With financial markets in a historic tailspin, it's a good time for belt-tightening. One of the best ways is to tame that cash-eating monster: your car.

I was perusing the OneThingCT Web site, which offers a collection of one-off things anyone can do to reduce personal energy consumption. One suggestion is to put your car on a diet, and the idea appealed to me.

It's a strategy with numerous benefits: It can save money, help the environment and make you healthier too.

Estimate how many miles you drive every week or month. Then give yourself a budget -- the total number of miles you allow yourself to drive over a period of time.

The point, of course, is to be stingy. At the very least, you want to allow yourself only enough miles for commutes and errands that are absolutely necessary. But if you want to cut costs and perhaps spur a change in your lifestyle, allow yourself a mileage ration that's between 10 percent and 25 percent less than what you drive now.

Seeing how much you're saving can provide good inspiration. So here are calculators and other resources to help you.

RideShareOnline shows you how much you spend on gas while commuting, alongside how much you could save by splitting the cost with carpool buddies. DriveLessSaveMore goes one step further by showing you how much you would save per month, week or year by cutting down on driving by 40 percent.

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These calculators require mileage estimates, as well as your car's fuel consumption and the price of gas. If you don't know these things offhand, you can use Google (GOOG) - Get Alphabet Inc. Class C Reportmaps to find distances. The Department of Energy lists weekly gas prices nationwide, regionally and in select states and cities. The DOE also provides fuel consumption stats for most cars.

To support you, DriveLessSaveMore offers tools to organize errands so you can combine trips and go about your rounds efficiently. It also has a pledge card you can mail in, promising to take mass transit, bike, walk and carpool.

If you might be willing to hoof it, car pool or put foot to pedal, my August column on walkable cities has resources you'll find helpful.

To put your own auto diet in perspective, check out the blog for NoImpactMan, a New Yorker who swore off cars and most other environmentally bad stuff for a year

For some final inspiration for mileage trimming, consider this: If your car gets 21 miles per gallon, for every mile you walk or bike instead of driving, you save more than a pound of carbon dioxide emissions. For other CO2 comparisons, check out a handy chart from the Sightline Institute.

To find out your car's carbon footprint, use Terrapass's calculator. If I reduced my annual mileage by 2,000 miles to 10,000 miles in my Toyota Matrix, I would cut my carbon emissions to 6,987 pounds from 8,385 pounds. I'd also trim more than 15 percent off of my gasoline spending.

All around, this is some slimming down that I could live with.