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Discussion Starter · #1 ·
Maybe I missed this somewhere but I will ask anyway. GM recommends a 15w-50 oil for "racing" and "performance" driving. I can't find a 15w-50 dexos approved oil. Anyone? Mobile 1 15w-50 is not Dexos approved.
 

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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.
 

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As you see from GM they recommend Mobil 1 15W50 for the C7 and track use

ExxonMobil today announced a new lubricants technology agreement with General Motors (GM) for the Chevrolet Corvette.

As part of the relationship, Chevrolet has chosen Mobil 1™ motor oil as factory fill for the highly anticipated 2015 Corvette Z06 and the 2014 Corvette Stingray with the Z51 Performance Package.

Building on a 21-year lubricants relationship with ExxonMobil, Chevrolet also named Mobil 1 5W-30, which meets or exceeds GM dexos1® specifications, as the recommended service fill for all Corvette models.

In addition, for on-track and high-performance applications,
Chevrolet is recommending owners use Mobil 1 15W-50 to ensure full engine protection and optimal engine efficiency*.


“It is a testament to ExxonMobil’s commitment to advanced lubricant technology that Chevrolet has chosen Mobil 1 synthetic motor oil for the high-performance Corvette engines,” said David Tsurusaki, strategic global alliance manager, ExxonMobil Fuels & Lubricants.

“As the Corvette Stingray hits roads around the world, we want Corvette owners to know that Mobil 1 motor oil is specifically designed to meet their high-performance demands and will help keep their engines running like new.”

With a factory-fill relationship that began in 1993, ExxonMobil has a legacy of helping Corvette engines perform at their maximum with Mobil 1 lubricant technology.
Mobil 1 motor oils are designed at the molecular level and enhanced with a proprietary additive system to provide outstanding protection against wear, high heat, cold weather and sludge buildup.

In addition to select production Corvettes, Mobil 1 lubricants drive efficiency and power for Corvette Racing’s C7.R in the TUDOR United SportsCar Championship.
With Mobil 1 lubrication technology, the Corvette team competes in some of the most demanding endurance races in the world including the 24 Hours of Le Mans, Rolex 24 at Daytona and the Mobil 1 Twelve Hours of Sebring.
 

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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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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 ???
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.
 

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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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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?
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.
 

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I know that there is no such thing as break in oil these days...
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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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
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.
 

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Discussion Starter · #10 ·
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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Dexos approved is mainly for marketing....and even w/out break-in oil from the factory, don't leave it in more than 1000 miles with the break-in debris, etc. circulating.

For us, we drain the factory fill, then fill w/a good conventional (Shell Rottella my choice) and then do the hard acceleration/deceleration break-in. After that full syn only.

Here are some pictures to show what occurs during the first few hundred miles:

Below is a fresh cross-hatch hone ready to assemble. Note there is no glaze, and the abrasive nature of the hone finish is what will "seat" or wear the rings into the shape of the cylinder wall for proper sealing:


Now look at this example of a GM engine with excess oil consumption. Owner followed the break-in in the owners manual and babied it. This is at 12k miles, and has used a qt every 2k miles since new.

Look closely at the cross hatch still plainly visible, (should be almost gone if the rings seated properly) and a mirror like glaze has set in and covered it so no seating can occur...in fact, after 3-500 miles the window has passed and there is nothing you can do but disassemble and re-cut, replace rings, and break in properly (hard) to eliminate the consumption issue (what were doing with this engine):



Hope this helps!
 

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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.
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.
 
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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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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?
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.
 

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Dexos approved is mainly for marketing.

Where did you get that ?

Far from it

Due to E10 and last year E15 gas approved GM wanted a top tier gas and engine oil that would assure internals were getting cleaned

Add the issues with GM now with powertrains with DOD, DI and VCT along with supercharged, turbocharged and increased EPA fuel mileage rules GM needed
engine oils better then some snakeoil vendor just saying "meets GM requirements"

Pre dexos1 and dexos2 nameplates went by SAE/API and oil makers who never even bother getting tested by SAE made false marketing claims that their oils "exceeded" that standard so GM wanted to assure no such claim and makes it clear a vendors oils must be GM tested.

It came down to the norm of "standards" where Japan and Europe attempted to drive a new American SAE standard that was biased to those countries oil makeup as both then wanted American vendors to have to pay those 2 countries a fee.

GM said the hell with it and came up with American dexos1 and Europe needs in dexos2

Oil today has to have a makeup to assure nameplates like GM can do 100,000 mile powertrain warranty so a oil design for today's engines had to come about.
 

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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?
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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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
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.
 

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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.

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.
 

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All engines operate at higher internal temperature when worked harder. And all oils, including synthetic oils, fall in viscosity as temperatures rise. Thus, the 15-50 is better suited to conditions where the engine is being driven hard, and the normal 5-30 oil is better suited to normal, lighter duty conditions. Each oil has its application, and each should lubricate better under the condition it is specified for. Moreover, with all of the pressure on car manufacturers to improve fuel economy, a lesser viscosity oil has less "pumping loss", which requires more fuel to overcome.
 

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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.
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.
 
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