On street cars with oil temp gauges, I've always seen higher temps with heavier oil [all things equal]- it must not transmit the heat as well, and has higher internal friction.
Heavier oil = higher temps??
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silverz06vette
Great to see a post from a member that actually has an oil temperature and oil pressure gauge.
If we take as fact that M1,0w-40 is closer to a '30',then is it fair to assume that the higher running oil temp is from the '0' component as opposed to the '40'?
Great to see a post from a member that actually has an oil temperature and oil pressure gauge.
If we take as fact that M1,0w-40 is closer to a '30',then is it fair to assume that the higher running oil temp is from the '0' component as opposed to the '40'?
I have a stock stat that opens at about 194°, I have the fans programed to come on at 183°. At the time I had a 180° stat but it failed and I reinstalled the stock one.
Water temps are about 210° max if I remember right. Water usually stays around 190-192° while cruising on the highway. The stock fan settings are approx 19x° for the low speed fans and 228° for the high speed fans.
About 3 years ago I was at Roebling Road near Savannah, GA for a track event. A few other Z06s where there and most of us had peak oil temps of about 275-285°, one guys oil temp was like 315°+. I asked what oil he was running and he said Mobil 1 15w-50. I told him IMO I thought thats why his oil temps where higher. He could not understand it, "how could that be if its a better oil?"
I'm thinking about having the Mobil 1 0w-40 in the car when I get to VIR in July and running one day with it. Then change the oil for the next day to Mobil 1 10w30. It will be kind of a PITA, but then I would know. Just have to hope that the OATs are about the same both days. Then again it was cooler on sunday as it rained early in the morning and was cloudy for most of the day. I think the high temp might of got to 85° or so. It was at least 92° and sunny on sat. Oil temps where the same on both days.
[ May 04, 2005, 12:41 AM: Message edited by: silverz06vette ]
Water temps are about 210° max if I remember right. Water usually stays around 190-192° while cruising on the highway. The stock fan settings are approx 19x° for the low speed fans and 228° for the high speed fans.
About 3 years ago I was at Roebling Road near Savannah, GA for a track event. A few other Z06s where there and most of us had peak oil temps of about 275-285°, one guys oil temp was like 315°+. I asked what oil he was running and he said Mobil 1 15w-50. I told him IMO I thought thats why his oil temps where higher. He could not understand it, "how could that be if its a better oil?"
I'm thinking about having the Mobil 1 0w-40 in the car when I get to VIR in July and running one day with it. Then change the oil for the next day to Mobil 1 10w30. It will be kind of a PITA, but then I would know. Just have to hope that the OATs are about the same both days. Then again it was cooler on sunday as it rained early in the morning and was cloudy for most of the day. I think the high temp might of got to 85° or so. It was at least 92° and sunny on sat. Oil temps where the same on both days.
[ May 04, 2005, 12:41 AM: Message edited by: silverz06vette ]
The journal bearing design equations are based on decades of emperical data. There is no need to play the blind man and elephant to figure out what is going on.
Oil pressure above 4000 RPMs was essentially the same xW30, xW40, and xW50 at 95 PSI to 100 PSI (hot). The xW50 oil was up 3-5 PSI in this rev range compared to the thinner oils (Track hot).
The only real difference came when leaving the track with hot oil and idleing through the pits. Here the thicker oil was both hotter and had a lower idle oil pressure.
The pressure to RPM relationship held the same with all the oils (up to the oil pressure pop off valve opening) its just that the xW50 oil, when track hot, started at a lower PSI and had farther to go.
I have a plot of the oil temp to pressure relationship at:
http://www.ferrari-talk.com/discus/messages/5/5001.html
The car may have seemed a bit happier with the thinner oil. And by this I mean the note from the engine not in any sense of power delivery.
Water temps were essentially the same within 2dF--I might note that the transmission oil to engine water 'oil cooler' puts a lot of the transmission heat into the engine water.
I don't understand the mechanisms involved, only the data points.
Mitch
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Okay, I'll accept this as fact ..just because I know you don't talk crap
I do find some assertions lacking in material proof however. For example the assertion that since you run a thinner weight oil ..it will result in lower oil temps. This is kinda incomplete since you don't know if the temp should be lower due to higher rejection/dump rate of the oil or if it should be higher due to it's ability to allow heat to migrate to it. If you had an insulated sump how would that alter the results/perception??
I don't see how anyone can differentiate between thermal conductivity and thermal production and thermal retention. These are factors that are unkown to just about anyone outside the lab.
For the sake of real world discussion here ..let's say I run a 20w-50 vs a 5w-20 in near identical conditions and they both result in near identical oil sump temps at highway speeds. What's my take on it since my only apparent difference is oil pressure?? What compensatory mechanisms are at work here to make this possible when all other things appear equal?
Could it be that the thicker, denser oil has the ability to contain more thermal energy and thus actually cools the engine parts more effectively?
If an oil is very thick, more energy is required to run the oil pumping process than when the oil is thinner. Here the movement of oil through the engine is adding heat to the oil.
If an oil is very thin, then internal friction (sliding, scraping, and wiping) add heat to the oil (and wear to the engine). Here, the heat is generated at the point of lubrication to the oil.
So there should be a happy point in between where measured temperatures are lowest. The spread between xW50 and xW20 is great enough that either a xW30 or xW40 might result in lower temps than either of the more extreme oils.
Thinner oil runs off the hot engine parts faster, carrying away heat. It also transfers heat faster, especially if some cooler is installed. Finally, less energy is required to circulate it. OTOH, you reach diminishing returns at some point, which is why 40 is better than 50 but also 30 here.
Interesting info. Thanks Mitch.
Interesting info. Thanks Mitch.
This is why I think a 5W40 synthetic or semi-synthetic is the ideal comprimise for 90% of daily drivers! Unlike a 5W20 or 5W30 with a 5W40 you get the good cold weather cababilities of any 5W oil but you also get enough HTHS to make sure you are well covered for any type of unforseen event. I have proofed Redline 5W40 down to -18°F in a 03 Camry! I am sure it would handle 100°F or hoter ambient temp's just as well!
All oils have their place but some products just scream great comprimise like a well engineered 5W40!
In a track envirment I think I would definately try SX-UP from specialty Formulations to try to get the friction and heat down with a great additive package instead of trying to rely soley on viscosity!
All oils have their place but some products just scream great comprimise like a well engineered 5W40!
In a track envirment I think I would definately try SX-UP from specialty Formulations to try to get the friction and heat down with a great additive package instead of trying to rely soley on viscosity!
Thinking out loud....as others have commented at the oil pump the flow should be similar for cold or hot or thick or thin oil, losses due to thin oil leaking past pump clearances aside, the oil being thin due either to viscosity and/or temperature. Oil flow 'downstream' would also be the same is one was measuring at the end of an an oil tight line. Flow varies at the point where pressure is measured in an engine due to the multiple paths where an oil could leak past clearances, as oil doesn't compress much, and a thinner oil will leak thru more clearances.
Thinner oil tends to provide better heat transfer, but if it's cooler at one point in an engine is it due to the engine running cooler or because it has already shed a lot of heat ? If thin oil provides better heat transfer because it flows over surfaces easier, why doesn't the thick oil that is actually thinner at the higher temperature, remember the pressure was lower, do the same ?
It still seems that we need a measure of engine temperature in order to determine if it's actually running cooler.
Thinner oil tends to provide better heat transfer, but if it's cooler at one point in an engine is it due to the engine running cooler or because it has already shed a lot of heat ? If thin oil provides better heat transfer because it flows over surfaces easier, why doesn't the thick oil that is actually thinner at the higher temperature, remember the pressure was lower, do the same ?
It still seems that we need a measure of engine temperature in order to determine if it's actually running cooler.
Just curious, which 5w30 did you use that has this high of an HT/HS? RL?
Yes.
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I'm not disputing your assertions here ..but it does kinda remind me of that (either) Greek or Roman paradox between the Lawyer that taught another law on the condition of being paid upon the winning of his first case (I forget the principles names). The student delayed going into practice and was sued for the fees. His position was that if he won the suit, then by court decree, he didn't owe the fees. If on the otherhand he lost in court, then he didn't win his first case, and therefore didn't owe the fees due to their agreement. The Plaintif had a reciprocol arguement.
"It still seems that we need a measure of engine temperature in order to determine if it's actually running cooler."
oooh, real data instead of endless supposition? how much fun is that?
This is the internet, it's no place for real data....
oooh, real data instead of endless supposition? how much fun is that?
This is the internet, it's no place for real data....
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Yes. Rad delta T would be an indicator ..but only if you could index it for flow (both internally and cfm across it, also indexed for temp). That's why I think anything outside of a lab you would have a hard time isolating what elements were passive/sympathetic indications or of more direct/primary type.
Absolutely!! This isn't science! This is philosophy.
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