[GMMillwright]

I'm somewhat disappointed with my economy as well. Average speed is 41-42 and mileage is 38+. City driving really drags that economy down. I got better mileage in my ECO due to the manual trans. I know the delete and downpipe tune Fleece is expensive and will never pay for itself, but I'm strongly considering it now.

 

[GMMillwright]

Never weighed the wheels/tires from factory or the TSWs. The 19s are rotary forged, so I'd guess they are relatively light. The tires aren't LRR and the added 1" in width does have an effect on the mileage. Taking all that into account, still not 100% satisfied. I drive the speed limit on the highway and baby it all the other times. Always looking for the next upshift and routinely see huge instantaneous mpgs. Just doesn't seem to materialize into 40+ averages per tank. Just frustrating.

 

[GMMillwright]

stock: 215/55/17
new: 235/40/19

Only 3 revolutions per mile difference. Less than 0.5%.

 

[GMMillwright]

Have only taken one long highway trip with the car so far. Didn't even have 1000 miles on the clock, so still not broken in at the time. Averaged mid 40s as expected. City and stop and go driving really drag down the average. Much more than when I drive my ECO (manual).