I know this may of been said before BUT:

I'm in the middle of looking at engine oils to run in my 86 Trans Am. It's a long story, but see here in Australia, we tend to run heavier oils then in the USA for some reason.

I have spent a fair bit of time asking companies like Comp, Crane and Crower what oil they recommend for the typical street TPI SBC and most have come back saying Mineral based 20w 50's.

When I have mentioned this to people in the States they all think I'm telling stories, and are suggesting to run oils like full synthetic 5w 30's.

To me that just seems a bit to thin when even Australian oil companies are pushing 20w 50's as oils purpose made push rod style V8 engines.

I was just wondering what the general thoughts are on what style of oil is best to run in these TPI SBC's.

Thanks so much.
Francis.

 

Assuming a 5W-30 synthetic down under is the same as an SAE 5W-30 synthetic here in the States, go with the 5W-30 synthetic.

 

wow that's thin!



We here are using oils like that in the latest model little 4 Cyl cars. Dealers are also using it in GM V8's and Ford 5.4's and even they had issues with using oil.

See Pennzoil (USA) even have a 20w 50 GT Performance and the writing on the back even makes some sort of reference to it being suited to push rod style American V8's pre 90's.

If I was to use a 5w 30 in a say a 1971 GTHO 351 Ford Falcon or 1971 350 Holden Monaro I believe it would use a heap oil and I don't think you would find any owners even with original low kms models using anything less then 15w 40 and most going the 20w 50's

 

yea, you can run super thick oil like that on a motor that's SUPER worn out. My dad used to tell me stories about people throwing in gear oil in the crank case to keep the howl down, while trying to sell a ratbagged car.

That tpi car you refer to, is still a roller motor, like all new cars, and those GM V-8's (new ones) are still mostly pushrods. So not a lot has changed.

20W-50 is a decent racing oil, or good for a realllly worn out motor, but 5/10W30 is just fine for your use.

A rebuilt motor in that old ford falcon would take 10w30 quite nicely.

 

on cold start up thick oils take longer to get to everything.
the thinner oils get there much quicker.
if it takes 10 seconds after startup for the last set of rod bearing to see oil pressure, they are getting hammered from lack of lubrication.

years ago i use to run 20w50 in the summer, after a few thousand miles i would start getting cold startup rod knock & i would need to replace the main & rod bearings to stop it. on my last 3 motors i have run nothing but 10w30 year round with no problems.
the motor in my car right now went 92,000 miles on 10w30, i have put an additional 80,000 on it with 10w30 with no problems.
a side benefit of running a thinner oil is a little more power to the ground.

 

Wow, the only reason i would run something that thick is if the motor was ready to be thrown out and ambient temps were 200*c!


10w30 should be good for it, thats all i run!

 

I would use a mineral 10w30 If you are worried about using oil. From my experience synthetics burn and leak more than conventional oils, but thats in my experience.

 

5W-30 was the recommended viscosity for our cars from the factory. If you live in an area that doesn't get that cold, 10W-30 is just as good.

Pushrod style pre-90's V8 isn't the real issue here. Flat-tappet vs. roller lifter is the dividing line. Pennzoil recommends the 20W-50 because it has anti-wear additives that are important for flat-tappet engines but have been removed from GF-4 rated oils for emissions reasons for the latest engines, which use roller lifters.

Only the '85 & '86 3rd gen TPI's had flat tappets, so if yours is the more common '87-'92, you have roller lifters and the anti-wear additives aren't as important. Personally, I use an AMSOIL 5W-30 diesel synthetic (also rated for gasoline engines) which has those additives in it for my two flat-tappet vehicles. One is raced, the other is a tow vehicle, so these are not light-duty applications. The 5W-30 does just fine in them.

If you think 5W-30 sounds "thin", many US OEMs are specifying 5W-20 for their new fuel-efficient, low-emissions engines these days.

 

I run Valvoline VR1 20W-50 in my 88 Formula due to the milage of my engine, about 160K. 10W-40 was a little thin and my oil press was kinda low.