Mechanic Q: Better MPG on 2010 Rav4?

2010 Rav4 3.5 V-6 4WD Ltd = owned since new. All reg. maint. has been done including running tire air pressure about 1 lb over recommendation. I have averaged 22.2 MPG since new. Would it help if I did 1 or both of the following 2 things? #1. Changed to Synthetic Oil? #2. Changed to more fuel efficient tires like Michelin "Latitude Tour"?

Mechanic Q: Better MPG?

Owned since new. All reg. maint. has been done including running tire air pressure about 1 lb over recommendation. I have averaged 22.2 MPG since new. Would it help if I did 1 or both of the following 2 things? #1. Changed to Synthetic Oil? #2. Changed to more fuel efficient tires like Michelin "Latitude Tour"?

Mechanic Q: Right Wheel Cylinder??

I've had my right rear wheel "lock-up" (won't move) twice (usually after I wash it), 1st time = backed up & it broke loose, 2 months later it locked-up again (after I washed it) = removed wheel & could move hup only about 1/4" each way (rt. / left) = disk pads not hung-up = tried pulling emergeny brake on/off = didn't help = pumped brake pedal several times = broke loose! (7/4/11) = checked brake fluid level = half way between high/low = has been OK since (but I haven't washed it) = do I have a wheel cylinder problem = should I have it replaced? PLEASE ADVISE.

Mechanic Q: At what mileage interval do I need to replace TIMING BELT??

1.8 L Auto Trans.