10W-40

[rice_classic]

Originally Posted by b.e

Well, I don't know if this is true. The point of multi-grade oil is to make this not true. The cold viscosity ("0W" is lower than the hot viscosity ("-20") meaning the oil flows better when cold and thickens at it heats up. Whatever chemical properties cause this to happen (I'm a chemist and I don't know how they do this) might extend above the 100 centigrade test temperature. If they do, then what you say is false. If the inverted viscosity behavior fails at some point above 100 c and the oil starts acting like most other fluids, then what you say is be true.

Wish I could find out which it is.

For anyone reading this thread please take note that the quoted text above is not true.

Sorry b.e., not trying to rain on your parade but what you state is a common misconception about oil rating. Thanks for your understanding.

[rice_classic]

Originally Posted by Blighty

So the key seems for me to be that if you want to have a happy car on and after a track day, then you either keep the temp down, or use a thicker oil.

Eloquent, simple, accurate.

Originally Posted by Blighty

I'm sure that frequent oil changes are good too.

That's up to you. Oil analysis can help you determine that.

Check this out:
http://www.joegibbsracingoil.com/tra...h/filters.html
On my race car I used to change my oil/filter between every race weekend... talk about throwing money away. Now I go several race weekends but change filters.

On the converse:

In that other thread it will see it mentioned that this is a Direct Injected engine and some DI engines have a tendency to have some fuel get into their oil as a result. I don't know if this DI engine is susceptible to that but hence the need for oil analysis. I think changing at 3k is way overkill though, especially with how good modern oil is now including synthetics.

[b.e]

Originally Posted by rice_classic

Sorry b.e., not trying to rain on your parade but what you state is a common misconception about oil rating. Thanks for your understanding.

Thanks for setting me right. I've done a bit more work on the problem, and have found that the difference in the viscosity index numbers has some bearing on the b parameter of the variance of viscosity with temperature, viscosity= ue^(-bT) It's not a direct bearing, however.

The trouble, I think, is that the SAE defined two different indices for the cold and hot numbers. Dumb but true. 20W-20 is not a single-grade oil. Oils for other uses have their own indices, also. Alas, science and mechanics do not mix.

I'll fix my post above.

[smbrm]

For those of waded in, thanks. It doesn't seem as lonely!

And yes, all oils get thin when they get hot. Multigrading additives just mean they do not thin as much as temperature increases(And yes, that is an over simplification statement).


I may regret what I am going to say next:
One thing with an extra oil cooler is to consider one with a thermostat. (Not sure, I have never purchased one, they may all come with a thermostat?) That way the oil cooler comes into play when needed. Running an oil too cold(below the dispersant activation temperature) can cause something, rare but possible, called cold sludging where the oil does not get hot enough for the dispersant to work properly and then can lead to degradation that can cause the oil to thicken over time similar to what you get when an oil sludges from being too hot.

The thermostat also protects the cooler during start up until the oil has warmed up.

[Blighty]

Originally Posted by smbrm

I may regret what I am going to say next:
One thing with an extra oil cooler is to consider one with a thermostat. (Not sure, I have never purchased one, they may all come with a thermostat?) That way the oil cooler comes into play when needed. Running an oil too cold(below the dispersant activation temperature) can cause something, rare but possible, called cold sludging where the oil does not get hot enough for the dispersant to work properly and then can lead to degradation that can cause the oil to thicken over time similar to what you get when an oil sludges from being too hot.

The thermostat also protects the cooler during start up until the oil has warmed up.

Haha, no I think you're safe

Yes, I definatly don't want cold oil (regardless of the 0w), proper operating temp please.

God, I'm already anal about warming up my war, imagine the wait I might have if I'm actively keeping it low before I get going!

Originally Posted by rice_classic

Eloquent, simple, accurate.

You are too kind! I just decided to take smbrm's first post and use that as a source of truth, then kept reading websites.

Originally Posted by rice_classic

That's up to you. Oil analysis can help you determine that.

Check this out:
http://www.joegibbsracingoil.com/tra...h/filters.html
On my race car I used to change my oil/filter between every race weekend... talk about throwing money away. Now I go several race weekends but change filters.

On the converse:

In that other thread it will see it mentioned that this is a Direct Injected engine and some DI engines have a tendency to have some fuel get into their oil as a result. I don't know if this DI engine is susceptible to that but hence the need for oil analysis. I think changing at 3k is way overkill though, especially with how good modern oil is now including synthetics.

I'm only halving the service interval for oil change (every 7500km), when I track it, I think I'll do the same as you and change filter when at the track. Seems like a good idea. I'm hoping that with temperature controlled a little, the oil life should be fine.

Racing might be a different matter. Tracking I can stop after a few laps, change some stuff. Racing you cant really stop! I hope to do a few hillclimbs, but I don't expect that to be too bad.

Anyway - many thanks to all that assisted with my questions.

[serialk11r]

Originally Posted by rice_classic

Eloquent, simple, accurate.

In that other thread it will see it mentioned that this is a Direct Injected engine and some DI engines have a tendency to have some fuel get into their oil as a result. I don't know if this DI engine is susceptible to that but hence the need for oil analysis. I think changing at 3k is way overkill though, especially with how good modern oil is now including synthetics.

EDIT: Okay nevermind couldn't find it, but I'm not sure how much higher temperature say 40 or 50 weight oil can take and still maintain 20 weight oil (at more reasonable temperatures) viscosity, I have a feeling it's not that much. Also, thicker oil naturally picks up more heat as a result of increased friction, though I imagine this is not a big effect (could be wrong). The biggest argument for thicker oils that I've seen on BITOG is that sliding surfaces under high pressure (i.e. cam lobes) don't receive pressurized oil and so thick oils actually do protect them better, but this engine's valvetrain has rollers so it's not as big of a deal or something.

I also doubt the DI fuel dilution thing is true. By design DI is supposed to place more fuel towards the plug and away from the cylinder walls since the fuel has less time to mix and vaporize at low engine speed.

[ZDan]

Originally Posted by serialk11r

EDIT: Okay nevermind couldn't find it, but I'm not sure how much higher temperature say 40 or 50 weight oil can take and still maintain 20 weight oil (at more reasonable temperatures) viscosity, I have a feeling it's not that much.

You'd run thicker oil at the track not to preserve its viscosity after it cools back down from elevated temps, but to have the appropriate viscosity at elevated temperatures. I.e., if your oil runs up to, say, 275F at the track, a 30, 40 or 50 weight oil is going to be a lot closer to the right viscosity than a 0W20, which might be dangerously thin at that temperature.

(Obviously you'll want synthetic if you are running elevated oil temperatures, whatever weight you run.)

[smbrm]

Originally Posted by serialk11r

EDIT: Okay nevermind couldn't find it, but I'm not sure how much higher temperature say 40 or 50 weight oil can take and still maintain 20 weight oil (at more reasonable temperatures) viscosity, I have a feeling it's not that much.

1) &&W-40 and &&W-50 oils, particularly with higher && of 15 or 20 can have much higher HTHS than 0W-20. And remember viscosity changes logarithmically with temperature, no linearly.

Originally Posted by serialk11r

EDIT:
Also, thicker oil naturally picks up more heat as a result of increased friction, though I imagine this is not a big effect (could be wrong).

2) It generates more heat due to internal friction and power required to move something thick.

Originally Posted by serialk11r

EDIT:
The biggest argument for thicker oils that I've seen on BITOG is that sliding surfaces under high pressure (i.e. cam lobes) don't receive pressurized oil and so thick oils actually do protect them better, but this engine's valvetrain has rollers so it's not as big of a deal or something.

3) Agree partly, except a large proportion of the protection for flat tappet sliding cam follower interfaces comes from the antiwear additive that will oxidize in the interface to form a phosphorous(in the case of ZDDP) protective layer.

ZDDP is also a very cost effective antioxidant whose function has to be taken over by other formulation solutions as ZDDP has been reduced.

Roller followers significantly reduce friction in this area. This design feature contributes to better fuel economy and/or power. It also allows other antiwear solutions that reduce phosphorus that is considered to have long term negative impact(via oil consumption) on catalyst life.

Like I have said before, engine oil formulation is a big balancing act of multiple requirements.

But I am probably suggesting things more complicated again!

[smbrm]

Originally Posted by ZDan

You'd run thicker oil at the track not to preserve its viscosity after it cools back down from elevated temps, but to have the appropriate viscosity at elevated temperatures. I.e., if your oil runs up to, say, 275F at the track, a 30, 40 or 50 weight oil is going to be a lot closer to the right viscosity than a 0W20, which might be dangerously thin at that temperature.

(Obviously you'll want synthetic if you are running elevated oil temperatures, whatever weight you run.)

Your bulk average oil temperature should not normally be that much more than your coolant temperature, however as I have said before the temperature in the connecting rod bearings and shear loads and resulting film thickness are what is important to bearing protection.

[serialk11r]

Originally Posted by ZDan

You'd run thicker oil at the track not to preserve its viscosity after it cools back down from elevated temps, but to have the appropriate viscosity at elevated temperatures. I.e., if your oil runs up to, say, 275F at the track, a 30, 40 or 50 weight oil is going to be a lot closer to the right viscosity than a 0W20, which might be dangerously thin at that temperature.

(Obviously you'll want synthetic if you are running elevated oil temperatures, whatever weight you run.)

Right, I'm just speculating that at say 275F, a 50 weight still might not be "within spec". I haven't looked up any data but on BITOG there's a chart saying that 30 weight oil is about 3cSt at 300F, which is much thinner than the 7-8 cSt of 20 weight oil at 212F.

And even with synthetic you would want to be careful about oil temps since the oil does cool the piston and stuff like that which are much hotter than the average oil temp and can oxidize the oil quickly.

[smbrm]

Originally Posted by serialk11r

Right, I'm just speculating that at say 275F, a 50 weight still might not be "within spec". I haven't looked up any data but on BITOG there's a chart saying that 30 weight oil is about 3cSt at 300F, which is much thinner than the 7-8 cSt of 20 weight oil at 212F.

And even with synthetic you would want to be careful about oil temps since the oil does cool the piston and stuff like that which are much hotter than the average oil temp and can oxidize the oil quickly.

Not trying to be provocative, but I am curious as to what spec. you are referring to when you say "...still might not be within spec......"?

[serialk11r]

Originally Posted by smbrm

Not trying to be provocative, but I am curious as to what spec. you are referring to when you say "...still might not be within spec......"?

So 20 weight oil at operating temperature (a bit over 100C?) is about 7cSt, right? I wonder how hot 50 weight oil can get before it drops below that. Aka, how much hotter can you run 50 weight oil before it's as thin as 20 weight oil at a given temperature, in the range of usual oil temperatures seen in a car engine.

[ZDan]

The pertinent question is: What is the viscosity of the oil at operating temperature. *IF* under track usage, oil temperature gets as high as 280F, then a 20weight is going to be at ~3cSt, while a 15w40 is going to be ~7-8cSt.
At least according to this chart (which I cannot vouch for).

Knowing what the operational oil temperatures are would be required to know what viscosity to run. Without knowing oil temps, I would tend to go at least one range higher in viscosity for track days. Running a 5W30 in these cars even at very cold temperatures isn't going to be as risky as running 0W20 at 250+

I've always just run 10W30 (factory spec) synthetic in the s2000. But in the LS2 RX-7 I run 40wt (vs 5w30 factory spec) in the warmer months when I will be tracking it as a hedge against high operating temperatures.
Really need to get an oil temp gauge though. For all I know I should be running 15W50...

[bluesubie]

Originally Posted by ZDan

Knowing what the operational oil temperatures are would be required to know what viscosity to run. Without knowing oil temps, I would tend to go at least one range higher in viscosity for track days. Running a 5W30 in these cars even at very cold temperatures isn't going to be as risky as running 0W20 at 250+

The operational viscosity of most 5W-30's will likely be in the range of a 20 grade anyway. For track use, an oil pressure gauge is a fantastic tool in trying to select the proper viscosity.

-Dennis