I read all these good points with great interest. Contrary to what one can intuitively expect, the only oil from the group that doesn't meet GM's recommendations seems to have the edge here, while the one that's supposed to provide better protection when cold starting an engine appears to be at a disadvantage.

Wanting to find more info on this subject, I went to "Bob Is The Oil Guy" website and found an interesting paper by Dr. Ali E. Haas (AE Haas): Motor Oil University. It is divided in chapters, each touching a different aspect, to facilitate reading.

To my surprise, Chapter #7: Motor Oil 107 (bottom of the page) doesn't agree with the ZDDP concerns expressed above:
The conclusions in Chapter #10: Motor Oil 201 (bottom of the page), which are well presented and supported along the document, do not agree either with what seems to be the general consensus here. According to this paper, the most appropriate oil (from this group of 4 oils) for our application would be Mobil1 Advanced Fuel Economy 0W30:
What do you guys think?

 

YUP, , only I live in Callyforny.

 

I am going to continue using #2 and let the DIC tell me when to change OIL.
FRED

 

Option #2.

 

ZRod 10w30 and changed along with oil filter every other track event=3 oil and filter changes a year on about 6000 miles on the clock

 

Why this comes up eludes me, but for any of us that haven't used search, my 2003 came from the factory with Mibil-1 5W/30 in it and I just bought 7 quarts today for 39.42 at wally s place. If's OK for GM, Porsche and Mercedes Benz AMG division then it sure is fine by me. I don't want to re-engineer something General Motors spend a lot of money and time on a already answered question. And Amsoil is the factory fill on anything.

 

I'm with FRED.

 

Good ol' #2

 

I'm planning on changing the oil this weeked. My car is not a daily driver and it never gets to the point where the DIC recommends a change, so I change the oil once a year.

I have always used "Option 2": Mobil1 - 5W30, which after all is what it had from the factory, but after reading the 10 chapters of the Motor Oil University paper in Bob Is The Oil Guy website, I decided to try Mobil1 - 0W30.

The author makes a solid case, presenting data to support his point, and besides, Mobil1 - 0W30 follows GM4718M.

 

Just keep in mind that Mobil is not General Motors. I would consult my owners manual before changing to an oil that isn't recommended specifically BY GM.

 

I was amazed by the 'Bob the oil guy' assumption that Mobil-1 is a poor motor oil in some ways. Every Corvette including the LS9 comes from Bowling Green, Ky with it in it's oil system and both Porsche and Mercedes Benz AMG divisions use Mobil-1. They use it unconditionally even though Castrol Edge is available and is a European petroleum company and is owned by BP, yeah the same guys who dumped 25 million gallons of crude into the Gulf of Mexico. But . . .

 

that SL and SM are different. SM and SN are the newer modern oils but SL allows a higher % of phos/zinc in a 30w. for the sporty driver i would say the mobil1 high mile is the way to go, it's also SL rated. yes it doesn't have the gm seal of approval but the reason WHY is just that. the higher zinc/phos which is great for anti wear, also is a concern to GM because of the cats. oils like redline and amsoil would be track day oils mostly due to cost in my eyes but man, you won't beat their shear stability or higher zinc/phos levels.

oh, and the advanced fuel economy oils have the lowest zinc/phos of all

 

And He said, "Let there be light." And there was light. And it was good.

 

Your question is a hard one with many variables. Probably no one right answer. The Mobil 1 and Mobil 1 Extended Performance both meet the OE requirement for GM 4718M and the new GM dexos1 spec - doesn't mean they are the "best" oil. The difference between these two is that the Extended Performance will have more calcium as a detergent/dispersant to help combat Total Base Number drop due to acidic engine cumbustion byproducts that build up in the oil over time. If you change the oil at historic oil change intervals (e.g. something around 3k or per the Oil Life Monitor), probably not worth paying for the Extended Performance oil.

The Advance Fuel Economy oil is similar to the base Mobil 1, but gets better fuel economy as it has a lower viscosity. I would discount it.

The High Mileage is, in my opinion, the best choice. The owner's manual requires an oil that meets current API specs. At the time the C5 was designed, the API specs allowed phosphorus, which along with zinc, is a key anti-wear additive to be ~1200 ppm. Over time that has dropped and the current API spec (SN) only allows 800 ppm phosphorus. The reason for this is that phoshorus causes long term "damage" to the cats (e.g. they don't do the job they were intended to do) which violates EPA regulations. Thus the new oils (e.g. Mobil 1, Mobil 1 Extended Performance, and Mobil 1 Advance Fuel Ecomony) all are limited by 800 ppm phosphorus. The HM on the other hand has 1000 ppm phoshorus.

Personally, I'd blow off the OE recommendation for a car out of warranty and buy the better oil, which in my opinion is the High Mileage.

Responding to a comment that the AMSOIL is 2x more than Mobil - that is a misperception. I can't quote pricing online, but can share in a PM for those interested. And, I'm happy to get AMSOIL at dealer wholesale, about 25% below retail, for forum members via the AMSOIL Preferred Customer Program. Drop me a PM if interested.

 

 

Thank you for your very informative reply. This forum is fantastic, but its members and supporting vendors are the ones who truly set it apart!

I have a question. You mentioned that Mobil1 Advanced Fuel Economy is similar to the "regular" Mobil1, but with a lower viscosity, and that it should be disregarded. I would like to know why.

If I understand this correctly, Mobil1-0W30 Advanced Fuel Economy has a lower viscosity than "regular" Mobil1-5W30 at ambient temperature, but at normal engine operating temperature they have both the same characteristics, that is, both of them have grade 30's viscosity. Therefore, at normal engine operating temperature both grades should provide the same level of lubrication, while when cold starting an engine the 0W30 is supposed to provide better oil flow/lubrication by being less viscous.

By this analysis, 0W30 seems to be the one to beat! On the other hand, Mobil complicates thing further more by making the zinc and phosphor content of the 0W30 lower than the 5W30 (750/650 vs 900/800)!!! Go figure... So, which one comes on top?

I understand what you said about 97-04 API specs vs current API specs and the fact that Mobil1-5W30 High Mileage (with its Zn/P content of 1100/1000 respectively) is the one that most closely matches the recommended API levels when the C5 was designed. My concern here is that the High Mileage formulation says it contains extra cleaning additives and seal conditioners. Would those be OK for a "low mileage engine", or could they be harmful?

Thanks again for taking the time to participate in this thread

 

M1 0w-40

 

Folks over on the c6 section are very high on this. Nothing but good reports.

 

It's a great oil.

You have to get past the "The handbook says 5w-30" mentality to really pick the oil right for you. Nothing wrong with going with the handbook, it still a good general statement. But one really has to look at your driving/usage habits, climate, and assess an oil based on it's specs before passing judgement.

The 0W-40's Viscosities at 40c/100c (which place it around a light 40w) are fantastic, and after the VII shear down it starts to perform like a heavy 30w. With an outstanding HTHS of 3.8, it's one of the highest among the heavy 30/light40 weight oils I've looked at. The additive package with a high TBN and high zinc/phos is great. Plus the price is right.

My buddy is actually running a blend of M1 0w-40 and 15w-50 in his Porsche 911.

 

Just changed the oil in my WS6's LS6 with the Mobil 1 5w30 extended performance. It's the first time I've used it and it was a special from Advance Auto Parts 5 qts+Mobil 1 exp filter $30.99. I put about 5k on my C5 since it's last change with the regualar mobil 1 and right now it's showing 29% left, another 1k and I'm going to change it with the extended performance stuff.