What oil for 1991Porsche 911 Cup, race car?

[oliver88]

i race a 1991 Porsche Cup Car 911 with a 3.6 liter air cooled engine. it will regularly operate at oil temp's of 240-250 for 30 minutes to an hour....what oils should i consider using??

Thanks and i always enjoy the wisdom form this site!!

 

[Steve S]

Probably a real well additized syn oil.

 

[drums57]

Valoline 20w50 VR-1 racing oil.

 

[benjamming]

What oil(s) have you used in the past?
I would suggest reading up on Redline.

 

[oliver88]

i have used redline 15w50 and castrol syntec 5w50...car currently has schaffers new 5w40 in it...runs cooler than it did with the previous two oils....they seem to create more heat in the oil? the previous owner ran mobil 1 15w50 but the car was operted in a cooler climate, plus this Ohio summer has been extremely hot,95 degrees two weekends ago at nelson ledges.

 

[oliver88]

any suggestions with old UOA's would be terrific! car holds 13.5 quarts and i will submit a UOA at the next oil change in mid-august

 

[Steve S]

Porches are real neat cars especially the air cooled ones "911" Years ago one of my friends had a 1976 or 77 turbo I really liked it in fact probably to this day my favorite, the car made go fast noise and in fact it was fast.

 

[jsharp]

quote:

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Originally posted by oliver88:
i have used redline 15w50 and castrol syntec 5w50...car currently has schaffers new 5w40 in it...runs cooler than it did with the previous two oils....they seem to create more heat in the oil? the previous owner ran mobil 1 15w50 but the car was operted in a cooler climate, plus this Ohio summer has been extremely hot,95 degrees two weekends ago at nelson ledges.

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It doesn't surprise me that the 40 weight runs cooler than the 50 weight. I've seen the same thing with air cooled motorcycle engines.

 

[Doug Hillary]

Hi,
I would suggest you stick with the Porsche Approved grade (5w-40) and a full synthetic lubricant (Porsche Approved and/or ACEA A3/B3 quality rated

A synthetic 5w-40 HDEO will perform well in these engines and at these temperatures. They will however NOT be Porsche Approved. Their advantage is in viscosity retention, deposit control, volatility and foaming control (just like a Porsche Approved lubricant)

Regards
Doug

 

[TooSlick]

I'd agree with Doug and I'd run the Amsoil 5w-40, which they specifically recommend for Porsche factory fill requirements.

If you run this engine extremely hard, I'd also consider the Amsoil, Series 2000, 20w-50. I've had excellent results with this oil in older, high mileage German cars and sometimes run it in my 1990 Audi 100 in the summer in Alabama. I think you'll find it out performs the oils you've previously used as well.

The best Mobil product for this application ( in terms of high temp, high shear viscosity), IS their Delvac 1, commercial engine oil. As Doug mentioned, it does not technically meet the ACEA A3 specification. However since this car is long out of warranty, I'd be concerned about performance first and foremost.

TS

 

[FowVay]

I realize that my post is simply anecdotal but I have spent time in the workshop of Franz Blam and watched the preparation of numerous Porsche Cup race cars. The exclusive oil that they used in the air cooled engines was Mobil's 15W-50.

It might pay to send them a e-mail (address found at franzblamracing.com) and pose your oil question to them. They might be able to shed some light on the reasoning for this viscosity and brand of oil or steer you in the right direction to find your answer.

 

[Mitch Alsup]

quote:

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Originally posted by oliver88:
i have used redline 15w50 and castrol syntec 5w50...car currently has schaffers new 5w40 in it...runs cooler than it did with the previous two oils....they seem to create more heat in the oil? the previous owner ran mobil 1 15w50 but the car was operted in a cooler climate, plus this Ohio summer has been extremely hot,95 degrees two weekends ago at nelson ledges.

---

This is exactly the same result I got when I track my F355, the 5W-40 (and/or 10W-40) oils would operate at lower temperatures than the 15W-50 (and/or 20W-50) oils. My test was performed in the heat of Texas summers (105dF in the shade).

Run the oils weights that end up with the lower operating temperatures.

 

[oliver88]

will i record higher wear with the 40 weight vs. a 15w50? i have noticed that almost everyone is using the 15w50 Mobil 1, but when i ask them why, they really don't have any reasoning for their choice. i am trying to find one exceptional oil for this application and then stick with it for the season....i have really learned alot from the people on this site!! keep the idea's coming!

 

[Mitch Alsup]

The rest of my story::

When I would leave the track after a long hot run, the idle oil pressure back in the paddock was higher with the xW-40 oils (45 PSI) than with the xW-50 oils (35 PSI). This tells me that the 'thinner' oil was operating at a higher kinemetric viscocity than the 'thicker' oils. The drop of 15 dF (from 280dF to 265dF) was more than enough to make up for the 'thinness' of the oil.

So, if you have both an oil temp guage and an oil pressure guage, you can simply measure the results.

{Note: this experiment was conducted with 3 different xW-50 oils and 3 different xW-40 oils and 1 xW-30 oil. The difference between xW-50 oils was unmeasurable, the difference between the xW-40 oils was unmeasureable, and the xW-30 oil resulted in oil consumption issues at the track, so I discontinued this portion of the test. All oils were from M1, RL, and AMSoil}

 

[ebaker]

With an oil temp of 250° I'd run a 50 weight syn such as M1 15w50EP.

 

[Mitch Alsup]

quote:

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Originally posted by ebaker:
With an oil temp of 250° I'd run a 50 weight syn such as M1 15w50EP.

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But what would you run if the xW-40 oil came off the track with a 235dF temp while the xW-50 oil came off the track with a 250dF temp?

 

[bbcmat]

Best advise in the tread was to get hold of 3 teams that race that body style with that drivetrain under those conditions - and get their recommendations and reasons for it. Offer to pay if required.

If you don't see the motors apart during rebuild - you can't properly assess the oils you're using.

IMO

MAT

 

[quick_16]

I would ask Terry Dyson for a recommendation and do what he says. Asking other team is just the monkey see monkey do method and may not be the best oil at all. I see that a great deal in the drag racing I do. The other option is to Call Royal Purple or Red Line and ask there opinion and why. If you do not want to run a synthetic oil for some reason, the Schaeffer's Dino oil work very well and at a reasonable cost. ie 1/3 the cost of the good stuff mentioned above.
With the operating temperatures you gave I'd say a syn oil is required because that may be the average temp in the pan but the that same oil will see way hotter conditions as it moves in the engine. I think you want the higher temp margin that a syn will provide.
disclaimer:
This is just the spin from another racer and not an oil expert. I make well over 1000hp every time I run and found oil Terry's advise is worth the fee he may want...

 

[bbcmat]

Trust the monkey that successfully builds/rebuilds and R&Ds YOUR style of motor, doing YOUR style of racing. You will have to interpret what "successfully" means. (endurance vs performance vs cost)

I have to be on the first stage of nitrous to make (barely) that magic 1000hp - but I drove my package 4.5 HOURS last weekend visiting friends and going up to the coffee shop - mixed highway/city. I'll do this for the rest of the summer and well into the fall - check lash a couple of times and change the oil a couple of times too. Durability like this didn't come a special secret oil - it evolved from an engineered package built by professionals that KNOW and UNDERSTAND this application via EXPERIENCE and R&D. It USES a specialized oil (which I explored replacing with an alternative - that how I got to BITOG) because It works for this builder and is proven in this sort of application by successful rebuilds/inspections.

Take a cardiologist (engine mechanic) over a urologist (oil sample) for chest pain - even though they are related and complimentary disciplines.

IMO

MAT