"Give it a try. Generally speaking cold air is supposed to be better."


That's what I thought, too - that cold air is better. I'm gonna start with MAF cleaning. If I don't hit my target (28 - 29 average) after that, I'll go for it. A short section of flexible pipe from the back of the air-box straight down between the engine and manifold cover will do it. Piece of cake. If it doesn't do anything (or worse) just cover the hole in the box. We'll see...

Cold air is supposed to be better, however when it's 'very' cold, and the engine has a hard time warming up, it stays in its 'warm up' mode longer, which runs richer and isn't as fuel efficient. Its really hard for me to stay above about 22-23mpg here in Fargo when the temp is consistently below 0F

I really noticed that tonight. When leaving work I started the carwagon to warm it up. Turned on the defrost both front and back. Cleared the snow and ice. Took, at most, 10 minutes. When I got back in the carwagon my fuel average dropped like a stone - from @ 25.5 mpg (when I arrived at work) to @ 20.5 mpg upon driving away. And it never recovered all the way home. Now I know the ac compressor will run on defrost mode and the rear defrost is also a drain but the sudden, significant drop doesn't make any sense to me. It's a very gently driven 2.2. It shouldn't be THAT bad. My old Ranger with a 2.3 gets better mileage than that. It's starting to bug me. Here's a thought: a hotter thermostat maybe?

Remember that an idling engine gets 0mpg, hence the proliferation of Start/Stop systems on newer cars and trucks, plus an upcoming Federal mandate to make them standard on every U.S.market vehicle by 2016.

Letting an engine idle to warm it up will kill your average mpg, although in some circumstances, it's unavoidable.

So even if your not moving the clock is still ticking, so to speak. And the newest systems try to avoid that? I'm not sure I understand.

Basically the system that computes the instant mileage readout for the DIC looks at fuel flow, throttle opening, engine run time, and average road speed to come up with the figure displayed.

When it's just sitting there idling you're still using gas(fuel flow), and the engine is still racking up hours(run time), but you're not doing anything more than that.

Idling uses up roughly .4 to .7 gallons per hour according to GM's figures for their industrial engine equivalent to the Ecotec four.

As an experiment, the next time you're out driving, keep the instant mpg display up on the DIC, you'll see your average mpg drop slightly at a long traffic light. Because you've gone from say 26mpg down to 0mpg, and that will lower your average.

Start/Stop systems improve overall mpg in vehicles so equipped by roughly 10-15%, but the tradeoff is a lag in restarting after brief stops, and customer resistance due to the odd feeling of having the engine "stall" all the time. I've driven a BMW equipped with Start/Stop and it's a bit jarring at first when the engine dies at every stop, only to snort back to life when you lift off the brake pedal.

I see. But other than brief warming-up periods (when gas is used without moving) can that fully explain the pattern of poor gas mileage in cold weather? I'm tending towards thinking something else is also at play. Quite honestly, I've never heard of such consistently low mpg in an almost new, 2 wd, 4 cylinder vehicle in cold weather. Have you?

I don't doubt most of the numbers reported. But it runs the gamut. No consistency whatsoever. And it's disappointing to think I might have to move to Texas to get better gas mileage. No offense to Texans.

With all the low temps here lately my fuel mileage has dropped also. I remember years ago the fuel company's would change there fuel formula for winter time weather. It was know to decrease fuel mileage.
Wonder if they still do that?

I'm thinking the "terminal warm-up mode" is to blame, now that I think of it.

A hotter thermostat will just make your engine run hotter,not warm up faster. I was wondering this for a while. I'm able to get heat from the heater after driving less than a mile. I have never had a car warm up so fast,let alone a 4 banger. My mileage has dropped a couple of MPG s(coldest winter I can recall) but nothing like some of yours. Since mine warms up so fast, could this be why my mileage hasn't tanked? How fast does other warm up?