Motor Oil Viscosity Questions......

[Johnny-5]

Im about to do an oil change on a 2000 Porsche 911 (996) and Im hearing different types of viscosity motor oil answers so I just wanted some clarifications on things.

I have Mobil 1 Full Synthetic 10w30 and was told that is ok to use for all around weather but Im also told I should use 5w30 instead. Most people Ive talked to said 10w30 and 10w40 is the best to use for California temperature since it can be used all season.

Can someone tell me what they would recommend on our cars. Also when you start getting higher in mileage should we be using something higher or less in viscosity?

The car has about 40k on it.

Thanks,

Johnny

[RFM]

Porsche factory fill is Mobil 1 0W - 40. A lot of owners use Mobil 1 5W - 50 in turbo's, GT 3 and Cayenne GTS come alternative over here.

[White987S]

I would only use a 0W40 or 5W40 synthetic oil. One that is Porsche approved (there are many beyond Mobil One too).

5W50 Mobil 1 might also be an good choice, and is the only Porsche approved 5W50.

I would NOT use a 10W30 or a 5W30.

Change the oil at least once per year or every 7,500 miles.

[Johnny-5]

Thanks for your posts. Correct me if Im wrong....the first number is based on how cold it gets and the second on how hot it gets? Here in California it doesnt ever get in the negatives or even lower than 20F during the winter and during the sumer heats it could get over 100F but around this time getting close to fall and all its floating around 85F but usually lower. So if living somewhere alot colder and not getting as hot 0w40 makes sense.

So with that said and done wouldnt 10w30 or 10w40 should be fine???

Can some clarify or explain why I still should use something lower. I just need clarifications.

Thanks again.

[Loren]

What does the SAE Viscosity rating on your motor oil bottle mean?

[flyingpenguin]

What does the SAE Viscosity rating on your motor oil bottle mean?

You need the higher number to be at least 40 for the hydraulic valve lifters to work properly. I am in Houston, TX and use Mobil 1 15W50 Extended Performance all year round. It has 1200 ppm of ZDPP, which is good for added protection at high loads (eg. track days).

Joost

[ecgross1]

Our Walmart in Arizona carries Mobil 1 15W50 racing oil, which nobody buys, so it was on sale for $22.00 for 5 quarts. Mixed with 5 quarts of 0W40, new oil cost me less than $50. 5W30 or 10W30 is not sufficient per the boys at Porsche.

[c70Pete]

Our Walmart in Arizona carries Mobil 1 15W50 racing oil, which nobody buys, so it was on sale for $22.00 for 5 quarts. Mixed with 5 quarts of 0W40, new oil cost me less than $50. 5W30 or 10W30 is not sufficient per the boys at Porsche.

why do you mix?... is it ok to mix?

[70Sixter]

Thanks for your posts. Correct me if Im wrong....the first number is based on how cold it gets and the second on how hot it gets? Here in California it doesnt ever get in the negatives or even lower than 20F during the winter and during the sumer heats it could get over 100F but around this time getting close to fall and all its floating around 85F but usually lower. So if living somewhere alot colder and not getting as hot 0w40 makes sense.

So with that said and done wouldnt 10w30 or 10w40 should be fine???

Can some clarify or explain why I still should use something lower. I just need clarifications.

Thanks again.

Yes, the first number is basically protection at start-up and the second is at operating temp. The more viscosity improvers required to achieve the rated numbers, the less base available for lubrication.

No 30 weights are approved, and it is a terrible choice for protection of an M96 at operating temp. The are several approved 0W and 5W-40s and one 50 IIRC. The TSB is available here on this site for contributing members. Do not go by the owner's manual as oils are "reformulated" and approvals change. Even the TSB approvals have an expiration date listed.

I have come to believe after much research and debate in this forum and others that 0W is not a good choice for most M96s unless you live near the Arctic Circle. You want a minimum API rating of SL, altho SH or SJ are better. European ratings of A3/B3 are also signs of good quality oil.

SM and CJ oils are not considered by some experts to be adequate for Porsches, altho there are SMs on the approved list. Motul 8100 X-Cess is approved and meets minimum SL/CF requirement.

By the way, Mobil 1 5W-40 is approved, but not available in the US to my knowledge.

ZDDP is very important as jperquin said, but you do not want to add it, it needs to be in the oil's formulation. Some say it can damage cats, which is one reason why the ZDDP levels have gone down in many oils in recent years.

IMO opinion there are better oils available that are not on the Porsche list if you are off warranty. Some are very expensive - like my Motul 300V 5W-40.

[c70Pete]

IMO opinion there are better oils available that are not on the Porsche list if you are off warranty. Some are very expensive - like my Motul 300V 5W-40.

is the 300v 5W-40 appropriate for tracking and lapping days? why would not the M1 5W50 be a better choice for tracking since it has a higher viscosity?

[70Sixter]

is the 300v 5W-40 appropriate for tracking and lapping days? why would not the M1 5W50 be a better choice for tracking since it has a higher viscosity?

I do not know. I'd ask Charles Navarro at LN Engineering. I never talked tracking my Box with him. Racing oils might be more appropriate with a post track switch back to a street oil.

I know he likes Brad Penn (previously Kendall) 20W-50 for Porsche air cooleds street or track.

[phillipj]

Mobil says it is okay to mix on their website. Whether Porsche says it's okay I don't know :P

[c70Pete]

Mobil says it is okay to mix on their website. Whether Porsche says it's okay I don't know :P

well if you would do a mix... then say 5 quarts 15W50 with their new "extended protection" 5W30 (say 4 quarts)... would be best? because of the extra supersyn? I really don't know about this as the 30 type oil would boil much sooner than the 50 weight... how does that affect engine at high operating temps?

[Falcon900EX]

So it has to be a XXw40?

Edited November 14, 2009 by Falcon900EX

[wross996TT]

So it has to be a XXw40?

These oil threads go on forever...read here if you want more info Bob the Oil Guy. In particular search for posts by Doug Hillary (also on rennlist) as he has done extensive analysis of oils used in European cars. The first number is the viscosity when the oil is cold...you want it to flow when the oil is cold...therefore go 0 or 5...the second is when the oil is hot...40, or 50 are recommended.

[1999Porsche911]

Just so people do not continue to fall for gimick advertising of viscosity, the viscosity of oil is determined by the amount of flow caused by gravity. What you are not told, is that the flow of a 0W40 oil and a 15W50 oil under pressure such as in your engine, allows the oil to reach all engine components in the same amount of time, all the way down to around 0F. For hot oil visosity, you are also not told that the most important rating is the dynamic or absolute viscosity, which determines how much the oil will shear while under pressure. Look for higher HTHS Viscosity in an oil. Mobil 0W40 has a HTHS Viscosity of 3.7 and 15W50 has one of 4.5. The W (winter) rating of the oil effects the shear rating in many cases. For example, Mobil's 10W40 has a HTHS Viscosity of 4.06 which is 10% higher than their 0W40 oil, even tho they are both 40 weight oils.

[achillies]

The latest TSB says that oils that are Porsche approved and of the same specifications can be mixed but warns that each oil brand can have different formulations, etc. It reads like they are talking about during and oil change....it dies say that top offs should be the same as what was in the cr.