I have the 4.7 engine with 155000 miles on it and recently switched to Amsoil 5w-20. In 2 month’s 2000 miles I lost 3 1/2 quarts of oil. It’s not leaking. I was told by another mechanic to switch to 15w-40. Is this a wise decision or will this be detrimental to my truck?
Did it use oil before you switched ? If not go back to what you used before and see what happens . Of course it should be what is listed in your manual .
It was using about less than a quart every 3000 miles
The oil usage MAY drop back to previous levels if you keep using Amsoil. The synthetic can flush a ton of junk out of the engine so do the next change now if you want to keep using synthetic. This exact thing happened on my '89 Suburban 350 with 96K miles. Oil consumption went back to a quart every 3000 or so after the next change.
Or go back to conventional. Don’t use 15w40, it is way too thick for most modern engines.
What is the thinking by doing an oil change now? I definitely would like to continue with Amsoil.
Why would you do that ? You used it started getting more oil usage . Is that not a clue that maybe that was not the best move .
If Amsoil has cleaned a bunch of crud out of the engine, you don’t want to leave that in the engine for 5000 miles, do you? Pull the dipstick and look at the oil. If it is really black, change it.
All the 15/40 oils I know are formulated for Diesels. They have different additive packages. May not be harmful, but why take a chance?