Is there a dexos approved 15w-50 oil?

You probably won't find any DEXOS certified oil in that viscosity because part of the specification is based on the oil's contribution to fuel consumption. High viscosity oil reduced fuel economy hence no certification. If you are worried about engine protection just use the API certification, that's the one that really measures the oils ability to protect your motor.

Milliwatt Rob said:

As 5w-30 Mobil 1 is factory fill for the z-51, can we conclude that there is no special "break in" oil used? And second, as Mobil 1 is factory fill for the z-51, can we assume the initial free oil changes at the dealer will also be Mobil 1 ???

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Manufacturers haven't used "break in" oil for decades aside from a few cases where Honda added additional moly to some specific engines back in the late 90's so no, there is no special break in oil in any C7.

There is still confusion on Mobil 1 factory fill since the ONLY documentation of that comes from Mobil, not GM (that quoted article above comes from the Exxon/Mobil website). Some dealers will do Mobil 1, some won't and GM has not sent any notices to the dealers regarding Mobil 1 to the dealers that I am aware of. Until they do it's a case by case crap shoot.

Milliwatt Rob said:

I know that there is no such thing as break in oil these days, but I keep on seeing references to people wanting to get the 'break in oil" out of their engines before the first GM recommended oil change. Do they know?

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Old people use old phrases........ Most simply consider the oil used during the engine break in as "break in oil", not that it is any different than the oil that will replace it but that it has particulates in it that come from the break in process.

Mobius said:

Honda still uses a specifically formulated break-in oil, and in my experience it's very effective (I'm the original owner or a 2005 Civic that just passed-through 475,000 miles).

"Your Honda engine was delivered with an oil that is specially formulated for new engines that have not yet developed their "natural" wear patterns and may contain minute particles from the manufacturing process.

American Honda strongly recommends this special oil be left in the engine long enough for these wear patterns to develop, usually until the first maintenance interval specified in your Owner's Manual, based on your specific driving conditions." Frequently Asked Questions | FAQ | Honda Owners Site

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Hmm, i wasn't aware they were still doing this. They would be the last I believe, it's not a standard practice, certainly not by GM.

Sunrise said:

SO BACK TO SUBJECT....GM on one hand tells you to use dexos approved oil and then says but if racing or performance driving recommends a 15w-50 oil which is not a dexos approved oil. Just seems silly to me to make a big deal about the "Dexos" approved but then turn right around and recommend a non dexos approved oil. I guess the viscosity any 15w-50 oil is such that it is safe regardless of dexos? Why not run 15w-50 all the time if it's so good it doesn't need dexos approval? Thanks in advance for your answers to my question.

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It's not silly from either a marketing or an engineering standpoint. The DEXOS spec oil provides the combination of protection, efficiency and driveability the engine is designed for. The higher viscosity "racing" oil provides an added level of protection the motor needs under the higher stress use. To provide that higher level of protection it gives up varying degrees of protection, efficiency and driveability under "normal" street driving conditions.

Just because the 15W-50 protects better at racing stress DOES NOT mean it protects better under normal stress. The idea that, "If a little is good more is better" just doesn't apply here. Use the oil (and brakes, tires, etc.) that best suit the driving mode because there's is no such thing as "one size fits all" with any of these consumables.

thrilled said:

I believe if you live in A hot weather area then I believe that A 50W oil would be good for the cylinders and rings.I do believe that A low weight oil in hot weather isn't good for the engine.I've always believed this.Am I wrong?

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Not to be mean but yes, you are wrong. Ambient air temperature is irrelevant as long as the engine can manage it's internal heat. It's the stress of high performance driving and / or racing that raises the internal temperature of the engine and oil, not ambient air temp.

J.R said:

Too thin of a oil and in hot weather, engine and track use becomes blowby, through PCV and into the intake where reverb of exhaust can send the oil fumes to aircleaner.
Thin oil flows quicker so it cools down better and gets a bit better MPG

Thicker weight flows slower so it retains more heat, though it reduces blowby and of course bit less MPG

For racing I have always mixed 5W30 and 15W50 Synthetic 50/50 ratio to get like a 10W40 and at races where powertrain is maintained at high RPM, MPH and engine loads like Open Road Racing the thicker oil does a much better job, less oil and blowby issues

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That's all well and good but he never mentioned track use.

Under normal driving conditions the cooling systems maintain the internal temperatures with a certain range regardless the ambient air temp so what you do racing has no bearing on street use.

Oh, and mixing engineered oils to get a target viscosity ratio simply doesn't work the way you describe and in some cases the blend of incompatible additive packages can cause far more harm than good.

J.R said:

Mobil 1 engineering for GM racing themselves told me of the mixing and it does work and the lack of oil use and blowby shows it and not saying to mix brands but same Synthetic Mobil I

If a Corvette is driven on the street as it was designed ( bouncing rev limter, 100% engine loads. etc) for, the thicker grade works as well as if track use.
Under "normal" street driving if means sticking around 2,000 RPMs is one thing but higher loads, higher oil pressure, more flow, more oil cooling and not about outside temp but overall engine/bay temps.

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You didn't mention you were blending the same base stock, that does make a difference.

I don't know where you live but there aren't that many places where you can legally, and for that matter safely drive a C7 bouncing off the rev limiter, 100% engine loads, etc. for more than a few seconds at a time vs. minutes that you would do it on a track during a normal HPDE event, where each session is routinely 20-30 minutes.

Bottom line, very very few people have the opportunity or ability to stress the LT1 on the street to the point where you need any more than the factory spec 5w-30 oil. If you happen to be one who does then you hardly need someone on an Internet forum telling you what oil to use, you should have that knowledge already or know people who do.

Sunrise,

I suggest you take some of that new found disposable income and invest in some track instruction and track time. Once you have actually experienced high performance driving you will understand.

Have fun and don't kill yourself.

Sunrise said:

Yes, would like to experience that. Maybe at the new track being built in Bowling Green?

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ABSOLUTELY! You should at least take advantage of the discounted Ron Fellows driving school in Nevada. Once you've had the chance to track the car with expert instruction it changes the way you approach driving forever. It a true "ah ha" moment.

BTW, I never meant to denigrate you. It may have come off that way and I apologize. I was lucky enough to be exposed to a race track at a young age so I never felt the need to street race. I forget not everyone has had that opportunity.