For the past couple of days, I have been "playing" in the engine shed at the Tuckahoe Gas and Steam show. I am the "oiler" on the BIG (160 hp at 225 rpm's) hit or miss stationary gas and diesel engines. These engines use a total loss oiling saystem thru drip oilers. The only oil they use is Rotella 15w-40 as they have found it is the best oil to use in keeping carbon build up down, apparently it is the additive package of the oil. These engines are used occasionally. The oil has a CF/SJ rating.
I have been using Rotella 30w in my truck.
Just my 2 cents
