Originally Posted by Gokhan
Originally Posted by jongies3
Recently bought a 1989 Econoline RV with a 460 in it. Only 72k miles on it, should I use 15w40 in it for higher zinc as this is a flat tappet engine I assume? Figure it would appreciate the thicker oil due to the heavy weight of the vehicle and possible towing a car/or ATV trailer behind it occasionally on trips, heat of summer and what not or would 10w30 be fine?
I have a lot of Rotella leftover from my 7.3 diesle that I sold that needs used up anyway! Just wanna make sure this is okay for the engine as I don't know much about them.
Yes, if it has flat tappets, 15w40 is the way to go -- not because of the ZDDP but because you need a thick base oil. A typical 15w40 has almost twice the base-oil viscosity of a 5w30, which is what you need to protect the flat tappets.
You don't need high ZDDP. Besides, most of the latest 15w40 oils don't have high ZDDP.
The only concern is if you can start with 15w40 in the winter in Montana.
See my base-oil viscosity (HTFSV) tables posted in the white-papers section for more details.
I've read your posts but still i find it hard to believe that really flat tappets don't require high ZDDP with modern oils, i've seen how for example modern Castrol GTX wiped out the cam in a friend's Triumph TR6, and it seems like Castrol GTX doesn't have more than 600-800ppm of Z&P these days.
He now uses Valvoline VR1 20W-50 in it , which i recommended to him and the engine is running perfectly with a new cam and tappets.