# Oil type GTO 67



## Viking13 (May 29, 2018)

Hi gents

Anyone who knows original spec for engine oil, transmission and rear axle?
It´s orginal matching numbers car with 400 (335 hp), TH400 and for the moment i cant remember which rear axle.

What type do you use?
10W40?
20W50?
High Zinc?

Best Regards 
Marcus


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## PontiacJim (Dec 29, 2012)

Viking13 said:


> Hi gents
> 
> Anyone who knows original spec for engine oil, transmission and rear axle?
> It´s orginal matching numbers car with 400 (335 hp), TH400 and for the moment i cant remember which rear axle.
> ...


Factory recommended 20W oil above freezing or 10W-30 as an alternate. Automatic trans uses Dextron fluid. Manual trans - SAE80 weight. Rear axle - SAE80 weight, but requires additive #1050081 .

But, asking what oil is a loaded question. If the engine is stock, ie flat tappet camshaft, you need an oil with Zinc such as Brad Penn or Joe Gibbs or you can get a zinc additive. Some use the synthetic blends and say they are OK, but I have never used them.

Oil weight depends on outside temps, and engine wear as well. I would use 10W-30 as a minimum and might even opt for 10W-40 if it has miles on it and for hotter summer weather. 20W-50 is too thick unless you have opened up the clearances on your rod & main bearings - ala racing engine, and have the oil pump and aftermarket pump shaft to turn the thicker oil.


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## geeteeohguy (Feb 2, 2008)

What Jim said! I run 10/30 or 15/40 Rotella in all my old cars...not problems in many years and miles.


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