Hey guys, looking to replace the oil in my new project car. Engine is from 1981, but the corvette is a 75. The previous owner never told me what kind of oil he put in, nor the viscosity and if it was synthetic or not. What do you guys recommend? Thanks!
Engine Oil Type
- Thread starter charlesorosz
- Start date
Another Mobil1 user. What condition is the engine? Have you done a leak down test etc. If it is high mileage a good regular oil would suffice whether it be a 30, 40 or 50wt will depend on ring wear. More info on the engine would be helpful.
10 W 30 or 10 W 40 and it takes almost 5 litres of oil unless the pan has been changed. Buy any good quality oil and filter.
As above posters have mentioned more info needed on the engine but I suspect you would be alright with this oil.
As above posters have mentioned more info needed on the engine but I suspect you would be alright with this oil.
More oil information than you'll ever need:
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Passenger Car Motor Oil (PCMO) - Gasoline Vehicles - Bob Is The Oil Guy
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I have always run conventional 10W40 oil in my '75 and added a ZDDP additive. The need for a ZDDP additive or the use of a high zinc content oil like Shell RotellaT 15-40 pertains to engines with flat tappet camshafts. If your engine has a flat tappet camshaft and is stock there's no need for the zinc additive (it won't do any harm so if it makes you feel better go ahead and add it anyway) but if it has been modified with a performance camshaft the zinc additive/high zinc content oil should be used as the pressure on the cam lobe/lifter interface will be significantly greater than stock. There used to be an issue with engine oil leaks given the low viscosity of synthetic oils but I believe that has long since been addressed. Hope this helps.
Temperatures were you live matter as well remember and catalytic converters (if you have one) don’t tolerate zinc additives that are required for flat tappet engines.
I’m guessing improved lubrication leads to reduced friction resulting in reduced heat production rather than the benefit of any ‘coolant’ like effect of circulating oil. Big assumption on my behalf though! 
Yup, I even went back to conventional for a test to make sure it wasn't all in my head, and the temps went back up. Needless to say I only ran synthetic after that.
After only driving 5,000 kms in my Vette last summer, I made the yearly oil change but recycled the slightly used synthetic into my daily driver on its next oil change.
Then I drove it for the remaining 10,000 kms of life in the oil.
Yes definitely a loaded question on here. But I would not have any anxiety about doing exactly the same as you. Many will discuss acids in the oil etc left in over winter but at 2000 touring km a year, I don't think its a big deal. Switching to synthetic is never a bad thing but likely a waste of money for you as well. The yearly conventional oil change has been working good for you so far so why change your routine now.
