The Stovebolt Site Forums The Parking Lot '60-'66 Trucks Tires and oil

Just picked up a '65 GMC 1/2 ton with a V-6 and 3 speed on the column. A very nice, original(but not perfect) truck. Looking for oil recommendations for the engine, trans and rear end. The owners manual is showing 30 weight for the engine and if I'm looking at it right, 80 weight for the transmission and rear end. Is that what other people are using or is there something better? While I will keep the truck original, I would like to change the tires over to radials. The manual has a 7.75-15 or 8.15-15. Bias of course. Converting to P-metric, I'm guessing somewhere around 205-15/75R15. Appreciate any help.

Start here.

http://6066gmcguy.com/gmcv6a.html

I have a 305 and use Shell Rotella straight 30 weight, designed for diesels I think but was turned onto it by another V-6'er

You'll find that a 205/75/15 will be too small. A 225/75/15 would be closer in diameter and load capacity.

Agree with Bill. I have 215/75/15. 205 would be too small.

Transmission and Rear Axle Lube: GL4 85W90 from Napa

As for oil for your engine, Rotella was a good choice a few years back, not so much anymore. Oil manufacturers are changing their formulas based on changing government standards so what used to work may have changed and not work now. You really need to stay on top of what is actually in the oil every time you buy it. Check out this article, very informative: http://www.hagerty.com/classic-car-...iews/All-Articles/2013/08/07/Classic-Oil

I run Valvoline VR1 in my flat tappet cam motors. Don't turn your back on it 'cause it is for "racing motors".... your flat tappet cam needs ZDDP, and VR1 has it: http://www.valvoline.com/products/brands/racing/racing-motor-oil/6

Hope that helps!

With a stock profile camshaft, the current API grade oil (SN) will be just fine. It only becomes an issue with breaking in a new camshaft, or if you're running a high lift performance cam, with or without high rate valve springs.
That said, I will second the use of VR1, I use it in my '55 235, which has an M4F Howard race cam in it. However, on my S10, with a stock grind flat tappet cam, I use standard Valvoline.

Great, all my questions answered. And very interesting about the oil. There was a national classic car club a person could get high zinc content oil from but can't remember the name of the club. Thanks to all.

Since we are expressing opinions and thoughts here I'd like to add a line or two.
First thing is that engines already "broken in" do not have to have additional ZDDP.
However, the advice of a local engine builder, think re-manufactured engines, SUGGEST that if you are running a flat tappet set up that it "would not hurt" to buy the 12 oz bottle of ZDDP additive and put about 4 ounces to an oil change. While it may not "need it" he suggest it certainly would be worth the money. Since we don't change oil in our old flivers that often it may be something one would consider doing since most of us want to "err" on the safe side.

Just a thought and suggestion I pass on as information.

Yeah that's it, Classic Car Club Of America. Sorry I missed that. Between the crappy gas and everything being remove from the oils, I'm surprised the old girls run at all.

Being a proponent of "Can't hurt / Might help", can you suggest a brand and item for a ZDDP additive?

These two are available at my local Advance Auto Parts:

> Rislone Engine Oil Supplement (11oz) "1996 and older - Add one bottle to crankcase."

> Lucas Oil Products TB Zinc-Plus Engine Break-In Oil Additive (16oz) For break-in, change after 1,000 miles. Add full bottle to crankcase for older cars.

How much to add to crankcase? Alvin's engine rebuilder suggested 4oz. of a 12oz bottle.

Thanks,

- Lonnie

Other than for break in purposes or if a high-lift/high rate valve springs have been installed, those additives are unnecessary. Use a good brand of regular oil. There's an excellent article on oil types, API ratings, and the myths about motor oil in the current issue of Vintage Truck.

Good stuff, Bill. Thanks for sharing.