The power torque and horse power is very noticeable. The stock setting seems to add about an average of 6 mpg if drove at 60 mph, also with slow take off from a dead stop. Those averages go down slightly as I go through the spot and spot plus. Now as for the race setting, very powerful and noticeable from stock setting. Fuel mileage goes down to about 19 mpg. However, speed gain is very quick.
Read the reviews prior to purchasing and some mentioned battery run-down if not driven daily. It's true, pulled my truck in the garage at 4:00 p.m. Friday afternoon. went out to start it to run uptown at 4:30 Sunday afternoon and battery was dead. Remove RANGE if vehicle sits for a couple days. Would have given higher rating had it been worthy of it. Battery drain is unacceptable.