressure early on, but once the engine warms up I think it's OK. Anyhow, that's one of my (and others' thoughts).
     
  4. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    I just added this to chapter 5:
    In ASTM D 4485 3.1.4: “Terminology: Engine oil- a liquid that reduces friction and wear between moving parts within an engine, and also serves as a coolant.”
    aehaas
     
  5. GoodWood

    GoodWood Formula Junior

    Oct 2, 2004
    351
    SE Florida/Indiana
    Full Name:
    Steve
    Thank you for taking the time to explain these technical things in a way a lay person can still understand. You've got me sold on the thinnest possible oil (within the manufacturer's recommendation) for my incoming (any day now) CS, as well as the necessity of changing it frequently. My question is; since the majority of engine wear occurs at startup, do you recommend not revving the engine at all during the first minute or so, or just driving off normally? What about when it's near, or even below freezing outside, and the garage is just as cold?
     
  6. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    I start the engine and go. However, I never step on it until I get up to full operating temperature. When you are just driving to work you are only using maybe 20 - 30 BHP from your engine. The stress is minimal to the parts. Just keep the RPM down and there will be minimal wear and tear.

    I have actually noticed that my engine runs a few degrees hotter in the cooler months. When I drive to work the 15-20 minute drive may warm up the engine but the grease in the wheel bearings and transmission and axle warm up slower. There is no internal heat source as in the engine. There is simply more drag.

    I measured the transaxle temperature in mid summer on my Maranello after driving home from work. It was only 123 F. Obviously the oil is still think. I wonder what it will be in the winter. I will try to remember to take its temperature. After all, I am a doctor.

    aehaas
     
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  8. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    Thanks for the articles. I enjoy reading them.
    Now for 308s the recommended oil is 20W-50. I have spoken with over 20 F-cars techs. and all say to stay with 20W-50 in all 308 models. From reading your posts it is way too thick for cold starting. So why are all of the techs. recommending it if 20W-50 isn't adequate? Would you say 5-30 is better?
     
  9. ants2au

    ants2au Formula Junior

    Nov 19, 2003
    690
    Sydney Australia
    Full Name:
    Anthony
    My 308 GT4 has a plaque that says 10W40
    a 308 engine is a 308 engine.




     
  10. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    Your manual is correct. When it was written that was all that you could pick from. If they rewrote the manual to take advantage of current advancements they would recommend a 5W-50. They may even recommend a 0W-40. Remember, that manual is 25-30 years old. They were not able to make predictions of what motor oil can do today.

    A 5W-50 has the same operating properties as that older 20W-50 but is less honey-like at startup and therefore has less startup period wear and tear. Also, they did not have synthetic oils. Now we have them and they are completely different than the mineral oils of the past. Finally, the current oils are far superior in every single testable aspect in every way.

    aehaas
     
  11. Nuvolari

    Nuvolari F1 Veteran
    Sponsor Owner

    Sep 3, 2002
    5,587
    Toronto / SoCal
    Full Name:
    Rob C.
    First allow me to offer my sincere thanks for the continuing education.

    All this year in my 308 I have run 0W-40 Mobil 1 having changed from 20W-50 Mineral oil. Without a doubt the car cranks over easier, revs more freely and generally drives better. I have had NO side effects. Oil pressure is the same, there are no leaks, and there is no increased consumption. I highly recommend it to any owner.
     
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  13. Dom

    Dom F1 Veteran
    Rossa Subscribed Owner

    Nov 5, 2002
    7,942
    Southern California
    Full Name:
    Dom V.

    Interesting. My 1975 308 GT4 says 10w50 in the manual. I had been using Castrol 20w50 (dino oil), but at the last oil change switched to Mobil 1 15w50. It sounds like Ali is suggesting 5w50 might be better. Does Mobil 1 make a 5w50? Is there a suitable alternative?

    Ali, thanks for your guide. It is spectacular. I will print it out later and read up on it.

    Dom
     
  14. 4i2fly

    4i2fly Formula 3

    Apr 16, 2004
    1,330
    SF, Bay Area
    Dr. Haas,

    How do engine mfgs. choose motor oil for a given engine, when they already anticipate such diverse operating conditions? Do they choose something in the middle of the spec? Are owners then left to choose the best oil for their own operating environment?

    Thanks,
    Matt
     
  15. ants2au

    ants2au Formula Junior

    Nov 19, 2003
    690
    Sydney Australia
    Full Name:
    Anthony
    It is interesting. Mine's a '78

     
  16. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    From Chapter 6:

    50 wt:
    Castrol Syntec 5W-50
    Penn Synthetic 5W-50



    D 4485 defines 2 types of engines. 1-light duty-those engines generally used under less than peak output conditions. And 2-heavy duty-those engines generally used continuously at or close to peak output conditions.
    Boats and airplanes, as well as a lot of industrial engines operate at heavy duty conditions. I classify hot race track conditions as heavy duty.

    I equate this to using your car on the track in hot racing conditions verses all other types of driving. For these 2 situations you generally need two different oils.

    In the past Ferrari seems to have recommended only a racing oil. Newer manuals differentiate the difference and recommend different oils for these 2 conditions. My 575 Maranello manual recommends 0W-40, 5W-40 and 10W-60 racing oil but only "for hot track racing conditions." Note how specific they are. Use the thick stuff only when racing and only for "hot" track conditionds.

    aehaas
     
  17. Ricambi America

    Ricambi America F1 World Champ
    Sponsor Owner


    I think I missed something. Didn't Dr. Haas say that changing synthetic oils every 3000 miles (or whatever) is unnecessary? It's not about dirty oil, it's based on the dissapation of detergents and other additives.

    Ali - If the longevity of synthetic oil is so superior here's a theory I'd like you to comment on: Assume my car burns 1 quart of synthetic every 1,000 miles and it holds 12 quarts. I drive exactly 1000 miles per month. If I "top off" with a quart every month, have I basically done a full oil change at the end of the year? What if I simply replace my oil filter on December 31st, and keep on driving?

    Am I all wet on this one?

    -Daniel
     
  18. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    If you started with an oil having no additives at all then added a can of oil with the full concentration each month, you would slowly increase the overall concentration of additives. If you started with oil having all the additives and added a can of the same stuff every month, the concentration would slowly go down. Somewhere between these 2 points would be an equilibrium. The final concentration would depend on the rate of additive consumption. A slow rate of use would result in a higher equilibrium concentration and probably be OK. But again, there are other concerns as products of oxidation and solids not filtered would accumulate. You would still have to change the oil at some point but may be able to extend the time periods. I assume you are using a full synthetic.

    What exact oil are you using? One with less evaporation, maybe of a higher flash point may last longer and require less adding of oil. For example, if you are using Shell Helix Ultra 5W-40 and change to a very similar product, Mobil One 0W-40 you get 30 C higher flash point and maybe far less oil consumption.

    In general, Amsoil, Mobil 1, Red Line and Valvoline fully synthetic oils have the higher flash points.
    Shell Helix Ultra has the lowest flash points. Maybe they want it this way. One- it evaporates more and you have to buy more, good for them.
    Another- it evaporates more so you keep adding in new oil with a little more additive, good for you !
    Who knows?

    aehaas
     
  19. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    When I took delivery of my 575 Maranello I checked the oil. When I changed the oil for the first time at 775 miles it was one quart down. The car was delivered with 5W-30 Shell Helix Ultra. I changed to 0W-30 Mobil 1. By the second oil change at 2,250 miles there was no oil consumption. At that time I changed to 0W-20 Mobil 1. I now have 5,300 miles and there has been no oil consumption, none. I feel as though I want to change the oil again but it is just so clean. I will probably wait until springtime and change it then.

    aehaas
     
  20. f355spider

    f355spider F1 World Champ
    Rossa Subscribed Owner

    May 29, 2001
    17,178
    USA
    Full Name:
    Hugh G. Rection
    I don't think the Pennzoil 5w-50 is available any longer...I can no longer find it in the Northwest...
     
  21. lromanosky

    lromanosky Rookie
    BANNED

    Aug 27, 2004
    38
    calgary, canada
    Full Name:
    lawrence romanosky
    I've been trying to figure out the best oil for my 328 for the several months that I've owned it. I've read all the posts, checked the manual, changed oil with different weights a couple of times, monitered pressure and temperatures, fussed over correct levels etc.

    Now, with a sense of relief, I can settle with a decision with some confidence. It will be Mobil One 0w40. I tried 15/50 and the pressure was a bit high according to the manual, and I've tried 5/30 and it was a bit low-though both in the ballpark.

    Many thanks to Dr. Haas for his time and expertise.

    BTW, while the manual says 10L capacity, only 8L drains out. I run my oil level at slightly above MAX stone cold, and the if I check the oil, warm, immediately after I cut the engine, the level is slightly above th MIN mark.

    Cheers, Lawrence.
     
  22. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
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    Ali E. Haas
    Just to show some of the parameters that are tested in automotive gasoline engine oils I was able to get permission to reproduce the following from ASTM D 4485-03a. Most people do not get to see this data as the documents cost money and are of course copyrighted. With permission however:

    From Table 2, S Engine Oil Categories
    API SL CATEGORY (my note - most areas that give a measurement in mm = micrometers. It was difficult to transform the data into web friendly stuff.)

    Engine Test Method.....Rated or Measured Parameter.....Primary Performance Criteria
    Sequence IIIF.....Kinematic viscosity, % increase at 40°C, max.....275
    ...............Average piston skirt varnish rating, min....................9.0
    ...............Weighted piston deposit rating, min.........................4.0
    ...............Screened average cam-plus-lifter wear, mm, max.....20
    ...............Hot Stuck Rings....................none
    ...............Low temperature viscosity performance ..........report
    Sequence IVA.....Cam wear average, mm, max........120
    D 5302 B..........Cam wear average, mm, max...........127
    (Sequence VE AD).....Cam wear max, mm, max ......380
    D 6593
    (Sequence VG) .....Average engine sludge rating, min.....7.8
    ...............Rocker arm cover sludge rating, min...............8.0
    ...............Average piston skirt varnish rating, min..........7.5
    ...............Average engine varnish rating, min.................8.9
    ...............Oil screen clogging, %, max...............20
    ...............Hot stuck Compression rings..........none
    ...............Cold stuck rings......................report
    ...............Oil screen debris, %...............report
    ...............Oil ring clogging, %.................report
    D 6709 Bearing weight loss, mg, max..........26.4
    (Sequence VIII) Shear stability..........footnote


    Bench Test and Measured Parameter....................Performance Criteria

    Test Method D 6557 (Ball Rust Test), average gray value, min.....100
    Test Method D 5800 volatility loss, % max...................................15
    Test Method D 6417 volatility loss at 371°C (700°F), % max.....10
    D 6795 (EOFT), % flow reduction, max...............50
    D 6794 (EOWTT), % flow reduction, max
    ..........With 0.6 % H2O..........50
    ..........With 1.0 % H2O..........50
    ..........With 2.0 % H2O..........50
    ..........With 3.0 % H2O..........50
    Test Method D 4951 or D 5185, phosphorus % mass, max.....0.10
    Test Method D 892 foaming tendency (Option A)
    Sequence I, max, foaming/settling........10/0
    Sequence II, max, foaming/settling........50/0
    Sequence III, max, foaming/settling......10/0
    Test Method D 6082 (optional blending required) static foam max, tendency/stability.....100/0
    Test Method D 6922 homogeneity and miscibility..........footnote
    High temperature deposits (TEOST MHT-4), deposit wt, mg, max.....45
    Test Method D 5133 (Gelation Index), max ...............12

    “Extracted, from ASTM D 4485-03 Standard Specification for Performance of Engine Oils, copyright ASTM International, 100 Barr Harbor Drive, Wets Conshohocken, PA 19428, USA.”

    I was going to show more but it is a pain to make it work right. Anyway you can get an idea of how many things are tested. A lot of work goes into motor oils to make sure we get the best engine performance.

    aehaas
     
  23. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    I went over to Pennzoil synthetic oils. They no longer list the 5W-50 oil but they do have a data sheet on it. They now have a 5W-40 instead but there is no data sheet on this oil.

    I am not sure but the demand for heavy weight oils is probably less than in the past.

    aehaas
     
  24. 308GTS

    308GTS Formula 3

    Dec 27, 2001
    2,220
    TN
    I disagree. My QVs have Nikasil liners your GT4 doesn't. Also 4 valves per cylinder. So no a 308 engine isn't a 308 engine.
    My 78 308 says 20W-50 also. All of my US spec owners manuals say 20W-0 also.
    Are you sure yours isn't a 208?
     
  25. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    I find this very interesting:

    "Pennzoil® 10-Year/250,000 Mile Limited Warranty
    Either when you purchase a Pennzoil® oil change or change your own oil with Pennzoil®, We will give you a FREE lubrication limited warranty that will protect all your engine's lubrication-related parts, such as the pistons, timing chain, valve stems and cam shafts, for 10 years or 250,000 miles.

    How to get coverage.
    To qualify for coverage all you have to do is get a Pennzoil® oil change or change your oil with Pennzoil®. Your engine must have less than 36,000 miles and have been manufactured within the last 48 months. It's that easy!

    How to keep it.
    Just get a Pennzoil® oil change at a service center or change your oil with Pennzoil® every 4,000 miles or 4 months, whichever comes first. This may not be the same as some vehicle manufacturers recommend, but neither is the length of our limited warranty. The oil filter and air cleaner elements must be replaced and the emission control system must be maintained in accordance with the vehicle manufacturer's recommendations. You have to take very good care of your engine if you want it to last for ten years. Or 250,000 miles. Our limited warranty is transferable. The Pennzoil® limited warranty offers something that could prove valuable if you sell your vehicle before it's gone 250,000 miles. The limited warranty can be transferred to the next owner.

    How to Enroll.
    Simply fill out and submit our on-line application. The Pennzoil® limited warranty is only available in the United States and Canada. For full details on this Limited Warranty Program, call 1-877-422-7645 and switch to Pennzoil® oils and greases to take better care of your engine!"




    What I find odd is that they do not specify a synthetic. You can use their regular multigrade oil. Also, you can go 4,000 miles but the catcher is that you can only go 4 months between oils changes. Very interesting.

    And "The limited warranty can be transferred to the next owner."

    aehaas
     
  26. 4i2fly

    4i2fly Formula 3

    Apr 16, 2004
    1,330
    SF, Bay Area
    I was watching speedtv last night and i think it was autoweek speedtv edition. They were test driving the new 997 and mentioned the oil change interval has been increased to two years/20k miles. And they still recommend the same 0W40 mobil 1 oil for the car. The oil hasn't changed or has it, or maybe the data they have collected from previous generation has led them to extend this interval, or could it be due to re-design of the engine for lubrication? Any comment Dr. Haas?
     
  27. AEHaas

    AEHaas Formula 3

    May 9, 2003
    1,361
    Osprey, Florida
    Full Name:
    Ali E. Haas
    The SL rated oil has only been out since 2001. We have only been able to test it in cars for 3 years. The oil is a significant improvement from the previous SJ rating.

    Also, I seem to remember that Mobil put out a note that stated their Mobil 1 formulation has changed somewhat this summer. It may be that they already meet the SM rating with the new additives. This is my guess.

    I think the SL is that good, and the synthetics have been good to start. They are improving fast. Again, I am excited about the upcoming SM and was very happy with the changes I saw in SL over SJ.

    My bias is that the newer, thinner oils are actually providing better protection than thicker, older oils, contrary to popular belief. Easier startup means smaller starters and smaller batteries as somebody else already mentioned. You change the oil less and the engine lasts longer. How good is that?

    aehaas
     
  28. jselevan

    jselevan Formula 3

    Nov 2, 2003
    1,858
    Dr Haas - I read (with interest) your dissertation on oil. As I sit back and digest your thoughts, however, it seems that much of the information presented speaks to the delivery of oil to working surfaces, and not to the comparative change in coefficient of friction that different oils produce. After all, it comes down to the coefficient of friction between surfaces, does it not?

    Your statement: "Anyway, oil on the surface of parts does not lubricate. It is the FLOW of oil between parts that lubricates," would be accurate if the moving parts were suspended in a bearing, with oil representing the suspension fluid. In that scenario, a suspended part requires a certain volume of flow to remain suspended. Piston rings, cam lobes on shims, rod-end journals, etc., are metal-to-metal contact and not suspended.

    Thus, a molecular layer of oil must sit between the metal surfaces and reduce the coefficient of friction. Your discussion speaks mainly to the inverse relationship between flow and pressure, between temperature and viscosity. Furthermore, you do not address the concept of a "constant flow" pump. The electrical analog is a constant current source. If the oil pump can deliver a specified cubic measure per minute within a wide range of pressure head, as I suspect mechanical pumps do, then flow through oil channels occurs independent of, and irrespective of the pressure measured by your oil pressure gauge.

    Finally, I come back to the question of cold start. As previously stated, my experience is that oil stays on metal surfaces for months, if not years. The noise that you observed when starting your engine following an oil change may be simply the meshing gears of the oil pump sucking air as they prime the pump.

    Your thoughts are appreciated.

    Jim S.
     

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