Race prepped e36 BMW M3 (euro), choosing oil?

[nevaste]

I have a m3 which have a euro S50B30 engine (288hp) with Accralite pistons. I have been using 5w50 Mobil rally formula1. On hot day (33 Celcius) the oil pressure drops to 1.1-1.2 bar at idle and it lights my warning light (oil pressure warning starts at 1.2bar).

Do you have any suggestion what kind oil to use. I not keen to use 10w60 oil such as Castrol TWS do to the bearing tolerances in s50 engines. Also it rises oil temps quite lot

 

[Falcon_LS]

Welcome to BITOG.

I think I would take a look at oils such as:

RedLine 5W-40 High Performance Synthetic

Motul 300V Power 5W-40

Liqui-Moly Synthoil High Tech 5W-40

Millers CFS Competition 5W-40

Morris Multivis 5W-40

Morris X-RPM Competition 10W-50

Millers CFS Competition 10W-50

Fuchs Titan Race Pro S 10W-50

 

[nevaste]

Liqui-Moly 5w40 is easily available here. Why did you recommended that oil, is it suitable considering the heavy track use?

 

[BMWTurboDzl]

Nice ride!

 

[Falcon_LS]

Synthoil High Tech 5W-40 is basically Liqui-Moly's premium full synthetic. It carries Porsche A40 accreditation and is formulated with a heavy duty additive package for extreme conditions.

 

[d00df00d]

to BITOG!

Have you checked your PCV system? I once had a flickering oil pressure light at idle on hot days, and it went away after I replaced my PCV oil separator valve. It used to happen even with Motul 300V 5w-40; after that, it never happened even with a slightly sheared 0w-30.

 

[nevaste]

I have a oil catch can with return to oil sump. It breaths to athmosphere. So pcv is removed. I know that I had a slight cylinder pressure problem and hence the engine is now beeing rebuilt with those Accralite pistons mentioned in the first post. Pressure drop happened with old OEM pistons.

 

[rslifkin]

If it's being rebuilt, it should have new bearings as well. With a good 5W-40 in there, it should be just fine after the rebuild.

 

[ARCOgraphite]

Pistons should not affect gauge pressure - a bearing clearance may have been incorrect.

 

[d00df00d]

Originally Posted By: nevaste
I have a oil catch can with return to oil sump. It breaths to athmosphere. So pcv is removed.

If I'm not mistaken, my engine (US-spec) needs vacuum in the crankcase for the oil pressure regulation to work properly. I'm not sure if that applies to the Euro engine.

I've also heard that professional race engines and some performance street engines often use electric vacuum pumps because manifold vacuum isn't enough.

 

[nevaste]

well, I have heard that also, but haven't researched that so much.

is there any oil analysis regarding that Liqui-Moly Synthoil 5w40?

 

[d00df00d]

Before you consider a 5w-40, it would be important to understand what your current oil's viscosity is in your engine. The 5w-50 you have been using may have sheared, but you need to know how much; if it only sheared into the SAE 40 region, switching to a 5w-40 would not be too likely to affect your oil pressure. It may even worsen the problem if it shears, too.

Moreover, if you have doubts as to whether your crankcase pressure affects your oil pressure, you should determine that first before trying to address the problem through your oil choice. Only a thicker oil will increase pressure, and as you pointed out with the TWS example, thicker oil also increases temperatures.

 

[nevaste]

I saw uoa report of M1 rf 5w50 which indicated shearing to 40 oil. Thats not bad, since all other values were very good.

Do you have any info regarding the difference between Gulf competition and racing oils? Competition seems to be ester based?

 

[nevaste]

Hmm, I could not edit last post so I have write a new one.

even though I tried to search I did not find anything on CG TWS 10w60 oil? i would quess that it has been discussed alot here.

 

[d00df00d]

Originally Posted By: nevaste
I saw uoa report of M1 rf 5w50 which indicated shearing to 40 oil. Thats not bad, since all other values were very good.

Yes, but what is it doing in YOUR car? That's the question.

 

[d00df00d]

Originally Posted By: nevaste
even though I tried to search I did not find anything on CG TWS 10w60 oil? i would quess that it has been discussed alot here.

Put the following in a Google search:

site:bobistheoilguy.com TWS

You will find plenty of threads.

 

[nevaste]

Thanks! Seeing some UOA results it seems evident not to use TWS in my engine. My friend drives a rally car (e36 m3) and was using TWS and oil temp were 140C. After changing to Mobil1 RF 5w50 temps dropped to 120C

 

[d00df00d]

Originally Posted By: nevaste
Thanks! Seeing some UOA results it seems evident not to use TWS in my engine.

Why? I agree that TWS probably isn't needed but I'm wondering what you saw that led you to that conclusion.


Originally Posted By: nevaste
My friend drives a rally car (e36 m3) and was using TWS and oil temp were 140C. After changing to Mobil1 RF 5w50 temps dropped to 120C

Thinner oil means lower temps. I don't think you can always count on that much of a difference (there may have been other factors involved in your friend's case), but that's the trend.

 

[nevaste]

I´m not saying that TWS is a bad oil, but Mobil 1rf seems to have better additive pack than M1 rf. Even though it shreads t0 40 weight, it is still heavy enough for my engine. And, as I said it keeps the engine cooler. I only drive max 10 laps at a time (around 30-35km) at one stint and maybe 30-50 laps per session.

I´m open to alla suggestions and advise regarding the most suitable oil, but I´m not going to do UOA test of my own.

 

[d00df00d]

If you're not going to test your oil, no advice we could give you would be better than a blind guess. You might as well make a list of all fully synthetic xw-40 and xw-50 oils you can find and try them at random until you see the oil pressures you want.