SAE30 Oil 10W30

The manual for my inline 6 ask

The manual for my inline 6 askes for SAE30 oil. The only one they sell at the local NAPA store is apparently for diesel engines and according to the sales guy it has additives meant to clean the diesel engine and he sais that they would remove carbon build up in older gas engine and hence cause them to not be tight anymore and leak oil past the rings.
Is it save to just use 10W30 weight oil?
Inline 6 GM 250CID early 70's

I'd have to disagee with t

I'd have to disagee with the salesman. He probably meant well. Crankcase oil for diesel engines is rated differently from oil rated only for gasoline engines . People who have diesel engines should be aware of that. You can use diesel rated oil in either diesel or gasoline engines satifactorally.
The expert advise about viscosity is that you should NOT go to a multi-viscosity after having usied straight weight oil. That sometimes will cause oil leaks. You can go the other way and change from a multi-viscosity to a straight weight although you should not need to except when the engine is old and extremely worn.
There are a lot of myths about motor oil so consider the source. Generally a skilled mechanic is a better bet.

i've used delo in about ev

i've used delo in about everything for years without problems. how's your oil pressure? if good 10/30 should not be problem. most manufacturers call for 15/40 now. used to demand straight 30 on same product.

"dont know the oil pressure ye

"dont know the oil pressure yet, since I didnt get this engine started yet. One step at the time, waiting for a new carb and some other bits and pieces."

"It's hard to go wrong wit

"It's hard to go wrong with a 15w40 for diesels/gas, like the delo, Rotella, etc. Have run 15w40 for 15 years in my Mercruisers, although Ive used a Schaeffer brand thats a 150 year old company but nobody's ever heard of them except in mining and industrial applications(just a comment-you don't need to use this brand). 15w40's are built for heavy use like a boat engine which is comparable to some heavy duty diesel engine applications."