My Pontiac Firefly / Chevrolet Metro / Geo Metro / Suzuki Swift welcomes fuel efficiency nerds everywhere

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Latest fuel economy stats
for my '98 Firefly 1.0L 5-speed
  best: 2.3 125.1 104.2
 worst: 6.4  44.1  36.8
prev.3: 3.3  82.3  68.6
   all: 3.8  73.4  61.1
L/100km | mpg IMP | mpg US
Jul 28/07: more, graph, calc.
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Best non-hybrid MPG: Mitsubishi Mirage
Highest MPG for a new car: Mitsubishi Mirage?
Mitsubishi's 1.2L, 3-cylinder Mirage is the first new non-hybrid car that can match an old Metro's mileage. The company says 44 mpg (US) highway, 37 city. (Some drivers are already beating that in various economy driving contests.) How? An efficient engine, very light weight and aerodynamic design.

Cheapest to own? 2015 Nissan Micra Forum
2015 Nissan Micra Forum
The Micra's fuel economy isn't its most notable feature -- the $10,000 price is. That makes it one of the cheapest cars to own. And its 109hp, 1.6L engine and good power-to-weight ratio means it's fun to drive too.

Latest 10 posts:
1. Recipe for getting 99.7 mpg from a Geo Metro
2. - famous aerodynamic Honda Civic gets a web site
3. Snapshot: effect of tire pressure on rolling resistance
4. 65+ vehicle modifications for better MPG
5. Metro mania: forget stocks, put your money in old Geos!
6. 100+ Hypermiling / ecodriving tips for better gas mileage
7. Experiment: how long should a block heater be plugged in?
8. Everything old is new again: Car and Driver magazine modifies an econobox to improve MPG
9. Project Convertible XFi: alfresco efficiency
10. The floor is yours: MetroMPG opens a fuel efficiency forum
11 ... 64. Show all posts

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Good MPG forums: I spend a lot of time at and have also been known to lurk around

Chevrolet Aveo forum - discussion of the Chevrolet Aveo and its siblings (Pontiac Wave, Pontiac G3, Suzuki Swift+, Daewoo Kalos).

> Lots more Metro links...
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Send me a note:
darin AT metrompg D-O-T com,
or here

MetroMPG has opened a fuel economy forum
Read about the project here, or go straight to
ScanGauge fuel economy computer Save fuel with a ScanGauge II fuel economy computer.
I personally recommend this tool. I've owned both versions (I and II) and can't say enough good things about it. If you're serious about saving fuel, get one.

For more information and to order, visit EcoModder.

9 reasons why your winter fuel economy bites!

Posted Saturday, November 12/05 in General

Icy road sign

As if we really needed another reason to hate winter.

Those of us living in northern climes have already started to notice the seasonal decline in fuel economy, even with careful attention to sagging tire pressure (probably the best known effect of the mercury's slide).

Yet, despite diligent all-around maintenance and continued careful driving, cold weather fuel consumption can be dramatically worse than in warm temperatures.

How much worse?

Have a gander at these calculations for a Honda Civic hybrid at 60 MPH in varying ambient temperatures:



Look at the extremes: the coldest MPG is 28% lower than the warmest. (Source.)

My own experience supports this: 12.5% worse mileage during the colder half of the year (Oct 15 to Apr 15) than for the warmest half (Apr 15 - Oct 15), on average 2002-2004 in my 1989 Accord. Comparing just the warmest months (Jun-Aug) to the coldest (Dec-Feb), the difference is even more apparent - 21.2% worse (2002).

Why so bad? Off the top of my head, I could think of a couple of reasons to explain it, but together they didn't seem significant enough to account for the magnitude of the change. With this mystery to solve, I hit Google. And here's what I learned...

9 reasons your winter fuel economy bites

1. More idling

This should be a no-brainer, yet parked idling cars are a common sight in cold weather. Resist the temptation to idle your car to warm it up. An idling engine gets 0 mpg. Consider also that idling the engine does nothing to warm up the tires and drivetrain.

Even in the coldest weather, you can begin driving after 30 seconds from a cold start - keep speeds low/moderate and use gentle acceleration until the temperature gauge starts to climb (source).

2. Low tire pressure

Of course you're smart enough to keep up your tire pressure as the temperature drops, right? A 10-degree (F) change in ambient temperature equates to a 1 psi change in tire pressure (source). Fuel economy declines 0.4 percent for every 1 psi drop (source).

3. Increased rolling resistance

Even if you're completely attentive to proper tire pressure, cold ambient temperatures will still cause your tires to return worse mileage. That's because a tire's shape isn't completely round - the sidewall bulges out at the bottom, and where the tread meets the road the small contact patch is actually flat. As the tire rotates, it constantly deforms to this shape, and this deformation requires more energy when the rubber is cold and hard. Rolling resistance at 0 degrees F is 20% greater than at 80 degrees (source 1, source 2).

4. Crappy road conditions

It's increased rolling resistance of another kind: driving through slush and snow. And then there's its wasteful polar (no pun intended) opposite: no friction at all! (A.K.A. wheelspin on ice.)

5. Lower average engine temperature

In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.

A block heater can offset this problem (improving fuel economy by 10% in sub-zero conditions - source), as can garage parking, and combining trips (to minimize the number of cold/hot cycles).

Also related...

6. Higher average lubricant viscosity

Engine oil thickens as it cools. So does transmission and differential fluids and even bearing grease. Significantly more energy is needed to overcome the added drag these cold lubricants cause.

Using synthetic fluids can address this problem, since their viscosity changes less at extreme temperatures than traditional mineral fluids.

7. Weaker gasoline

Gasoline doesn't vaporize readily at very cold temperatures. So oil companies formulate fuel differently for cold-weather markets in the winter. Unfortunately, the changes that provide better cold vaporization characteristics also result in less available energy for combustion. You won't get as far on a liter of winter gas as you will on a liter of summer gas. (Source.)

8. Higher electrical loads

In colder temps, you use electrical accessories more often:

- lights (in higher lattitudes it's darker in the winter)
- rear window defroster (because it's easier than using the ice scraper, right?)
- heater blower motor (I don't have a/c, so this isn't balanced out during warm conditions); heated seats/mirrors
- windshield washer pump (because it's easier than using the ice scraper, right? And for frequently cleaning off dirty road spray.)

9. More aerodynamic drag

No, I'm not referring to the layer of snow you're too lazy to brush off the top of the car (though that would hurt mpg too).

A vehicle’s aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2% (source). logo - fuel economy forum
Read what visitors have said about winter fuel consumption at - join the conversation!


Links & Resources:

Anything I missed? Let me know.

EcoModder fuel economy forum Note: MetroMPG has opened a fuel economy forum
Read about the project here, or go straight to

darin AT metrompg D-O-T com, or here