Relationship between Oil Temperature and Oil Pressure | FerrariChat

Relationship between Oil Temperature and Oil Pressure

Discussion in '308/328' started by Brian A, Oct 6, 2014.

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  1. Brian A

    Brian A F1 Rookie

    Dec 21, 2012
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    1983 US 308 GTS QV
    The inland San Francisco Bay Area is experiencing extremely hot weather for October. By midafternoon yesterday ambient temperature was about 95F (35C).

    I took my ’83 QV for a long (50 mile / 80 km) spirited back roads drive in the heat of the day. Mostly 3rd gear travel kicking to 4th on straights just to stay at legal speeds to the next corner. Oil temperature was above the 210F (100C) marker and water temp was a little above the 195F (90C) marker. Nothing too high.

    By the end of the drive, both low and high RPM oil pressures had crept down below numbers I am used to. At higher RPM, usually the needle is closest to the 85 psi marker; yesterday I was much closer to the next marker down. Is this Normal Vehicle Function or does this indicate that my oil viscosity dropped too low for those driving conditions? I am using xW40 synthetic engine oil. Does moving to xW50 oil affect oil pressure much?

    Toward the end of the drive, my speedometer had begun to operate erratically (dropping to show what appeared to 1/2 speed or 1/4 speed) (…one more thing to fix) so, I suppose, this could just be a gauge accuracy issue.

    Thoughts?
     
  2. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Water temp was a little high and I'd suggest seeing what can be done to make that system work a little better. Above middle is OK idling or crawling around town but on the road at speed it really should go down a little below middle.

    The oil temp was fine. Modern oils have a safe operating range far higher than the old gauges suggest. The pressure is always highly suspect. The gauges are so often wrong, a bad joke really for an expensive sports car. I'd put a mechanical gauge on it and get some good baseline numbers with hot oil. We are in the same area and I see no reason to go over 40w oil unless it is a track day.
     
  3. Crowndog

    Crowndog F1 Veteran

    Jul 16, 2011
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    Reviving this to get an idea of what a proper oil temperature should be. For example; I am putting an auxiliary oil radiator fan on my car, what is the ideal temp that the thermostatic control should turn on the fan?


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  4. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    You won't get much difference with an oil cooler fan. I have had a switched puller behind mine for about 15 years. Never made much difference. Traffic, track, nothing.
     
  5. TacElf

    TacElf Formula 3
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    It is my understanding that 100C considered the normal fully-warmed-up oil operating temperature. As Rifledriver mentioned, actually measuring this on the somewhat myopic gauges/senders in these cars can be a point of frustration or humor depending on how you look at it.
     
  6. ClydeM

    ClydeM F1 World Champ
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    I've been interested in putting a fan on the cooler for years. I decided to revive this project and went looking from Tommy's old post.
    Can't figure out where the beginning is, but here is some pics & details:

    Partial broken link
    Better link into the bowels of Ferrari chat
    FerrariChat.com: ATTENTION 308 OWNERS: OIL COOLER FAN INSTALLED LOOK!!!
     
  7. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    I forgot about that old thread. Well, after many many years of real world testing by me, sadly it never really lived up to my headline.

    I would rather have it, than not, though.
     
  8. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    Wow, that was over 18,000 posts and nearly 12 years ago.
     
  9. ClydeM

    ClydeM F1 World Champ
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    Yah. We're getting old (er) :)

    So you don't think it really does anything for the car, huh?
     
  10. chrismorse

    chrismorse Formula 3

    Feb 16, 2004
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    I tried one and it made no perceptible change street or the occasional track.

    heavier oil, (x-50) for hard use/track.

    chris
     
  11. Rifledriver

    Rifledriver Three Time F1 World Champ

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    At low speeds when the fan might do some good it isn't needed. At high speeds when it might be needed it will actually inhibit air flow.

    How high is the temp? The gauges were designed for oil made in the period. Modern synthetic oils can safely be operated at 320 or more degrees. Can't read anything near that high on a 308 or 328 gauge.

    The only Ferrari of the period with an oil temp problem was the BB's.


    Bottom line?

    Quit worrying about it.
     
  12. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    I think the concern really isn't if the modern synthetics can handle the heat. I think the question that needs to be investigated is why is it getting so hot to begin with.

    As long as the water temps remain within normal limits, do we need to worry about a high oil temp reading or worry about the cause and disparity with the water?
     
  13. Peter

    Peter F1 Veteran
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    Dec 21, 2000
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    #13 Peter, Jun 22, 2015
    Last edited by a moderator: Sep 7, 2017
    I have a fan on my oil cooler as that's how it came - I adapted an aftermarket B&M cooler to a bracket and duct I custom made, to replace the original (leaky) cooler.

    I found that the fan kept the oil TOO COLD. It was considerably colder than the water temp (so probably in the 180 degree range VS. 195-ish for water, according to the gauges ;) ). I wired that fan on a switch when I installed it, because I expected I would need to shut it off when I would drive it in the winter. I kept driving with it off in the Spring, then in the Summer and haven't turned it back on since. Temps now are roughly the same for both water and oil.
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  14. st@ven

    st@ven F1 Rookie

    Aug 4, 2008
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    320 is indeed pretty high. Brian, i do understand that modern oils are able to work on these temperatures. ( we actually hade a similar thread a couple of years ago and you mentionned this exact same number) But, as these oil temperatures were not possible in the cars back than, is there any other tresshold? Meaning, is there any part of the engine that cannot handle these temperatures?

    With other words, if the oil itself is not the weakest link anymore, what is next?
     
  15. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    Why would oil be a "weak link" at all? The cars ran fine on the oil produced back in the day. Why would anyone expect that the oil used now has to somehow be "better" in order to work properly? The fact that oil it IS better now is a different, and unrelated, issue.

    It seems a lot of time is spent hand wringing over non problems. These cars didn't need a fan on an oil cooler when new. If it needs one now, something is, as they say in the technical world, "broke." Fix that.
     
  16. ClydeM

    ClydeM F1 World Champ
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    I have a water temp issue when the car isn't going > 40mph. Here in the NorthEast, there's so much traffic and humidity that it's frequently near or in the red.
    I've chased it down for years to no avail.
    When the car was at a shop that preps Ferrari challenge cars and other race cars, the mechanic suggested I forget about the water & put a fan on the oil cooler as that is what really matters and if the oil was cool, the water would follow. That's when I became interested in Tommy's solution.
     
  17. Crowndog

    Crowndog F1 Veteran

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    In my case with the modified motor (remember close to 350hp) I was concerned that perhaps the oil cooling capacity of the stock configuration wasn't up to snuff. So I am thinking of adding the aux fan for those hot days and hot running. Don't want it running in cool weather so a thermostat control seems appropriate.
    Brian I suppose I need to do some hot weather testing to see if it's really needed at all.
    To those that have done this modification , great projects you did. Thanks for posting!


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  18. Rifledriver

    Rifledriver Three Time F1 World Champ

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    Cooling of either water or oil was not an issue on those cars. Address the symptom you have and do not reengineer the car.
     
  19. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    Problems surface over time. When these cars were new, they only needed belt changes every 50,000 miles....

    When I installed the oil cooler fan on my car back then, it was to *try* to calm high oil temps on the track. My car would peg the oil temp after 20 minutes of 7700 rpm shifts, especially at TigPrix. Water temps really never increased.

    As the years went by, I found myself trying to use it to cool the car in traffic. Mine has a tendency to run hot if not moving and it has always done this in the 18 years I have driven it. That is another subject.

    The fan never really worked that well. Maybe a little but not enough to feel like I found a solution.

    So anyway, I never worried about the oil's ability to handel the heat stress, I was worried about outher things such as the cause and elements of the car that, perhaps, wouldn't be so happy with an oil temp pegged all the way to the right.
     
  20. mike996

    mike996 F1 Veteran

    Jun 14, 2008
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    "When I installed the oil cooler fan on my car back then, it was to *try* to calm high oil temps on the track. My car would peg the oil temp after 20 minutes of 7700 rpm shifts, especially at TigPrix. Water temps really never increased. "

    Certainly, if you are tracking/racing a car, the load on the cooling systems - oil and water - are quite different than they are for street use so, like virtually any street cars, some mods may be needed for that use. Also, if the motor is now modified to produce considerably more HP, more heat is generated for the oil/water systems to dissipate which is beyond that of the original design.
     
  21. Rifledriver

    Rifledriver Three Time F1 World Champ

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    What is a high reading? I have yet to see where anyone here has mentioned an oil temp number that was in anyway worthy of worrying about by any standard. I reread the thread to be sure I didn't miss anything and 210 is the only number mentioned. That is certainly not high. It is considered minimum by some to keep moisture from accumulating.

    If and when high temps are experienced I suppose it can be a topic of discussion.
     
  22. ME308

    ME308 Formula 3

    Nov 5, 2003
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    as long as the systems works as designed, there is no need for an oil cooler on a street driven car - never even thought of one

    yub, I always considered 210 as "engine warm" ;)
    have been driving with those temps for the last 35000 miles -
    since the engine is still running, my consideration can not be that wrong :D
     
  23. ClydeM

    ClydeM F1 World Champ
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    agreed - find/fix the problem. I'm just out of ideas. But I'll resurrect an older thread rather than detour this one. TY.
     
  24. Dr Tommy Cosgrove

    Dr Tommy Cosgrove Three Time F1 World Champ
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    Back in my early years with the car I was unfamiliar with it and its personality in general. The hot oil temps on the track was not alarming to me - the reason was obvious, I was just trying to come up with a way to cool it off while I was out there.

    Once I realized the fan wasn't going to make any difference, I just forgot about it from then on. The only time I flipped the switch was when I was stuck in traffic and all the needles started heading to the right.

    If the pros in this thread say it isn't going to hurt anything, I'm good. Nothing to worry about.
     
  25. Crowndog

    Crowndog F1 Veteran

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    I agree but am still left wondering if higher oil temps cause higher water temps? If cooling the oil a bit helps overall engine temps in those gridlock hot days city driving wouldn't it help?


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