1992 Mazda Miata 12 Hour Endurance Race

[Koko & Bros]

Attached is an oil sample from our 1992 (1.6) Mazda Miata Racecar. This was from a 12 hour endurance race plus approximately 1 hour of practice prior to the race. Oil was SN rated Kendall SAE30. Curious to see where You think there is room for improvement? Oil pressure indicates 48-52psi while racing (stock relief pressure), based on this I operate under the assumption that a 40wt will reduce flow, therefor reducing cooling and protection? Look forward to Your comments!

 

[zeky]

When ws the engine last rebuilt?

 

[BMW Dom]

The 40wt will not reduce flow.

 

[Koko & Bros]

Unknown miles on the unit. Leakdown is a little high on cylinder 1 but strong on 2-3 & 4. Wear metals looked very good from oil analysis I have done on previous BMW M20 engines in the same racing environment.

 

[PimTac]

Very interesting and thanks for sharing.

 

[ctechbob]

Those motors are so easy on oil and so near bulletproof even when banging them off the rev-limiter that I don't think going any thicker is going to get you anything other than more heat into the oil from pumping losses.

 

[Koko & Bros]

What are the thoughts of going to a synthetic oil? The reasoning for the sae30 is shear stability which clearly worked seeing that viscosity is 9.5 with 1.5% fuel. If I want to a multigrade I feel a 40wt is in order. My other feeling for a synthetic oil is that we get this car warm and dog on it for hours and then dump the oil, cold viscosity is irrelevant.

 

[MacManus99]

Does 92 have a real oil pressure gauge, or is it a dummy gauge? If you're still showing 48-52 psi at racing temps, then I would think you could afford to drop to a w20 oil, and maybe pick up a tiny bit of power by doing so. Lord knows those B6 engines need all the help they can get. Run a racing specific oil and change after the race.

I ran 15w40 HDEO in my BP4W, but that was a mixture of both street and track usage. IF it was a dedicated racecar, it would have received dedicated race parts and consumable.

 

[Koko & Bros]

Does 92 have a real oil pressure gauge, or is it a dummy gauge? If you're still showing 48-52 psi at racing temps, then I would think you could afford to drop to a w20 oil, and maybe pick up a tiny bit of power by doing so. Lord knows those B6 engines need all the help they can get. Run a racing specific oil and change after the race.

I ran 15w40 HDEO in my BP4W, but that was a mixture of both street and track usage. IF it was a dedicated racecar, it would have received dedicated race parts and consumable.

Real oil pressure gauge. I have no interest in gaining power from oil, only longevity. The engine already makes 125whp

 

[MacManus99]

Real oil pressure gauge. I have no interest in gaining power from oil, only longevity. The engine already makes 125whp

That's fair, I would then recommend running a Xw40 dedicated race oil. I would start by changing it after a 15 hr interval, send for UOA, and extend to 26+ hrs from there. Everything with oil is give and take. Race oils provide high temp and rpm protection, at the cost of a shorter interval. Street oil increase this interval, usually at the cost of cost of something else. Engineering 101, there is no best at everything, you can't have your cake, and eat it too.

PS: Enjoy the car, you're using it in it's natural habitat. I sure as hell miss mine.

 

[Koko & Bros]

I was going to try rotella t5 10w30 for our next race. Does anyone predict better wear numbers from a synthetic hdeo or a synthetic sn/sp 40wt?

 

[edyvw]

I was going to try rotella t5 10w30 for our next race. Does anyone predict better wear numbers from a synthetic hdeo or a synthetic sn/sp 40wt?

One option is to go Mobil1 0W40FS. Zinc is around 1,100ppm, HTHS at 3.6. It is not too thick but offers superb protection and it is common in these environments.
But, I personally would go Motul 300V. 5W30 has HTHS of 3.5 and 5W40 some 4.1. I think in your case 5W30 would work well as based on this UOA there is no too much shearing. It is dedicated racing oil, ester based.

 

[ctechbob]

PS: Enjoy the car, you're using it in it's natural habitat. I sure as hell miss mine.

Same here..