[gone-ot]

Smurf gives a good example to consider:

A) You can use taller tires/rims to reduce engine speed in highest gear, but that entails bigger/heavier tires (more rotational mass) which may/maynot hurt final mpg results depending upon how many start/stop cycles you have to endure because additional 'rotational' weight (heavier tires) *hurts* acceleration but isn't a problem once you're at speed.

B) You can change the axle (RWD) or final-drive (FWD) gearing ratio, which does NOT increase rotational mass (good thing), but entails mechanical change out of parts, which isn't trival to those who are non-mechanically inclined...and, it's a more permanent type task.

C) ALTERNATIVE "trick" -- temporarily swap TWO tires/rims(*) only on the speed-measuring axle to test/measure the actual engine reduction & increased MPG that you get. Then, if you get results you like, actually do the axle/drive-ratio swap. DIY using decent junkyard parts and the total axle cost & installation is often LESS than four new tires & rims.

(*) NOTE - select "new" size tire/rims that most closely match the "new" axle/drive-ratio 'revolutions-per-mile' (like Smurf mentions) that you plan to install.

• New tires/rims is quickest and easiest route, and easiest to UN-do if you don't like the results; but, might not be the cheapest.

• New axle/drive-ratio is more difficult to both do & UN-do, but allows you to keep & use the tires/rims you already have (if you wish).

• Alternative "test" provides a quick-n-dirty "middle-ground" way to firsst test the results BEFORE doing the more permanent mechanical change-out.


Just a few things to mull over before actually spending your money.