RTS and elevated oil temps

[synormin]

I posted this at the Shell Rotella site but got no replies so I'll give it shot here. Let me know if more info is needed. Thanks!


Hi All, Recently switched oil in my '76 911S to Rotella 5W40 and have noticed an increase in my oil temperature. Now along with this oil change I did a valve adjustment, which came out beautifully and reset the ignition timing to where it had been previously, 5 degrees ATDC (factory spec for my CIS 2.7 motor), idle speed 950 rpm. Also summer is now in full force in the Northwest so I expect my air/oil cooled motor to run warmer when there's warmer weather but I'm noticing these elevated temps even on cool morning drives (5AM) to work (25 miles). An important point I should mention is that my oil pressure is textbook for a 911 motor, 10lbs of oil pressure per 1000 rpm...I'm right there. By the way the elevated temps I speak of are well within safe limits, just over 210 degrees today on the way home. I'm pleased with my decision to switch to Rotella Syn just curious if there's a reason for what's happening. Thanks!

 

[turbodieselfreak]

I think there's several factors to consider here. What weight were you using before and what brand? Synth or non-synth? Have you been driving it harder since the oil change? FWIW, I've used RTS and delvac 1 in my diesel app, and it actually seems to prefer the RTS-runs smoother, and the wear on the drain plug appears to be one hair less.

 

[synormin]

Yeah I figured that there are other elements at work here too. Prior to the RTS I was using 10w40 LubroMoly MOS2 Anti-friction oil which my 911 seemed to like...as opposed to the oil before that, which was 15w40 Swepco 306. With the 15W40 winter time starting seemed harder than it should, that was my reason for the switch to 10W40. After reading all the posts here about RTS it seems like a good choice...good price, readily available, robust additive package, etc and my 911 seems to like this oil too!
My driving style has remained basically the same so I wouldn't factor that one in heavily as a reason. Curious.

 

[turbodieselfreak]

You air cooled guys do seem to benefit from the dual rated oils. As long as the engine feels as smooth as you're used to, I wouldn't worry about the temp increase- do a UOA if it concerns you. Just a guess, but I'm thinking maybe the RTS is more efficient at carrying heat away from the moving parts, showing a temp increase at the gauge. I use it in the 6.0 powerstroke. If your familiar with diesels, you know the injection system on this engine shears oil like crazy, and I haven't had any oil related failures. I think you'll be fine.

 

[synormin]

Thanks for your advice of this turbodieselfreak, it seems like a logical explanation and one that I like the sound of. I didn't think that the RTS was allowing more friction in my motor and thus raising the temps, at least I hoped not! It's my understanding that Porsche used an HDEO as the factory fill for many years in the 911 based cars, and I think it was a Shell product also.
What is it about those Powerstroke motors that shears the oil, something with the oil pump (think I read that here)? Thanks again!

 

[cosynthetics]

They run a high pressure oil pump which is used to fire the injectors.

 

[DB_Cooper]

I have a 86 3.2 911 and have run Rotella 15w40 in the summer and RTS in the cooler months. My engine temps were up slightly this past summer too. I believe it is the fuel rather than the lubricating oil. The 10% ethanol mix makes for a warmer engine. I also have a 1974 Laverda 1000. With the newer fuel I have had to retard the timing, enrich the mixture and go to a cooler plug. After 30 years with the bike, there is no doubt the fuel is changing the operating environment for the engine. With DME on the Porsche, tuning is less available. On your engine, you may want to look at the timing and mixture.

 

[Doug Hillary]

Hi,
synormin - Shell was the supplier to Porsche for many many years including when the 911 was introduced. The lubricant was Rotella/Rimula. It was this way until around the late 1980s. The HD lubricants used were SAE20W-20, SAE30 and SAE40 and later 10W-40, 15w40 as I recall. The HD specifications commenced with CAT Series 3 and MIL as the baseline - these was the most reliable ones around at the time - no ACEA then and a "care less" API too

The factory uses HDEOs in its Museum based air cooled cars except when "racing"!

Many reasons are possible for "slight" variances in lubricant temperatures in Porsche air cooled engines