I don't think I would change any gears (ring & pinnion), but you might consider a overdrive unit like gear venders? I don't know how much a few extra miles to the gallon are worth to you???? you state you drive about 30K miles a year, If you got 18 mpg now and went with the gear vender unit and it got you up to 21 mpg, you would save 238. 1 gals a year or about $ 333. 34 a years. At that rate it would take you about 7 1/2 years to recop your investment. Now, alot of people don't do improvements based on logic( just ask my wife), but some might? If saving about 333 dollars ayear, plus getting to play with a new toy does it for you, when hey why not? Most people on here spend way more then that and don't get any mpg improvements at all, some loss mpg's. You decide what you what, can afford, and can live with. Good luck.