Dear Dr. Don,
I'm 19 years old and have a big problem on my hands. I work as a civilian for the government and need a way to save money on gas.

My current ride is a 2004 Chevy Silverado LS extended cab. I'm paying $400 a month on a loan that is in my uncle's name, with a loan balance of $12,500.

The truck gets about 15 miles per gallon in the city and 25 mpg on the highway. I live about 30 miles from work and there aren't any mass transit or carpool options available to me.

I drive an hour to work and another hour back home. My vehicle has a V-8 engine with a huge appetite for gas. It costs me about $120 to fill up the tank every week and I think that my money can be put to better use -- like on a new car.

Getting that new car is the problem. My mom can't help, because she has bad credit after trying to help out my sister. My father doesn't want to help me by co-signing a loan.

What do you recommend I do? I'm tired of spending my money on something that is just digging me a hole that I soon won't be able to jump out of. Also, how can I establish credit on my own without a co-signer?
-- Jay Guzzler

Dear Jay,
I'm not sure a new car is the answer. The trade-off between car payments and fuel costs is hard to make work. Building a credit history is a separate issue that I'll address a little bit later in the column.

You really want to consider all the costs associated with each alternative. Edmunds.com has a feature on its Web site that lets you evaluate the "True Cost to Own" a vehicle. It considers depreciation, financing, insurance, taxes, fees, fuel, maintenance and repairs when owning a new (or used) car for five years.

It then combines these costs to arrive at an average cost per mile.

If you average 20 mpg with the truck, and can improve that to 30 mpg with your new ride, you've cut your gas bill by one-third, as shown in the table below:

Fuel-cost savings

That's great, but the fuel savings of $1,333 a year in this example shouldn't be enough to get you into the dealership. You can create your own table and adjust the variables to reflect your driving habits, but the bottom line is that it's hard to use fuel costs as the justification to buy a new car.

That can be especially true when you consider the financial hit you might take when selling or trading in the gas-guzzling truck.

It's all a bit problematic if you aren't able to pay cash for the car and you don't have the credit to get a car loan. Work on saving gas by driving slower, taking fewer trips that aren't related to work, keeping your tires properly inflated, etc., while you build a credit history.

The best way for you to build a credit history is to take out credit in your name and pay the bills on time, every time. Just starting out, you may need to start with a secured credit card.

If you're in school, often a credit card company will approve a student card when you otherwise wouldn't be approved for credit. Earlier columns, "Get secured card to build credit" and "Students should build credit slowly" explain the two approaches in greater detail.

To ask a question of Dr. Don, go to the "Ask the Experts" page, and select one of these topics: "financing a home," "saving & investing" or " money."