I scored some free oil today from my boss, shell Rotella 15 W 40 heavy duty diesel engine oil. Is this oil good for olds big blocks?

 

Yes, how old is it?

 

Does oil go bad?

 

I hope not, I bought a BUNCH of Shell Rotella 15w40 about 10 years ago cuz I heard they were lowering the Zinc. I use that oil in my Olds and old truck.

 

I use Shell Rotella T4 all the time in my 71 and 96 Oldsmobiles; as well as, my 86 Ford F250 with a diesel engine.

 

I heard the zinc content of the Rotella oil was reduced from its previous recipe, but even now it has more zinc than regular oil.

If your using a flat tappet cam with pretty heavy valve springs, I’d suggest using a racing oil like Valvoline VR1. If it’s a well worn engine with a mild camshaft/springs, the Rotella will probably be fine.

 

Some manufacturers state 5 years as a shelf life. Is it to get us to buy more oil? I don't know. Is the additive package breaking down? Same, I don't know.

It could be to keep users reasonably close to proper modern oil specs for the majority of cars on the road to reduce liability.

Saw a minute amount of "silt" on the bottom of a sealed oil can that had been setting for a very very long time in a shed. Have also noticed the color of oils getting darker that have sat for many years. Maybe that oil was dark in color when they were made.