What motor oil weight for 1970 Buick 455 big block motor

[John Cregan]

I recently bought a restored 1970 Buick Skylark GS 455 and am wondering what weight motor and type of oil to use? When I say restored I mean that the engine and transmission have been fully restored. The previous owner said that he used synthetic oil but a local mechanic said to never use synthetic oil in an engine that old?

[misterc9]

They used 10W30 and 10W40 when those cars were new. The engine was rebuilt? Then it should be clean inside. The previous owner used synthetic oil so it should be fine to continue with it. I have used Mobil 1 synthetic for 25 years in my original 65 Mercury and 56 Chevy with good results.

[Frank DuVal]

Yep, 10W-30 synthetic will be great.👍

 

If perchance it leaks all over the ground, and why would it if it currently is running synthetic(?), then no.

[joe_padavano]

Rather than guess, the owner's manual will tell you exactly what weight oil to use for the intended temperature conditions. This is from a 1970 Olds. I suspect Buick will be similar if not exactly the same.

 

[rocketraider]

If the engine has never been torn down, cleaned and rebuilt I understand the concern about use of synthetic.

 

OP says engine and transmission are "fully restored", so if that's the case and the engine has used synthetic since then, no reason not to continue using synthetic in an appropriate weight by Joe's chart above.

[joe_padavano]

1 hour ago, rocketraider said:

OP says engine and transmission are "fully restored",

 

Unfortunately, I've seen too many engines that were "restored" with a rattle can...

[Bloo]

10 hours ago, John Cregan said:

The previous owner said that he used synthetic oil but a local mechanic said to never use synthetic oil in an engine that old?

 

Synthetic oil is fine. Any high quality oil is fine. 

[Frank DuVal]

And Joe's chart clearly shows 10W-30 as being OK for anything above 0°F.

 

If you are going to operate a vehicle in -20°F weather, that needs to be part of the question!

[JACK M]

Synthetic has very good lubricity.

You may see leaks that it never had before as synthetic will creep into places that the old oil couldn't get to.

[Marion McAlpine]

Joe Padavano is correct (as he usually is)--follow your owner's manual to choose the correct viscosity oil.  We use 10W-30 Valvoline VR-1 Synthetic racing oil in our 1970 Chevrolet Chevelle SS.  (We use the VR-1 synthetic because it was recommended by our engine builder.)

[John Cregan]

On 1/12/2022 at 4:44 PM, joe_padavano said:

Rather than guess, the owner's manual will tell you exactly what weight oil to use for the intended temperature conditions. This is from a 1970 Olds. I suspect Buick will be similar if not exactly the same.

 

Thanks for the information Joe. I appreciate it.