Synthetic Oil Questions

[poikle27]

Hi Friends,

Might be a dumb question here, but would appreciate your insight!

As you guys know, recently picked up my Z. Is it safe to start running synthetic oil on my next oil change? Heard that it's not good in older engines? The engine was recently resealed so the seals are all new.

What are you guys running in your Z's, and what would you suggest for a Z in Southern California?

Thanks.

[ThisIsSparTTa]

What do you mean recently re-sealed? If the engine was rebuilt, its not recommended to go back to synthetic for 3000 miles, but that's for the piston rings, not other gaskets and seals. Otherwise synthetic is fine. Minimum of 10W-30 unless you're in a super cold environment (not SoCal), then you can go 5W-30. I was running Royal Purple before my rebuild.

[poikle27]

What do you mean recently re-sealed? If the engine was rebuilt, its not recommended to go back to synthetic for 3000 miles, but that's for the piston rings, not other gaskets and seals. Otherwise synthetic is fine. Minimum of 10W-30 unless you're in a super cold environment (not SoCal), then you can go 5W-30. I was running Royal Purple before my rebuild.

Sorry should have clarified, my Z has a new valve cover gasket, new oil pan gasket, rear main seal, cam seals, crank seal.

[NolimitZ32]

Beware of synthetic in old engines (well sort of): Rubber and to a lesser degree viton gaskets and seals start to loose their elasticity with age and heat cycling, this cause the seals and gaskets to not expand fully during hot operation, this lack of expansion causes microscopic clearances between the gasket mating surface. Synthetic oil molecules are smaller and therefore have a higher chance of squeezing through the space formed. In your situation, since all the gaskets and seals are new there should be no problem.

[Metacom]

There are also "high mileage" synthetic oils that claim to help older seals expand to prevent leaks. At least it'll let yah know whatever seals/gaskets to replace :P