I've attached the speed diagnostics oil report from my latest oil change. I put 0-50 Mobil 1 Supercar in and it still failed viscosity. The oil wouldn't even pass 40wt viscosity but the results are at least closer. Starting with the first test, these tests were from a new engine. Original engine failed at about 15000 miles. Ignore the mileage numbers I started keeping track of mileage on the new engine but gave up doing that and just went with odometer mileage this time. Interesting how the numbers have improved with mileage. The oil was not in range for a 50wt oil but, the oil fell in the range for a 40wt.

 

Thanks for sharing. This is why I exclusively run 5w50 in my car.

 

In the case of 0W-40, your samples tested in the middle to upper range for a 30 wt oil. Your 5W-50 tested in the middle range for a 40 wt oil.

The sample mileage is the actual mileage between oil changes? Both of these Supercar oils shear down in viscosity quickly and then level off. In the case of the 5W-50, new oil out of the bottle tests right at the very bottom of the range for a 50 wt oil. In my last analysis, at 2200 miles the viscosity was solidly in the 40 wt range. The car is a 2023 Z06.

 

Thanks for the info. Looks like I'll stick to 3,000 miles per change.

 

Is the assumption here that this a bad thing? Unknown to the engineers?

 

Unknown what the engineers think. Mobil 1 Supercar 5w50 is approved on the dexos list. I live in the south and its hot in the summer on track the car will run 230 water temp all the time. The 50wt oil that degrades down into the 40wt range is better than a 40wt that downgrades to a 30wt. Track prep used to say "change oil out to 15W 50" so the use of a 50 wt isn't new. If I wasnt tracking the car I'd use the 0w 40 and not worry about it.

 

My big question would be does using other than 0W-40 void the warranty how does GM look at this I do not track my car but live in a hot climate state?

 

Thanks, three things:
1st we had an oil company formulator who said when it 1st came out he reserved judgment as "viscosity improvers" reduce their effectiveness with miles driven

2nd had a friend who worked at EXXON as their Chief Welding Engineer. Recall he told me they supplied a bottler viscosity improver in truck loads. They filled bottled of STP. They shipped directly to retailers STP was a great marking program but no facility! Love their "Can't Hold A Screw Drive By The Tip Coated with STP.

3rd I started using Mobil 1 in 1974 when it was hard to get and very expensive. The Datsun service rep told be to put it in my two large Hitachi SU variable venturi Carb dash pots! The 1974 260Z was as all cars that year subject to new EPA rules. It was before CATs and mine had an air pump putting air aimed at the exhaust valve in the manifold, they added coolant to the intake manifold to better atomize the lean fuel mixture etc. (Heck the 1974 Vette small block only put out ~200 hp. To get 275 hp had to opt for the 454 big Block!) It was doing what he called "Porpoising" when acceleration rapidly after it warmed up. The Dashpot Oil was losing viscosity and the large piston fluctuating excessively up and down. He said a new oil they were selling to the military in Alaska has a very wide viscosity range It was a man made POA OIL (Polyalphaolefin, a premium, lab-synthesized base fluid used in high-performance synthetic lubricants.) It worked and the 260Z that was not doing what F1 cars were a few years ago. After reading the oil details and very high temperature capability details I started using in in my modified Corvair engine where the oil could get to 325F per the temp gauge I installed. There was a scum in the oil fill pipe soon after changing oil. It was breaking down. Mobil 1, labeled Synthetic, cleared that up!

But Mobil lost a suite to Castrol who was calling their essentially regular oil "Synthetic" saying it was more "highly refined." The article below (few you'll find) said that essentially "dino" oil cost half what POA oil did to produce and Mobil changed! Had to. The price did cut in half. By then no more Corvair but have used Mobil 1 since!

SIDEBAR
Great read in Car & Driver by Patrick Bedard when Mobil lost the suit. Won't find many car mags discussing because oil companies are advertisers.

He starts with "Now that the meaning of "is" has gotten so slippery you need to grab it with both hands, we'd better keep an eye on longer words, too." Referring to the Clinton Lewinsky affair!
https://www.caranddriver.com/feature...antics-column/