Engine Oil. What Grade to use?

[jonsm114]

I have a 400 Express Cruiser with twin 340 horse 7.4MPIs. It is a 1996 with 425 hours. I know Oil has changed in 20 years and I am interested in suggestions relative, using modern synthetics.

Opinions?

Thanks,

Jon

 

[paulswagelock]

Use a 15w40 dual rated oil like Delo, Delvac, Rotella or Premium Blue. $12 a gallon at Wallyworld.

 

[hottoddie]

Mid 1990's are when engines converted to roller camshafts. The MPI engines I believe had roller camshafts so any high quality 15-40 oil should be fine. If your engine has flat tappet camshafts then you need an oil with ZDDP additive. I use Valvoline VR! racing oil straight 30w. It has the zinc (ZDDP) additive already in it. Keeps the camshaft and lifters from wear too fast.