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2005 996 C4S. Getting ready to do spring oil change. Plan on using Mobil 1. Question is what viscosity should I put in for Nebraska spring, summer and fall. Do not drive in winter so below -13f is not an issue. Owners manual says "above -13f 0w-40, 5w-40, 5w-50". I used 0w-40 last summer and oil pressure was very good. Street driven only by an old guy(me)!

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OK...my bad! Did a search after posting this question. Saw a similar post from October 2014. Based on that think I'll go with 5w-40 this year. Any new thoughts would be appreciated.

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OK...my bad! Did a search after posting this question. Saw a similar post from October 2014. Based on that think I'll go with 5w-40 this year. Any new thoughts would be appreciated.

 

Instead of the M1, take a good look at Joe Gibbs DT 40, which is an excellent year round oil for these cars.  Very high in ZDDP, it demonstrates excellent film strength and resistance to high temp/high shear conditions.

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Don't mess with Joe Gibbs DT40. JFP in PA failed to tell you in the above post that you should first flush the engine with BR30 due to cross pollination and the fact that the DT40 fights with the Mobil additive package.

 

Use Mobil 5W50. It is Porsche A40 approved. Much better oil than Mobil 0W40. On sale right now at Napa for $5.99 quart plus you can use the current Mobil rebate for another $12 off per case.

 

This is the oil I've been using for years in my 987 Boxster and 991 Carrera S PowerKit. My UOA's show better results compared to DT40.

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From JFP in PA:

 

"Instead of the M1, take a good look at Joe Gibbs DT 40, which is an excellent year round oil for these cars.  Very high in ZDDP, it demonstrates excellent film strength and resistance to high temp/high shear conditions."

 

DT40 has no higher ZDDP than Mobil 0W40. Both are right at 1,000/1,100 PPM. To get the full effect of DT40 users should first flush the engine with BR30 for about 200 miles. FYI.

Edited by White987S

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The very reason I, and others, hate oil technology discussions.

 

As I stated, the Gibbs product is high in ZDDP; and according to its manufacturer, it intends to stay high in ZDDP.  Mobil, like most other oil compounders, have started reducing ZDDP concentrations in some of their products.  While we have not tested every current Mobil product, UOA's have shown signs of these changes as they move to other metal salts to replace the some or all of the ZDDP previously used in their formulations to get mid or low SAPS under ACEA  or API SL, CJ-4, or SM ratings.

 

As for flushing an engine before switching oils, while doing so would aid in removing some the less advantageous additives used in mass produced oils, such as paraffinic compounds, it is not absolutely required.  Yes, the new oil could be diminished slightly by residues from the previously used product, but the level is no where near problematic, as demonstrated by repeated UOA's.  We have converted a lot of engines from other products directly to the DT-40 with absolutely no adverse effects.  So while some engine builders would espouse a flush, not doing so remains a viable option.

 

Lastly, we caution customers against using oils with advertised weights higher than "X"W-40 in VarioCam, and particularly in VarioCam Plus engines, as excessive oil weights have led to problems with the VarioCam system and even VarioCam related CEL's due to these systems sensitivity to oil viscosity.

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While I appreciate everyone's input, I agree with JFP and have already ordered DT40. I only drive the car 1k to 2k during the season so I'll be dumping the DT40 and any contamination from the Mobil 1 soon enough. :thumbup:

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If you ever watch NASCAR, you'll note the Joe Gibbs cars sport Mobil 1 decals.

In any event asking a forum seems dubious when your Porsche owners manual describes oil viscocities and references the A40 specification. There's no better information anywhere.

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"NASCAR and M1" simple sponsorship thing. My owners manual is 11 years old as is my car so oils have changed/improved since then. It also recommends three different weights for summer driving. I was looking for educated/experienced opinions which I have received .

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If you ever watch NASCAR, you'll note the Joe Gibbs cars sport Mobil 1 decals.

 

 

And most of the Porsche GT & Cup cars do as well, and yet many of them do not run Mobil products, but do want the sponsorship $.  When I raced, whosever's spark plugs, oil, tires, coolant, or whatever was paying the most money was on the side of the car; what was in the car was another story.  It is all about money, period.  I remember one event that was being sponsored by a pet food company; I had large dog food decals on both sides of the car, and I don't even own a dog.

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I have been using the DT40 product for the past 2 years in our 1998 base Boxster having switched from the Castrol product since the car now has 119k miles and a recent IMS upgrade while doing the clutch. From a very UN scientific opinion I have noticed smoother initial startups and a 'quieter' engine especially after not having run the car in the non drivable winter months here in central Pa. The local indie we use has also switched over to the DT40 product and it is their oil of choice in most applications.

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