I have no love for Lucas oil stabilizer, but to say it is just grade 40 motor oil is not even close. It is MUCH thicker than any regular oil I have ever seen. seems to me it is about like 50% 50 wt. oil, and 50% STP, without the good zinc in the stp. Like STP, only good for the old beater with BAD rod or main bearings, to hold it together for a few more miles till it can be junked, repaired, or sold to some unsuspecting poor soul.