The Stovebolt Site Forums The Shop Area The HiPo Shop Is semi synthetic oil OK in my SBC?

I have a 350 small block of 1981 vintage in my AD,I'm finally getting round to changing the oil,the stuff in it was only intended as a flush through as it had been sitting a while.
I have never been inside the engine as it doesn't smoke,knock or rattle and makes good oil pressure 50psi cold 20 hot so it didn't make financial sense to me to rebuild it.(If it ain't broke don't fix it")
Long story short that was over a 1000 miles ago!

I'm having a heck of a job sourcing a standard mineral oil locally,the Corvette manual calls for a 5w-30 or a 10w-30,I can only get these in a semi synthetic round these parts,will this be OK?

The only caveat I have seen on synthetics is to avoid them with new camshafts during break-in. Other than that, they are fine. I run synthetics in every engine I own, including my lawn equipment. They take the heat of heavy duty operation better than standard oils. My autos have 102,000 and 75,000 miles now.

On a higher mileage motor synthetic tends to leak past the old seals more than std non-synthetic, at least that's been my experience.

I went away from Mobil One and back to Valvoline VR-1 partly due to this, also due to cost. I just don't drive enough miles to justify the longer mileage oil change intervals that the synthetic provides too.

Hope that helps,

John

The leakage issue supposedly occurred when synthetics were new on the market. Now they have additives in the synthetic oil to help swell the seals and gaskets and prevent leakage.

Interesting. In my case I switched from Mobil One 15W50 to Valvoline VR1 20W50 Fall 2011 on my 3 sbc powered vehicles and noticed less leakage on all three?
I have cardboard under all 3 vehicles in the garage, the leakiest of the bunch is my '65 C10

Thanks for the input gents,I've heard about the additives to swell the seals so I guess i'll go ahead.

I had a little oil leak on the LH side but it was actually down to a slightly loose oil filter...
I drained it yesterday and the plug was free from any goop or swarf so hopefully all is well inside

The oil was pretty black on account of a badly adjusted choke,it was running super rich.

Not good when gas here is over $10 a gallon....