Follow Tone's suggestion- I rocked all Mobil 1 synthetics A to Z. I had to do it in 2 steps. I must say the biggest differrence was in the diiferantials(don't forget the additaive in the rear), I noticably got better rolling resistance. Tranny, transfer case,+ and I suggest Mobil 1 0w-30 syn, which is rated as an enhanced fuel formula. Amsoil makes really good engine syn as well-What is the arithmatic on it?? well, I haven't done the full data thing but I have noticed a difference, and the soft foot on an easily heavy pedal helps as well. and lastly my ex wife is here from Norway and she laughs at how all sensitive we are about paying 2 dollars per gallon. Last I was there we were dropping 4$ per liter!!! and they produce lots of the stuff up there, so talk about rubbing it in. Good luck and hang in there. Everyone is feeling it plus-I try to not be judgemantal but going from a VX to a prius is what it is-