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LOW weight (5w-30) vs. HIGH weight (15w-40+) oils...

Discussion in 'Technical Q&A' started by rob lay, Feb 20, 2004.

  1. rob lay

    rob lay Administrator
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    I know, discussed many times in our oil threads, but I thought this topic would merit it's own thread.

    I bought a new 1999 Challenge Series manual (Thanks Sodacoms!) and they required the race cars use Shell Helix 5w-30 back then.

    I've been a strong believer in light weight oils for a couple years now. I think the light weight oils allow less friction, so lower temps and more HP.

    Possible negatives might only be an engine is built for a certain weight oil for tolerances and you should stick with it.

    Any concern that in track conditions, a 5w-30 oil might not protect your engine when really stressed? Ferrari didn't seem to think so.

    I change my Challenge oil every other track day and 328 oil every 3 months or 1,250 miles.

    Thanks,
    rob
     
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  3. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,183
    Rob; I can relate my experience so far.

    I did a year of 20W50 track events, and I have done 1/2 a year of 10W40 track events, sometime this summer I am going to test a 10W30 or a 0W30 oil at TWS. I even did a few events with 50% 20W50 and 50% 10W30 oil trying for a 10W40 mixture.

    In summertime heat (95+ dF) after at least 20 minutes of hard track driving I would be seeing 280 dF oil temps on 20W50 oil and only 265 dF temps on the 10W40 stuff. The 50/50 mixture oil had the same high temps as the 20W50 oil. After a cool down lap, with both oils in the 220 dF range, the 10W40 oil had higher idle pressure than the 20W50 stuff. The 50/50 oil had the oil pressure of the 20W50 stuff.

    The car starts faster on the 10W40 stuff. The only drawback I have seen is the oil consumption went from basically zero with 20W50 to about 1qt in 1,500 miles with 10W40 oil.
     
  4. AEHaas

    AEHaas Formula 3

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    Mitch,
    The 10-40 may have a lower vapor pressure. It is somewhat viscosity independent. I still want to know what the 0-30 does for you.

    Rob,
    Engine wear occurs almost exclusively at start up, not at operating temperatures. The viscosity needed is whatever the manufacturer calls for. In my Maranello the manual states to shoot for 70 - 80 PSI at 6,000 RPM. On the track at higher engine load a thicker oil will be required over lesser load conditions.

    I am currently getting 70 PSI at 2,000 RPM with around town driving. I will try 10W oil next. Currently I am using Mobil 1 0W-20. Ferrari NA knows this and wants me to keep them informed.

    Again, in all cases use 0W-X as you want the startup thickness of the oil to be least honey-like as possible.

    aehaas

    Edit- At start up, Mobil 1 0W-30 is not as honey-like as their 10W-30. At 212F their 0W-30 is actually a little more viscous than the 10W-30. The numbers on the can do not always tell you exactly what is going on inside.
     
  5. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,183
    The experiment has been queued up, just waiting for the hot part of the year to run it.

    Is vapor pressure linked to flash point?
     
  6. rob lay

    rob lay Administrator
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    Maybe a dumb question, but I don't know for sure.

    Will a lower vicosity oil have a lower pressure?
     
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  8. Aeroengineman

    Aeroengineman Formula Junior
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    Yes because it squirts through the oil passages easier. The restriction that the oil passages have raises the oil pressure.
     
  9. DeWitt

    DeWitt Rookie

    Jan 29, 2004
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    A flash point is the lowest temp in which a fuel can form a ignitable vapor in air. The flash point of a liquid is related to the rate in which it vaporizes, which does depend on the liquids vapor pressure. Vaporization rises with an increase in temperature. For very volatile liquids like acetone or methyl-ethyl-ketone, which in a closed system do exert a high vapor pressure, have flash points that are ignitable below room temp (~25C).

    A good baseline minimum flash point a motor oil should have is roughly 400F. A lower flash point can lead to oil consumption because the heat produced from the cylinder walls can basically burn off an oil with a low flash point.

    /got nothing. Hope this helps you out.
     
  10. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    7,183
    Rob: most of the time oil pressure is regulated by the blow off valve, which is set around 100 PSI for the F355 engine and controlled by a spring.

    When I switched from 20W50 to 10W40 I lost around 5 PSI from 105 to 100 PSI at normal 65 MPH cruise speed anywhere above 2,200 RPMs with warm idle droping from 80 to 75 PSI. Cold start idle pressure in still in the 85 PSI range. I used to have a plot of the various oils and plotted them with eXcel, and it looked to me that you can take the 20W50 plot and subtract 5 PSI across the board and know what 10W40 will do. I suspece that 0W30 will show a similar 5 PSI drop--time will tell. The interesting part was the lower oil temps on the track and consequently the higher idle oil pressure after a run on the track with 10W40 than 20W50. It is my suposition that the higher idle pressure and lower track temperature means that the lighter oil is doing at least as well in reducing friction as the heavier oil.

    A ferrari engine, unlike the big american V8s, has great big oil galleys, and moves around 2.5X to 3X as much oil through the engine. The F355 heads are cooled more by oil than by water, so moving a lot of oil here is reasonable. In addition, the back sides of the pistons have a continuous spray of oil to cool the pistons. Most of the oil galeys in the F355 engine would not be clogged if an entire pencil was somewho misplaced in the galley durring assembly <don't try this one at home>. The same cannot be said of American V8s.
     
  11. atlantaman

    atlantaman Formula 3

    Mar 31, 2002
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    HOW OIL WORKS....
    when a cam or crank spins it is actually "floating " from oil under pressure. The design is that metal should never thouch metal. There actually is a long set for defined steps that will allow you to calculate the exact viscosity oil you need at a given temperature--all based on things like bearing surface area, max rotational speed, shearing resistance of the oil,....

    IF YOU START USING THINNER OIL--YOUR CAMS AND CRANK WILL NOT HAVE THE DESIGNED "OIL LAYER THICKNESS" REQUIRED TO FLOAT THE SHAFTS PROPERLY AND YOU WILL BE PRONE TO PERIODIC METAL-TO-METAL RUBBING THUS RAPIDLY MAKING BAD PARTS OUT OF GOOD ONES.

    PS--in motor design--they usually start with the oil and calculate the bearing surface areas to match--not the other way around.

    I run 10-40 in winter and 20-50 in summer---2-3 HP extra is not worth the extra engine wear and tear.
     
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  13. AEHaas

    AEHaas Formula 3

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    Formula engines are relatively small yet have 2 to 3 times the horsepower. They use 5 and 10 wt motor oils. These engines run hotter and at higher RPM. The engines are good for multiple practice sessions and multiple races before needing some of the parts to be replaced. Even then replacement is not because the engines are useless but rather to keep HP to an absolute maximum. The smallest loss of compression is not acceptable.

    Lubrication in engines is oil flow and thinner oils flow better. Higher flow means cooler parts, means less wear on those parts. Also, since the engines run cooler, the oil does not thin out as much so it is never as thin as you may be afraid of.

    The actual temperature of that small amount of oil that is actually in the bearing or piston's ring surfaces is 300 to 400F. At his temperature 10 and 50 wt oil has about the same viscosity anyway, probably a 1 or 2 centistoke difference. At startup however, where almost all engine wear occurs the difference in viscosity is over 100 cs.

    aehaas
     
  14. 4re gt4

    4re gt4 Formula 3

    Apr 23, 2002
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    I'm glad someone else piped in with an opinion that just adequate pressure isn't *necessarily* enough.

    In the "olden days of yore", small block Chevys were often set up for racing with parts clearances that were measured with a yardstick. Even with super volume/pressure oil pumps and 90lbs operating pressure, it was still necessary to run as much as 50W (or sometimes more) to prevent problems. That we know for certain from experience at the circle track.

    Times change, and it seems that even on race engines clearances have tightened up considerably from what we used 40 years ago. So I don't doubt that thinner oil works fine --- to a point!

    Proper viscosity is a topic best left to the guy who designed the engine. My old GT4 specifies mud-like viscosity, and I'm sticking with it.
     
  15. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
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    So this might have been covered in the past, but my '77 308 engine oil sticker in the engine bay calls for 10W-50. Never seen such a thing. Given that 10W-50 is hard to find, which do you guys recommend, 10W-40 or 20W-50? I'm currently using 20W-50 but was thinking of using 10W-40 because it is much easier to find and you have a better selection of oils. I was thinking that the difference was going to be squat.

    Birdman
     
  16. jw6513

    jw6513 Karting

    Nov 24, 2003
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    Try Castrol Syntec 5w-50.....best of both worlds
     
  17. DGS

    DGS Four Time F1 World Champ
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    So what does a different weight oil do to the self-adjusting valve lifters in the newer engines?

    When oil is used as hydraulic fluid as well as a lubricant, things might be a tad more complicated.
     
  18. 355f

    355f Formula Junior

    Nov 1, 2003
    305
    interesting.

    You dont memtion what model you have but in the case of the 355 the manufacturers ask for shell 5/40

    Isnt it wise to stick to their suggestions?? how can we know better.?

    Actually, I did want to try castrol 10/60 but was worried about a change.

    Another point not mentioned about lower weight oils is that using say a 0 spec oil one does get more oil draindown aftre a stop
     
  19. AEHaas

    AEHaas Formula 3

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    Look at your oil temperature gauge. Note that it redlines at probably around 280 F. That is the temperature you would probably reach on the track. There you would need 50 or 60 wt oil. Around town my gauge reads around 185F, a hundred degrees cooler. These are street race cars and the manufacturer assumes you are racing around with a hot engine. If you drive as most owners, on the street and not the track then your oil is too cold and too thick.

    The general saying that 90 percent of engine wear and tear occurs in cold engines is close to the truth. The most basic viscosity needs are defined by a pressure of 10 PSI per 1,000 RPM at operating temperature. My 575 M manual states the target pressure is 74 PSI at 6,000 RPM. The oil supplied with the car gives me about 80 PSI at 2,000 RPM, way too high. FNA told me the cars are delivered with 5W-30 Helix. This is with around the town driving. I am sure that on the racetrack at full power and a hotter engine this thicker oil is fine. For my usual driving however, the thicker oil is causing more engine wear.

    The manual of my old 550 Maranello gave only Shell Helix Ultra 5-40 for all uses. Oils are not that versatile. For around town use a thin oil, for the track use a thicker one. The new 575 manual states that the oil should be 15-50 for racing and 0-40 for around town. They are finally making more sense.

    Oils are getting thinner. Ford now supplies most cars with 5 - 20 oil, previously it was 5 - 30. If you test different oils in your engine you will notice the engine oil temperature decreasing with thinner oils. At some point the next thinner oil will result in the engine temperature starting to go back up. This lowest temperature point is that with the least friction.

    A friend recently changed from Mobil 1 15-50 in his big SUV to Pennzoil 5-20 and went from 10 to 13 MPG around town. There was a slight decrease in engine oil temperature. The savings was also in cost for oil. His biggest enjoyment was the increase in get up and go power. For time trials all Indy and Stock cars use thinner oils to get more power. These oils will not stay thick enough for a long hot race but around the town driving is nothing like racing. The thinning of oil is not from wear but rather dilution from piston blow by of fuel.

    The last misconception I will tell you about is that those oil viscosity numbers on that oil can are not what you think at all. For example, Pennzoil 100W EP gear oil is almost the exact same thickness as straight 30W engine oil. The additives are different. 10-30 Mobil 1 is thicker at startup than 0-30 Mobil 1 but the 0-30 is actually thicker than the 10-30 with a hot engine. If you need a thicker oil with your hot engine the 0-30 is better than the 10-30 Mobil 1.

    In conclusion oil is a dynamic lubricant and the viscosity your engine needs depends on the temperature it is running to give you a certain pressure range. More pressure and less pressure is not desirable, you need the correct pressure for your application. Again, use one oil for the track and another for around town.

    aehaas
     
  20. ChrisfromRI

    ChrisfromRI Karting

    Jan 28, 2003
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    Danger -- Contrarian Viewpoint:

    The trend we have all seen in OEM oil recommendations getting lighter over the years coincides with the OEM need to produce cars with greater fuel efficiency while meeting tighter emissions standards. Accordingly, I believe that the trend towards lighter weight oils has a lot more to do with these issues, than with anything else.

    To be sure, the OEM could care less about engine longevity, so long as their engines don't wear out before the warranty period is up. In fact the OEM would be all too happy to sell you their expensive replacement parts/engines outside of the warranty period.

    Kind Regards, Chris
     
  21. dm_n_stuff

    dm_n_stuff Global Moderator
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    According to the mechanic who works on my Dino, synthetics will leak like crazy around the seals.

    I'm not sure I followed the reasoning, which I can no longer remember, but it seemed perfectly reasonable at the time.

    Just a thought on synthetics in motors that were not designed for them.
     
  22. AEHaas

    AEHaas Formula 3

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    From an earlier post:

    I do not have my SAE documents at hand so I am guessing. Remember that we are only dealing with the second number. When the engine is hot a 0W-30, 5W-30, 10W-30 or straight 30W oil have the same viscosity. The only hot data is at 212 F --

    2W is 3
    5W is 4 - 5
    10W is 5 - 6
    20W is 8 - 9
    30W is 10 - 11
    40W is 13 - 15
    50W is 18 - 20
    60W is 23 - 24

    They are not tested but at 2 temperatures, 104 F (considered a cold engine) and 212 F. Any other viscosity relation to a temperature would have to be an educated guess. At 290 F I would guess the viscosities are --

    2W 1
    5W 1.5
    10W 2
    20W 3
    30W 3.5
    40W 4
    50W 5

    Note that a viscosity of 0 is relative and not actually zero. It is a function of the scale and method used for measurement. Another example is the F and C scales of temperature. At zero degrees there is no absence of energy. The real and absolute temperature at zero C is actually 273 degrees Kelvin. At zero K there is no molecular movement. On the Celsius scale it is -273 degrees C, -460 F.

    Note also that the vis of 40W oil is 4 and 10W oil is 2. This does not mean that the 40 is twice as thick as the 10. It is just 2 centistokes thicker. This is almost no difference at all.

    As I said before, the viscosity differences are minimal at higher temperatures. They are substantial at lower temperatures where most wear and tear occurs. This is why they are using 2W, 5W, 10W and the like in high RPM and high heat formula engines.

    aehaas
     
  23. rob lay

    rob lay Administrator
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    Well, this warrants another thread and has been discussed a little before. When I switched to synthetic on my 328 I started getting a few more oil leak problems the first 6 months. Now that I addressed those few problems I actually have 0 leaks and don't have to add oil between changes. With regular oil I would get the "couple" drops a day and have to add a little oil between changes.

    The main problem I refer to is the oil leak in the rear distributor rotor cap where I lost spark on that bank.
     
  24. 355f

    355f Formula Junior

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  25. AEHaas

    AEHaas Formula 3

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    355f,

    You need to watch how you reproduce a post. It looks as if I posted everything above, including your comments.

    0W is less like honey at startup than a 5W or a 10W-X. We do not worry about residual oil upstairs but rather how fast new oil under pressure gets there on startup. The less honey like the faster (the right) pressure, flow and lubrication develops. Lubrication in engines is from the FLOW of oil only.

    The correct wt. oil for your application is not what I think but what your temperatures and pressures tell you to use. Re-read my previous posts. It states clearly what I found and what I did to correct it.

    aehaas
     
  26. f355spider

    f355spider F1 World Champ
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    As far as what FNA recommends for the 308/328/Mondial, Ferrari SPa recommended in 6/88 to use Agip SINT 2000 10w-40 (a synthetic blend, I believe) since they were no longer producing the 10w-50. service bulletin 00-25 dated 6/15/88. At a tech session summer of 2003 Ferrari of Seattle said that with few exceptions, the current Shell lubricants can be used in most all Ferraris produced since the mid 70's. That would sort of imply that Shell Helix 5w-40 synthetic would be what they would recommend now.
     
  27. Lawrence Coppari

    Lawrence Coppari Formula 3

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    "A friend recently changed from Mobil 1 15-50 in his big SUV to Pennzoil 5-20 and went from 10 to 13 MPG around town. "

    I think your friend needs a refresher course in arithmetic. A 30% increase in fuel mileage by changing motor oils....... Or he must drive downhill with Pennzoil and uphill with Mobil.
     
  28. AEHaas

    AEHaas Formula 3

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    Mobil 1 15W-50 Viscosity at 104F - 125, at 212F - 17
    Pennzoil 5W-20 Viscosity at 104F - 48, at 212F - 9

    The guy does a lot of short trips. Going from 10 to 13 is not unreasonable if you study these facts. The guy is an honest man and I believe him. He is very precise. He is the architect for my house (Mir a Vida) here in Osprey, Florida. I believe what he tells me.

    aehaas
     

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