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

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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.

 

[Carlostrece]

Are Z cars driven or raced in Japan? If so, what oil do they use? Does the car maker have recommendations for oil for racing?

 

[RDY4WAR]

Consistency of air temp is needed as a control.

I agree that close control of variables is essential for reliable and repeatable data. However, I have data on 2 NASCAR engines from 2 races at Daytona in different seasons. Comparing 65°F ambient temp in February with 96°F ambient temp in August, the difference in oil temperature is indiscernible.

 

[chris719]

I agree that close control of variables is essential for reliable and repeatable data. However, I have data on 2 NASCAR engines from 2 races at Daytona in different seasons. Comparing 65°F ambient temp in February with 96°F ambient temp in August, the difference in oil temperature is indiscernible.

I think that presumes a very capable cooling system. My M2 comp would sit at 100 C oil temps and basically not move no matter how you thrashed it, but not all cars are like that.

 

[scrllock]

Are Z cars driven or raced in Japan? If so, what oil do they use? Does the car maker have recommendations for oil for racing?

Yes, but this is somewhat irrelevant given the motor is built. OP doesn't mention bearings but it would be strange if they were re-used with aftermarket rods/pistons.

If it were a Nissan Motorsports car, it would be filled with 0w30 Motul.

https://www.nismo.co.jp/en/products/competition/of/competition_oil/lineup/0w30.html

Unless OP is really racing and has dedicated budget for motor rebuilds, I would stick to a 40 grade for safety. If oil temps are actually a problem, address them with an oil cooler. Also dedicated data collection like @Cujet suggested. A rough "runs 30 degrees hotter" isn't useful unless you know where and when it is running hotter. I'd much rather correlate my oils temps to average throttle and ambient temps, which is difficult without good datalogs.

 

[Cujet]

If it were a Nissan Motorsports car, it would be filled with 0w30 Motul.

We successfully use very low viscosity oils in road race cars. But I promise the oil temps are 100º lower than what the lightly modified street cars see when doing track days. Professional cars, professional results.

 

[Brian123]

Controls are the temps are 20-30 hotter with this oil in cooler temperatures.

I never broke 265 with this same setup in 100F weather.

This year never broke 90F and I'm running hotter.

Seriously? Just assume I cna not find a pattern.
This was a true waste of time to post

I agree 100%, this was a true waste of time for you starting this Thread, and the reason is that you did not do your homework. This is an Oil Forum, not a Track Car or race around the place forum. Your car is a V6 that holds maybe 5.2 quarts of oil.

8300 rpm's, you need more oil, 5.2 quarts of oil is not cutting it. Have you modified the Oil Pan? Have you thought about an Oil Accumulator? Have you ever heard about an Oil Accumulator? Do they make an Oil Pan for your car that has Baffles and a Trap Door?

This engine you have in your car is not set up for what you are doing with this car. A Wet Sump Oil System needs some help like I mentioned, you need a Dry Sump Oil System for the track driving you are doing.

 

[Hohn]

If I was seeing 30 degree oil temperature differences between to 40 grade Euro spec oils, I'd question the data and need to go do another "A" on the A/B/A test to confirm it. A simple A/B often is insufficiently reliable.

If the temp delta is real, I would ordinarily posit that the most likely explanation is that the Castrol is foaming. Foamed oil sucks as a cooling medium and foaming makes temps get toasty very fast. But it seems unlikely to me that any A3/B4 would have significant foaming, so I'm left shrugging my shoulders a bit.

If you have the oil pump capacity for it, a 0w-30 could be worth trying as long as it's a C30/504/507 rated oil with HTHS>3.5. Many of the 40 grade Euro oils have very little additional HTHS over the 30 grades and won't offer much of any increase in bearing films at speed. And the slightly thinner oil will have a bit less viscous heating while still having a good high flow rate that should help with hear rejection

Or even better, try one of the HPL NO VII Euro formulas like their 10w-30. Under racing conditions, it will have similar-to-thicker oil films than the M1 0w-40, and the full SAPS add pack gives you good add pack content. The NO VII 10w-30 is an HTHS of 3.6 and the M1 0w-40 is honestly about the same once it shears a bit.

I suspect the HPL 10w-30 No VII will run cooler than M1 even while offering essentially the same or better protection, despite the slightly lower 30 grade KV100. Higher density, but perhaps a bit higher flow, zero foam, great add pack.

Beyond that, your into dedicated racing oils. I'm spitballing here, and will readily defer to those with racing experience, though.

 

[Hohn]

This engine you have in your car is not set up for what you are doing with this car. A Wet Sump Oil System needs some help like I mentioned, you need a Dry Sump Oil System for the track driving you are doing.

QFT. This is exactly the case, IMO. The dry sump will add some much needed capacity, while delivering all the sorely-needed benefits that made dry sumps a thing to begin with. (windage, less viscous heating, less air entrainment, etc).

 

[scrllock]

We successfully use very low viscosity oils in road race cars. But I promise the oil temps are 100º lower than what the lightly modified street cars see when doing track days. Professional cars, professional results.

Sure, most actual race cars have very good cooling. Who knows how well the Z in question is set up in terms of ventilation, radiators, etc.

Now people are giving random advice about what his car might need for oil starvation, etc. That's going into wild speculation territory.

I'm curious why OP wouldn't just go back to M1 0w40. Those oil temps are nothing for that oil and it's cheap/widely available. If you need to change/add oil at the track, M1 0w40 is probably the best option you can find at a nearby store.

 

[Japanese]

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.

Well, the OP wrote on the first page:

Controls are the temps are 20-30 hotter with this oil in cooler temperatures.

I never broke 265 with this same setup in 100F weather.

This year never broke 90F and I'm running hotter.

 

[burbguy82]

Context: I have a track car and these temperatures are from circuit racing.

Car is 2007 350z with slightly built VQ35HR. Cams, lights eight rods and pistons, tune.
8300 rpm redline

I used to run 0w-40 M1
Temps were around 245-255F after half an hour in track where it leveled out.

Switched to Castrol 5w-40 euro.
Temps are now 275-285F after half an hour

So a thicker oil viscosity. But there is so much more heat from the higher viscosity that I almost think it actually ends up thinner.

Am I actually better off running a 5w-30? Would it run even cooler?

I feel like a thinner oil at a lower temperature would be better than a thicker oil at a higher temperature.

What is your opinion?
More importantly, what are facts you have to back it up?

It could be the thicker 5w40 oil is removing more heat from the engine. I would not correlate temp to protection level, nor would I say that 285 is hot. Cooler, may not be better.....

If I had a track car, she would get an oil change every track day = no issues