It has the API SL rating, but is not "energy conserving". This is the same as the 10W-40 Supreme that you are currently using. Unless cold starting is your main requirement, 15W-40 is superior to 10W-40 (conventional) due to the slightly heavier base oil and less VII's.
The endless debate is over the issue of additive levels. Delo has higher levels of additives to deal with turbodiesel engines. I think that is a benefit to gas engines, others think it a minus. Both my '92 BMW and '94 F-150 like the stuff.
[ October 14, 2003, 10:33 AM: Message edited by: Jimbo ]