old school M1 15w-50 red cap vs 15w-50ep for track use

[silverz06vette]

A friend has his Z06 stroked out to a 383, the engine builder recommends M1 15w-50.

What do you guys think of the New 15w50ep with its HTHS of 4.4 compared to the old 15w-50 and its HTHS of 5.1? Any disadvanage to either? What about in the cooler months?

The car will be tracked but does have an oil cooler and sees about 265° oil max with the old setup which was a head and cam car.

Does anybody have the cSt @ 40º C for the old 15w-50?

Thanks!

 

[427Z06]

The red cap 40C viscosity was 125 cSt. IMHO, 4.43 HTHS of the EP version should be adequate for the application mentioned.

 

[silverz06vette]

quote:

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Originally posted by 427Z06:
The red cap 40C viscosity was 125 cSt. IMHO, 4.43 HTHS of the EP version should be adequate for the application mentioned.

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So being that the new 15w-50s cSt @ 40º C is 133, would that even make a better case for the red cap? I mean you are getting a higher HTHS #s and better flow at startup. Or do I have it all wrong?

Thanks!

 

[Mitch Alsup]

I think that either oil will be just fine;

Since you have an oil cooler, and the oil is stabilizing at 265dF under track conditions, either 15W-50 oil might be a tad thicker than optimal.

My Ferrari F355B ran 280dF temps with old M1 15W-50 at TWS in the heat of summer, and now runs 265dF temps with M1 5W-40 in the heat of Texas summers.

You might want to try an M1 15W-50 oil for one track day and then try a 5W-40 oil for a different track day. Stick with the oil that gives the lower track oil temperature and/or the higher idle oil pressure after a lapping session.

 

[427Z06]

I concur with Mitch's approach. Let good data be your guide to the optimum combination.

 

[silverz06vette]

Thanks guys!

I will pass this info on to him.