I've run the high end stuff here around Dallas and the low end stuff and to be honest seat of the pants I can not really tell a difference and I am no stranger to power with 2 muscle cars in the garage.. as far as MPG difference not a real difference either. I drive my car to work everyday and half the driveto work and home is always stop and go and I average 20mpg +/- .5 and I touch a 100mph every couple of days once past the traffic on the way to work. I have not seen enough difference according to the facts to get me pay the price of the high end stuff regularly.