Oil weights...

[motogman]

So... What is the collective thought and comment on oil weights? I am looking at getting a couple of cases of Sweepco 306 and am debating between 20-50 and 15-40. I am looking at using this oil in three different Porsche engines; A stock 72 2.4 L w/ 83k miles, an 81 SC 3.0L stock with 60k miles and a 86 3.2 L track car with ??? miles.

I have generally thought that heavier weights were better as I do not run the cars much in the cold weather. But it is also not so often that I drive in that hot of weather. Some questions...

1) Is there much difference in the oil reuqirements for the 2.4, the 3.0 and the 3.2 L motors?

2) For the track car (3.2L) am I better off going with a single grade (w40 or w50) rather than muti grade?

3) What temperature does the typical 911 run? My 81 SC 3.0L which is more of a regular driver, just gets above the lower temperature gage band when running on the road?

4) What are the units and measures on these spec?? cSt is centi stokes I believe and cP is likely centipose? What is SUS? How do these relate and what is the criteria for low temperatures versus high temps?

Oh my... another oil thread...

The Swepco specs are below:

SAE Grade .................................... 5W-30 ....... 10W-30 ..... 15W-40 ......20W-50
Density, lbs/gal ............................... 7.23 ............ 7.30 ........... 7.34 ................ 7.4
Density, kg/l ................................... (0.868) ...... (0.876) ....... (0.881) ....... (0.888)
Viscosity, SUS @ 100 o F ................. 348 ............ 384 ............. 507 ............... 950
Viscosity, SUS @ 210 o F .................. 63 .............. 63 ............... 73 .................. 93
Viscosity, cSt @ 40 o C ...................... 75 .............. 75 ............ 109.4 .............. 206
Viscosity, cSt @ 100 o C .................. 11.9 ............ 11.9 .......... 13.74 ............. 18.5
Viscosity, cP @ - 15 o C...................... - .................. - ............. 3,500 ........... 3,000
Viscosity, cP @ - 20 o C...................... - .............. 3,500 ............. - ....................... -
Viscosity, cP @ - 25 o C.................. 3,500 .............. - ................. - ....................... -
Viscosity Index ................................ 150 ............ 145 ............. 135 ............... 125
Color .............................................. purple ........ purple ....... purple ......... purple
Pour Point o F, Max (oC) ............... -31 (-35) .... -31 (-35) .... -27 (-33) ..... -4 (-20)
Flash Point, COC, o F, Min (oC) ... 392 (179) .. 405 (207) ... 430 (221) 430 (221)
Total Base Number ......................... 10.3 ............ 10.3 ........... 10.3 .............. 10.3

[HarryD]

From what I have been able to find out, all air cooled 911 engines have the same oil requirements.

For most of the US, 20W-50 is the oil weight of choice. Good from -10 C to over 40 C (15 F to over 110 F). Are you expecting really low temperatures?

From the '84 Owners manual:



Of course, we will not discuss Zn, P, and TBN. There is already a very long thread on that topic.

[LOVEHZ]

Would be ok to mix weights? I use 20w50 conventional oil and was thinking of adding a few litres of 25w50 racing oil to get the Zn and P.

[slodave]

I use 40 wt year round. There are only one or two times that I drive the 911 when the temps are below the recommended temp range above around these parts though.

[Flieger]

Which 40 weight is that, Dave?

[LOVEHZ]

Looks like the owners manual answered my question about mixing the weights. Does anyone know what the difference between racing oil and conventional oil might be? About 2000ppm Zinc in the racing oil to start with.

[slodave]

Originally Posted by Flieger

Which 40 weight is that, Dave?

Shell Rotella T. There's a local distributor in town I go to. I can get everything from single gallons to 55 gal drums. I opt for the quart cases. I also pay cash, as they tack on a 3% charge if you pay by CC.

[HarryD]

Originally Posted by LOVEHZ

Looks like the owners manual answered my question about mixing the weights. Does anyone know what the difference between racing oil and conventional oil might be? About 2000ppm Zinc in the racing oil to start with.

Do what you wish but good oil is more than Zinc. You need for the detregent package to match the need as well. Each oil maker has his own "secret" formula to ge the correct balance of wear resistance, cleaning action, foam control, etc. Mixing brand A with Brand B may get you the ZDDP Level but screw up the other properties.

Spend your money on a good oil that has what you need and forget the alchemy.

[Brorag]

told by speedwerks rebuilder to run straight 30wt. We're in NC, so it doesn't get too cold.

[DRACO A5OG]

Originally Posted by slodave

I use 40 wt year round. There are only one or two times that I drive the 911 when the temps are below the recommended temp range above around these parts though.

Hey Dave, is that single weight? 40W?

[slodave]

Yes....

[DRACO A5OG]

Originally Posted by slodave

Yes....

Thanks brother Dave, I am thinking of going to STRAIGHT 40 weight since PAG is now recemmending 0W40 or 5W40 for all post '70 Porsches per Excellence Magazine article.

[slodave]

Hmmm... I switched over about 7 years ago. Ahead of the curve I see.

[DRACO A5OG]

You always were , especially infront of everyone at Willow , in our class

[motogman]

Is there much differnce between a 2.4 and a 3.2 in terms of oil needs? There were lot's of changes (improvements) in the 3.2 but what about oil needs?

Also - for track use I would think a straight 40 or 50 wt with the appropriate additive packages would be better than multi weight - ????

[DRACO A5OG]

The 0W40, I am thinking of has the needed Zinc/Phosphorus (trying not to create another Ultimate Oil Thread) so I will not need to add anything in my 3.2.

I am no expert, but I think it would be fine for your 2.4, but it will depend on your ambient temps per PAG Spec on recommended weight of oil.

[Quicksilver]

Steve Weiner, John Walker, Charles Navarro, etc... We have had continuous discussions with constant input from these experts and they have given us a list of oils that will allow us the greatest lifespan of our cars (even if the EPA could care less).
When the people who deal with a huge quantity of knowledge, deal with a huge quantity of engines, and have put a serious focus on this issue come up with very specific recommendations it may be a really good idea to listen to them. Especially when the only sign of a problem comes a long time after you have started to cause irreparable damage and the cost of a mistake is $10K+.

The recommendations have all been 50 weight multigrade oils: 20W50, 15W50, and even a 5W50 have been recommendations.


You can run a straight weight oil but the reason those aren't recommended is that it is very rare that people won't start putting some kind of load on their engine during the warm up period where the multigrades show their worth. If you are doing the initial break in of a motor then sure... go straight weight. If you are sure you will always putt-putt around until the temp is to the 1st line go ahead. If you know enough to make a decision that isn't what one of the experts have recommended then hopefully you really have a good reason and know what you are doing. (and you wouldn't be asking for advice here would you!?)

Otherwise get a good 50 weight multigrade that has been shown to have the correct level of zddp and has and additive package that is good for street use.