I work for a Mitsi dealer, and Mitsi have their own oil which we use on any vehicle under warranty, and as Mitsi is only about 40% of our work we use it on all other late model vehicles. Older vehicles get a 15W-40 from our bulk tanks...pumped over from a 205 litre drum. Even though Mitsubishi make everything from aircraft to pencils, I don't think they have their own refinery....I'm pretty sure it's BP.