Hey, I am a mobil1 junkie but not in Rotories, bad ideas, even with oil metering removed. David88vert hit the nail on the head with the link he posted. I use Valvoline VR1 and change every 1500 miles, not a daily driver though so if you DD then a little longer is ok too. I have not bought into the whole idea of premix yet, it tends to wear out plugs too quick for me, and at $15-$20 a plug, thats too much maint. for me and I cant seem to see the effects. And BTW never run premix with emissions car, the cats will hate you for it and raise your EGT's to a very high number and melt the cats down.....Seen it happen. Thanks and God bless