Twenty inch rim/tire combos won't inherently kill mileage.If the overall diameter of the combo is taller than what your HHR came with,THAT is what will make the mileage seem lower(because a taller diameter rolls fewer times per mile,it gives a lower reading on the odometer).It's illusory-you're still travelling the same distance but the odo reads short.

 

On my last tank...26.8 MPG average by computer. Pretty good overall average for a car that is supposed to get 29 on the highway. 27.25 and that's all around driving with the highway miles doing 80 MPH.

 

Im at 1600 miles and my DIC says that im averaging 27.8mpg. I am very impressed with this thing.

 

Just took the first leg of a 900 mile road trip, and I'm reading exactly 28.0 mpg right now. It probably would have been better, but I had two long periods of idling, two of stop and go traffic on the highway for about 20 mins each, lots of feathering during thunderstorms, and about 3 hours of cruising at 90mph+ to make up for all that. Definitely impressed.

 

My GP is 3.8L, 200 HP and gets anywhere from 24-28 MPG depending on temperature, conditions and % highway driving.

The 2.0 turbo in the SS can get me equal or better MPG, with significantly higher HP. I'm on board with that. :)

 

Quick update, I ended up just short of 29 MPG after resetting all calculations for the return trip. Not bad at all.

 

I drove from San Diego up to Northern Utah and got 27.5 on the way up and 28.5 on the way back with my 5spd. I'm pretty sure the difference is that I was climbing all the way up and dropping altitude on the way back. I'd say I averaged about 80mph both ways. Nothing to complain about, for such a long trip this thing sure is comfy!

 

100 mile round trip. I clocked the HWY only since I knew I was going to show off the TURBO to my brother.
Going from Buffalo to Ellicottville (ski-country) is slightly uphill. 28.7 mpg. averaging 60-65

Coming home, slightly downhill and I was using the cruise mostly, 60-65...

35.5 m.p.g.

Awesome!!!

JIm

Overall, after showing off the Turbo, and tooling around, my tank thus far has yielded 28 mpg mixed. Since the dealer is the one that filled it (my car has only 300 miles) I've no idea how accurate the electronic guage is. I'll do the calculator when I fill it tomorrow.

 

filled up, 493 mileage range
did 29.4 mpg on this tank
have to see what the tune brings when it get installed....

 

Took the SS from Buffalo to lancaster, PA. Dropped the speed down to 71 and averaged 31mpg. 80=26 mpg, so did 60 so I guess that @ 70 is ideal. Ran a tank of Hi-test at 3.81 a gallon. Wow what fun but I wouldn't try to figure gas milage, I was having too much fun finding the firewall.
Jim