If I might add to this ... I've found that my gas mileage has been dropping despite the same loading and driving conditions in the last few weeks. I've gone down from 31mpg average to just over 29mpg average, and I think it might be due to the winter mix gasolines: the drop started right at the time the local gas stations switched to winter blends.

 

Thanks all for the feedback, I guess I did not want to believe the lack of fuel mileage was due to my mods, but it sounds very likely. Thanks all, Todd(Uma)

 

OK... what on earth did you do for $200 that bumped your mpg's up to 36?!?!? My wife is about sick of her ride ('07 2.4/auto), ready to trade it off 'cause the best mileage she's ever gotten was about 29 mpg (one tank) - mostly it hovers around 22-25 mpg, and that's 80-90% highway mileage.

 

What speed do you run on the freeway? The Ecotec's maximum fuel efficiency, I've found, hits right around 65mph. Any slower or faster and economy suffers. With the HHR if you have no lowering suspension, it also helps to have some weight in the back end, weighing it down enough to cut down on drag.

 

Highway speed is mostly 70 - some 65... and there is typically not much in the rear. Since KY recently up'ed their interstate speed limit to 70, you risk being run over at 65 - you get passed left and right at 70 as most on the road run 75-80.

I have only one mod to the car - and that is one of the in-the-tube vortex thingys just above the throttle body. I've half a mind to remove it as I think it's useless.

 

I'm not sure if people consider this, but in the winter your car idles more. (i.e. while you're clearing ice/snow, just letting it warm up, etc)

Your vehicle is using fuel but no miles are being added. Also, in cold conditions more fuel is required to start a car and keep it running until the engine gets up to temperature.

I believe this is what causes most cases of 'mysterious' mpg decrease.

 

So... can y'all help validate the following:

• Increase tire pressure - 50 psi or so (a no-brainer).
• Premium fuel - does this matter from an MPG perspective? We typically run regular. If you're not pinging, does the octane really matter?
• Fuel additives? I own a Duramax diesel and I know that fuel additives make a real difference in diesels; does that carry over in any way in the 2.4?
• Reflash the ECM - I've read that dealer reflashes can help if you're getting poor mileage. Myth or reality?
• Does anyone make a throttle-body spacer for the 2.4? Some of the guys on the Ford Expedition forums swear that the throttle body spacers (which supposedly create a vortex in the intake mixture).
• CAI - From what I've read out here, the stock turtle is pretty efficient. Is there any net benefit to replacing it? I've no interest in making the under-side of the hood "cool" or exciting. Just better mpg's.
• Exhaust - Not really interested in more interior noise, though I don't really care if it's louder outside. I've read that some rather radical exhaust mods require additional ECM mods to make things work right.

If anyone has specific recommendations, thoughts, etc. on the above, I'd really like to hear them. Links within this or other online resources would really be appreciated. If I can't get the mpg's up on this car, it'll get traded... and I'd just as soon not have that happen. Thanks in advance for any assistance!

 

Increasing tire pressure that much isn't a good idea. You might gain some mpg, but you will spend the money you save on new tires.

I drive pretty aggresively, but I still get around 28-29. Most of my driving is split between country roads and city.

 

I drive about the same, 75% highway and 25% city in a 2007 2LT and average about 22 mpg or less. I don't drive it hard either. I was VERY disappointed as I was counting on 25 mpg minimum. Makes a difference at $3plus per gallon of gas.

 

I am usually running around 23 - 27 depending on how I drive and how long it gets to warm up now that it is cold out. I still look at it better then my old Dodge got. 16 at best. No matter how I drive or what I do, the HHR will get better then that and probably most of the cars out there. Sure I was hoping for more mpg too, but still with the weather and all things considered, I'm not to dissapointed.