My typical speeds on the highway to/from work are 70-80 mph. I have found that as the vehicle has gotten more miles on it, there's been some improvement in the mpg. An even bigger improvement has come along since the weather finally got above 35-40 degrees Fahrenheit.
I'm hopeful that this will greatly benefit us on our vacation driving down to Florida at the end of May.
Variation in mpg affected by the Gov't mandated less polluting (read that as less mpg) Winter blends. Greater mpg increases once the car is broken in and moving parts mated/seated. Also as mileage increases past certain set points in the controlling algorithm, the software programming evolves. For example many engines have a break-in cycle that kicks up the engine rpm for a certain number of miles to offset the increased friction in the green engine - as the engine breaks in and the mileage set point is passed, the rpm will drop to compensate. The 9 spd. software contains a similar for subroutine for break-in period (mine was about 3K) with increased slippage for smoother engagement for proper surfacing/mating of its unique lower gear Sprag clutch surfaces. Combine this with other subroutines built into the software that affect the refill times for the servos as they learn the driving characteristics of the driver and hopefully you end up with something that gives you and Gov't CAFE standard the best mileage possible with the least intrusive quirks to get there.
That's likely the basis for the dealers' flush and software reprogram procedure for jerky tranny complaints. Won't have any affect if there is a true mechanical defect in engine/tranny sensors or components, but if jerkyness was the result of completion of the break-in cycle, poor driving habits affecting learning of shift points, oversensitivity to the more manual tranny feel of the new design a software reload should make it respond like out of the box (for about the same amount of time).
So given the above.....should be, the more miles you drive it the better the mileage. At 9K miles running on the original 8/18 software programming I was able to ave. 30 mpg in 2WD on a 350 mi. straight flat run to the Jersey shore (including a few 0-60 in 6+ sec. blasts exiting toll booths).
