Gas prices are on the rise once again, but some of the strategies for chipping away at the cost of a fill-up are changing.

For example, this past week I stopped using a cash-back credit card that's been reducing my fuel expenses for the past six years.

It used to be a sure thing that you could get a nice discount by signing up for a gas company's credit card. Typically, it would be a no-fee card with discounts on every gallon, which is a good deal if you always pay the bill in full, on time, without any interest or penalties.

I signed up for a BP Visa card from Chase in 2006, tempted by an offer of 10 percent back on gas for the first three months and 5 percent back after that. For years I've been getting rebate checks, small ones, but every little bit helps.

But my BP card has become part of a trend toward less-generous credit card rewards. On March 3, the issuer changed the terms, so instead of getting a 5 percent rebate on fuel purchases, a BP cardholder could get 2.25 percent back, or a complicated variable gas-price discount that varies with the size of a vehicle's gas tank.

No thanks.

It's almost as if the people at BP decided to compete with Shell to see who could have the most annoying rebate program.

With the Shell "drive for five" card from Citibank, in order to get any rebate, you have to first buy 45 gallons of Shell fuel during a monthly billing cycle, which is more gas than a typical driver with a fuel-efficient car would use.

If you use that much Shell gas, the rebate is just 5 cents per gallon on fuel purchased during that billing cycle, capped at $60 in annual rebates. You would have to buy 100 gallons monthly to hit that $60 cap.

Again, no thanks.

Of course, these and many other credit cards come with high interest rates, but I'll skip over that, because if you're carrying a credit card balance, forget about rebate deals on gas and focus on saving money by paying off those credit cards.

If you are looking for the best credit card for gas purchases, start by not focusing on gas. A dollar saved is a dollar saved, so just look for the best deal.

You could get a no-fee Exxon/Mobil Mastercard and save 15 cents per gallon, plus cash back on other purchases. Or you could get a Hess Visa card and get 10 percent back for the first 60 days and 3 percent (about 11 cents per gallon) after that.

But if you were to sign up for an American Express Blue Cash Everyday card instead, you would get a $100 cash rebate if you used the card for $1,000 in purchases during the first three months. That's on top of 2 percent back on gas, 3 percent on groceries, and 1 percent on the rest, with no annual fee.

Southwest Airlines' credit card isn't a gas card, either, but its latest offer gives you 25,000 Rapid Rewards airline points for signing up, with a $69 annual fee, and cardholders can trade in their points for gift cards. For 24,000 points you could get $200 in gas cards, worth $131 more than the card fee.

When I consider credit card deals, I weigh how much money I could save against the hassle of having another bill to manage, and I look at the rules of the program. Some cards apply cash-back payments to your statement, while others require you to call or go online and ask for a check.

Lately, my fuel savings have been coming from a grocery store promotion, rather than credit cards. I've been buying the discounted gas cards offered at Harris Teeter grocery stores. They'll sell you a $25 gas card for $20 each time you spend $40 on groceries.

That's not as good as the $10-off coupons Harris Teeter used to run every week in some areas, but it's still a nice deal.

Of course, if you don't want to bother with credit cards and grocery store programs, the most sure-fire way to save money on gasoline is to drive less, avoid aggressive driving and keep tires properly inflated.