I have looked at some other posts about motor oil, had a couple of questions maybe get some input on. I inherited from a late relative about 4 cases of Rotella 15W40 and 1 case of Shell 15W40 and was wondering would it hurt to use this in my truck during the summer months, I know its pretty good in diesels. Other posts have said that some use it , just getting some input here.

 

If you don't mind getting even less mpg, go for it...15w40 HD oil has higher levels of detergents and anti-wear additives than 5w30 or 10w30...however, due to it's thickness, there's more rotational "resistance" if you will...you should notice a drop in mpg...now if your engine is on it's last leg, 15w40 may help it go awhile longer...the thicker oil will help compression, minimize blowby, etc...using it in a newer engine with tight bearing clearances and such, you may get alot of startup noise, since it's thicker, it will take longer to get to the valvetrain.

So, pretty much equal pros and cons tho the cons outweigh it for me...I personally wouldn't use it in my truck...but when I traded in my '00 Trans Am and '91 LeSabre with 198,000 miles on it for my truck, the Buick had 15w40 Rotella in it...stopped the smoking pretty well.

 

I would just find someone who owns a diesel and sell it to him. Use $$$$ to buy synthetic oil for yours........