To answer your question, yes. I LOST about 2 mpg when I switched back to Delo 400. Good oil and I have no fear of hurting my engine, I just couldn't afford the Amsoil for a while. I have the oil now to switch back to Amsoil and I'm changing the entire vehicle out. Front and rear diffs, transfer case, trans, engine. The only thing I'm not changing is the power steering fluid. I'm going to have someone else do that.
I also noticed that it ran smoother and quieter right away. It also takes a whole lot longer to warm up in the winter to get heat into the cab. Thank goodness for the bun warmers.
I also noticed that it ran smoother and quieter right away. It also takes a whole lot longer to warm up in the winter to get heat into the cab. Thank goodness for the bun warmers.