Dog's simple solution to solve this dilemma: Reconnoitre 350 miles approx and yer tank's on last quarter ready for fill. Umm, yer fuel guage works dont it?? Thus 10 tanks of fuel deserves oil change!! Hence throw away the hour meter as bein near useless, mark notepad and/or stack fuel receipts, thats all ye gotta do.

Basically: each fillup x 10 = oil change....... nothin simpler than that.