Considering chevy says 21/29 mpg you're already doing pretty well. I avg 27 usually with a mix of around town and highway at 75 ish mph. I don't stomp the pedal often. Besides it's an SS, not a maximum mpg barely get out of it's own way mobile. (not saying other HHR's are-just a general statement I've close to doubled the gas mileage of the truck it replaced with 4x the performance-I'm the guy from the land of happy now.

 

That's pretty much my experience, too. These things aren't very aerodynamic.

 

We may not be talking about the same thing depending if he is referring to Imperial (Canadian) Gallons or US Gallons? Since he is probably converting from Litres to Gallons I'd assume it is US Gallons but that should be confirmed.

My best tank full (US Gallons) has been 31.6 (hwy, cruise control/downhill) and my worst (city, lead foot/uphill) was 22.8. If you haven't had an oil change yet (i.e. low mileage) you could expect some improvement. I experienced a noticeable improvement after a break-in period at about 10,000 km (6,000 miles)

Measurements were computed from the odomenter reading and actual gasoline used. I found the DIC (on my vehicle) slightly inflated my numbers.

 

Let's hope it doesn't loosen up too much.

 

I figure when my engine lossens up I will have to remove gas out of the tank since I will not be able to use all the gas I am saving! LOL!!!!