GM Specs my ass

[Sarge]

I purchased a new Silverado a couple of weeks ago. Have 500 miles on it now and time for all new fluids/filters etc. This dadgum GM spec 9986115 for the rear end gear oil threw me for a bit. So I emailed Mobil/Royal Purple/Amsoil for info on that spec. I also called the GM Regional Rep.....here is what i got....
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From Royal Purple......
Royal Purple's MaxGear 75W90 meets and exceeds any performance requirements for this application and if our product was the direct cause of a denied warranty, Royal Purple Inc carries liability insurance that would apply in the event that GM denied you warranty service solely on the use of our aftermarket product.

There is not an industry performance specification for the GM #9986115, it is a purchasing specification set by GM.

Heck, GM created a specification for a 23 oz packaging for a SAE 75W90 oil with a specific part number because that we the specified fill amount!

Specification sometimes are performance related - in this case - it is a separate part number to indicate that the limited slip friction modifier is already included in the product where previously, GM had specified separate gear oils and then an additive concentrate of the friction modifier.
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From Mobil1
No, you must procure this product at your local dealer.
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From Amsoil

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From the GM Regional Rep
The spec is for friction modifier to be included in the oil versus two separate bottles. So basically it is a packaging/purchasing spec only. As long as your choice meets API GL5 specs and has the friction modifier your good to go.
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So it is a purchasing/packaging spec and has nothing to do with the formula or additives at all. Now the punch line. GM is selling that shit for $25.00 per quart!!!!!!!!!!!!!
What a bunch of dickheads!
Sarge><GM

[310stanger]

so what exactly was the problem? lol sarge you change gear oil that early?

[Sarge]

Hell yes. All fluids except Brake/Steering comes out and real fluids and filters go in.
I drive the shit out of em for 500 miles. Floor it from every stop light and highway on ramps are my personal drag strip. Do that for the first 500 miles and then change the trannie/rear end/engine oil and filters....then drive "normal"...all my cars have always lasted very well and have excellent performance from doing this.

[Zapper2003]

I've always heard, 'break em in like you plan to drive em'.

[310stanger]

Hell yes. All fluids except Brake/Steering comes out and real fluids and filters go in.
I drive the shit out of em for 500 miles. Floor it from every stop light and highway on ramps are my personal drag strip. Do that for the first 500 miles and then change the trannie/rear end/engine oil and filters....then drive "normal"...all my cars have always lasted very well and have excellent performance from doing this.

i see. and now i know what you were getting at with the 75w90 after reading it again. That oil is basically an oil creatively "made up" by GM to sell for an expensive price for people to think they need it. Use the 75w140 with the friction modifier and you're good to go

[joerockhead]

I drive mine that way ALL the time.

I thought the light at the On Ramp was a perfect practice for Drag racing!

[94z28l]

I drive mine that way ALL the time.

I thought the light at the On Ramp was a perfect practice for Drag racing!

me too, finally got excited when i saw tax dollars doin me some good

[Rickys S/C Z28]

hell yes drivem hard and leavem wet!!!!!!!

[Pulse Red GTO]

That's the way I always broke in my performance car's I bought!! When I picked up my 02 TA WS6 at the dealer, I had it redlined doing a burnout leaving the dealership!!! That baby only had 105 miles on it! Also in my 04 GTO, did the same thing!! The service manager always told me the best way to break it in was the way you were going to drive it!!! I normally didn't change the oil to synthetic till around 2k miles though