25W70 in the USA?

[rslifkin]

I think it's a Castrol oil, so it may be available elsewhere. I'm sure it's not easy to find though.

 

[vintageant]

CATERHAM's advice on finding the cheapest conventional 20w50 and adding STP or similar makes sense.

STP have 3 choices: Oil Treatment, Engine Stop Leak, and Smoke Treatment. Bar's, Bardahl and Casite all make similar Smoke Treatment products.

Which one to choose?

 

[addyguy]

Amsoil has 2 straight-60 weight oils to choose from.

Amref's 'Penngrade-1' high-performance oil comes in grades up to straight 70....that's probably pretty close to what you are looking for, and is decently priced.

I know it is frowned upon here, but Lucas oil treatment is probably a good idea here - it's an extremely thick brightstock. Adding a quart of that to a 20W-50 would get you in the range of a 25W-70, and be a LIOT cheaper than STP...

 

[vintageant]

Thanks addyguy,

Amsoil are all synthetics. I'm staying with dino. At my local store STP is $2.99 for 15 oz or 20 c per oz. Lucas is $11.99 for 64 oz or 19 c per oz, so trying to understand why you say Lucas is a LOT cheaper.

Read many of the posts on Lucas (& STP), but they all seem to be opinions, and most not related to a 74 year old engine.