Thicker oil runs hotter so I end with the same protection due to lower viscosity?

[RDY4WAR]

I assume you mean retard the timing. Why would retarding the timing cause more heat? I would think that advancing the timing would cause more power and more heat. Don't know. Just curious. Lower octane fuel is higher power fuel so that would cause more heat I guess. All other things equal.

Delayed ignition means the fuel is still trying to burn later into the power stroke. The rate of thermal decay is slowed with more heat radiating (wasted) to the piston, rings, and cylinder walls (and coolant). It also increases EGTs and contributes to valve and valve seat wear, specifically more so on the exhaust side. It reduces cylinder evacuation of spent gases and heat, increasing residual cylinder temperature and reversion during overlap. It's why retarding ignition timing reduces intake vacuum and creates a rougher, less efficient idle.

Many OEMs delay ignition timing during the warmup phase for this reason. It brings the engine and coolant up to temperature faster. The spark then advances to a more ideal range once near operating temperature.

Several years ago, a friend brought his early 80s FSB by for me look into an overheating problem. It had a 388W (351W w/ 3.75" stroke and +0.060" overbore) and he couldn't keep the temperature down at low speed around town and while idling. It would cool down once on the highway, but sitting a long light, the coolant temp would creep to 220+°F. He put in a bigger radiator with better fans cutting on a lower temperature and a high volume water pump to try to stop the issue, but it would still creep up. His engine builder told him it was because the block was bored +0.060" and there's nothing he can do about it. (that's a myth, btw) The first thing I looked at was the vacuum advance on the distributor and saw it was on ported advance. I moved the hose from ported to a manifold source, which increased his idle spark advance from 10° to 22°, and it stayed at 190-195°F after 20 minutes of idling.

A lot of gearheads still screw this up and want to put no vacuum advance or ported advance on their classic car and hot rod because that's the way the OEM had it. The OEM did it because it hastened warmup and reduced nox emissions. If you're not trying to warm up the engine in the cold of winter or trying to pass a tail sniffer, you're just making the engine prone to overheating for no benefit.

 

[PontiacHO]

I assume you mean retard the timing. Why would retarding the timing cause more heat? I would think that advancing the timing would cause more power and more heat. Don't know. Just curious. Lower octane fuel is higher power fuel so that would cause more heat I guess. All other things equal.

Judging semantics are used typically when unsure of a topic but still want to find issue with what’s being said. Lower-Retarded timing will generate more heat in an engine. It has been explained wonderfully within this thread.

 

[Cujet]

Do certain oils just run cooler? Even similar viscosity? If so, what are the factors that would cause one oil to run cooler than another?

I read this thread with interest. Been there, done that.

Absolutely some oils of the very same viscosity will run cooler in road racing applications. Don't let those who don't race or work on race cars tell you otherwise. PAO's were well known for lower temps, even with higher viscosity. There are even differences in an oil's thermal conductivity and specific heat capacity, this affects the oil cooler capacity and more.

Initial impression: Your model is known to have oil temp issues on the track. I know you have a big oil cooler, and 200ºF cooler thermostat. That may not be enough. Another thought, keep your coolant low on antifreeze concentration, (use water wetter) and make really sure your cooling system is not struggling. Water and oil temp are related.

I'd like to see your oil temps at or near 220. It may not be easy, but that's pretty much where you should be. As to lower viscosity getting you there, won't happen. Lower film strength is highly correlated with higher oil temps when at the limit.

 

[FZ1]

I just recently went thru a little experiment with wife's 1.5 GDI-Turbo. Been running 0w30 most of the last 6 months. One could see the very first time I started it after the change from 0w20 that temp gage went up very fast to the normal range like never before. So I have noticed each day upon her return from work (about nine to ten miles) when she parks in the garage you can feel the extreme heat being thrown off and could barley touch the "white" hood. Now the temp reading is always right at normal. Cooling system working fine and the fans kick on and off. So I replaced the oil Monday with 0w20 out of my stash. I have HPL 0w20 and 0w30 stored. The very next afternoon when she arrived I went out to check and the car was not throwing off near as much heat and one could easily feel the hood not near as hot. I have no explanation. Not an engineer , chemist or some kind of lubrication expert. All I know is what I just experienced this week. So, I have been reading as much as I can about this across the internet. It is wild. I can tell one that there is an equal amount of write ups on the subject that will say "NO , it does not affect or cause a hotter engine." Then keep looking and one can find an actual equal amount who say, "YES it can affect the under hood temperatures." Both also mention they are talking about vehicles with correct , proper working and well maintained cooling systems.

Now, her car is not and never has run hot according to the gages. No issues what so ever. Just a matter of always throwing off lots of heat after driving. I have altered the use of higher and lower viscocity oils in so many of our vehicles over the years but never a turbo and never experienced or noticed what I have with this car's engine.

The answer is certainly complex and there is not a simple YES or No to the question. This comes right off the internet and the interesting thing is that while there is no date I can see , but it actually has a BITOG stamp at the bottom. What the +5 means?

Can Higher Viscosity Motor Oil Cause Overheating?
Higher viscosity motor oil can potentially cause overheating if the oil is too thick for the engine's operating temperature. When the oil is too thick, it can hinder oil flow and lead to overheating. However, the impact of oil viscosity on engine temperature is complex and can be influenced by various factors, including the engine's cooling system, driving conditions, and the oil's quality. It is essential to use the correct viscosity oil for the engine's needs to prevent overheating and ensure optimal engine performance. Bob is The Oil Guy +5.
https://www.bing.com/ck/a?!&&p=f811...1ZS10by1sb3dlci12aXNjb3NpdHkuMzk5MTk1Lw&ntb=1

Cooler's better than Hotter in the Sunny South. Go with your experience.

 

[Cujet]

Just another thought. You could use thermocouples carefully taped and tied on to the oil cooler inlet and outlet. Your setup with thermostat may be bypassing or unable to flow enough through the cooler. You'd see this as cool oil on the cooler outlet. But very hot engine oil in general.

Put another way, the flow rate through the cooler should be epic good, with large lines and no restrictions. In the vast majority of cases, it is not true that the oil can flow too fast through a cooler (unless we consider the OEM water to oil units with zero surface area) While oil does not transfer heat instantly like water, PAO's heat transfer thermal conductivity of 0.14–0.15 W/m·K, and specific heat capacity of 2.0–2.2 kJ/kg·K are as much as 10% better than a group 3 oil.

 

[TiGeo]

Seems odd to have any meaningful differences between these 2 oils on track. Your comment about the 5W-40 being thicker is not accurate...they're both 40 grades (leave the winter rating out...it's not a viscosity) and I believe here the M1 0W-40 has a higher HTHS so "thicker" when hot.

You can look around here and find the viscosity vs. grade graphs/calculators to answer the question and see which oil at a given temp has a higher viscosity.

There has been some testing/data/logs presented by the European VW track folks that showed 30 grades running cooler on track than 40 grades (Euro oils here in turbo VWs).

The only correlation I see for my car w/r to oil temps on track is ambient temps assuming the nut behind the wheel variable (lap times) are similar - how hard I'm pushing.

If the M1 0W-40 worked why not continue running it? The grade/viscosity question you had isn't valid here because they are both for all intents/purposes the same.

 

[Carlostrece]

Combustion heat is largely contained to the chamber which is the main point. You want that heat driving the piston down, not escaping by it or radiating away from it. If that much heat was escaping the chamber into the oil, IC engines would be even less efficient than they already are. You ultimately still get some combustion heat into the oil as it splashes on the pistons and cylinder walls, but this is a small contribution comparatively.

While using a more viscous oil does help with preventing metal to metal contact, there's a point where this is null. You can't subtract from zero. If 3.3 cP will provide sufficient wedge and keep the crank journal centric, with no boundary contact, going to 3.8 cP will just increase fluid drag (hydrodynamic friction) for no positive trade-off. It won't magically make the bearing clearance wider. As rpm increases, so does the friction, and thus the heat as well.

View attachment 297884

View attachment 297885

That is a more detailed and scientific way of saying what I said earlier. I said thicker isn't always better. Thinner isn't always better either. What's best is the appropriate viscosity (whatever that may be for this engine and driving style).

In the spirit of experimentation, learning, and the chance that it might be as good or better... I think the OP should try a Euro spec 5w30. It might be the best option.

Also, as someone said earlier, the OP could change oil back to M1 0w40 to see if his temps goes back down.

However, now we're at end of summer. There's not much time left for these experiments.

 

[kschachn]

However, now we're at end of summer. There's not much time left for these experiments.

If the oil is the source of the temperature increase then why would this make a difference? He’s claiming that despite any environmental differences or any difference in driving habits, the oil is the sole cause of the discrepancy.

 

[Carlostrece]

If the oil is the source of the temperature increase then why would this make a difference? He’s claiming that despite any environmental differences or any difference in driving habits, the oil is the sole cause of the discrepancy.

Yaaa... Well... I don't believe that ambient air temp has no effect. I believe to get apples to apples comparisons of different oils, he'd need to test/compare them on days with same ambient air temp.

Such as 3 days that are all 75F, or all 80F, or all 90F. Consistency of air temp is needed as a control. If each oil is tested in different weather/air temp then nothing can be learned, IMO.

For that matter, consistency of as many factors as possible. Ideally the only difference should be the oil. Then he can learn how each oil does with oil temp.

I'd like him to takes notes on how Castrol Edge 5w40, Mobil One 0w40, and a good Euro spec 5w30 do for oil temp and track time on 3 dry days with same temp and similar humidity.