Denise Trowbridge shares some tips to cut your bill at the pump.

I've had a splitting cheap-ache for months. It's that sharp pain I get in the thrifty part of my brain when I have to pay more than $20 to fill up the gas tank of my fuel-sipping Honda Fit. Since March, it's cost me about $35 each time, which seems like a lot even if the mileage is compromised by the sheer mass of the two giant 40-pound toddlers in my back seat.

Sure, we all know we should be driving less, combining errands for fewer trips, and lifting our lead foot off the accelerator pedal. But even if you use gas judiciously, you eventually have to pull into the station and fill up, so it pays to spend a little bit of time thinking about how to cut that gas bill.

Luckily, I have a prescription for the gasoline cheap-ache - leverage the money you're already spending to lower your real price-per-gallon.

It's getting easier. As gas prices rise, more retailers offer gas perks to lure in shoppers. For instance, CVS is running a promotion offering a $10 gas card when you buy $30 in participating products. Speedway gas stations offer 10 to 50 cents off a gallon to Speedy Rewards members who have earned enough points.

Many of us already use grocery-store loyalty cards such as those offered by Kroger and Giant Eagle. But I ask you - are you really maximizing those discounts? Let's see.

At Giant Eagle in Central Ohio, you earn 20 cents off per gallon at GetGo stations for every $50 spent on groceries, gift cards or prescriptions, said company spokesman Dan Donovan. In their weekly circular, Giant Eagle advertises other special offers good for more points. Fuel discounts can be redeemed for an amount up to or equal to free gas, on a one-time fill-up of up to 30 gallons.

Kroger offers 10 cents off a gallon at any Kroger, Turkey Hill or participating Shell station for every 100 points earned. One point equals $1 spent. Most prescriptions earn 50 points every time they are filled, and every dollar spent on gift cards earns double points. The maximum discount is $1 off per gallon, on a one-time fill-up of up to 35 gallons.

Bear in mind the points earned per dollar spent are the total after coupons, not before.

Using these programs casually will likely save you the occasional 10 or 20 cents off a gallon, but "unless you have eight kids and only shop at one store, you aren't going to earn enough points for free or substantially discounted gas just buying groceries," said Brad Huffman, a certified financial planner with Future Finances in Worthington.

What to do? Tune in next month when we talk about more ways to max out your gas discounts.

Denise Trowbridge is a self-professed money geek, who has written about personal finance, banking, and insurance for The Columbus Dispatch and Bankrate.com. She blogs about very personal money issues at middlepathfinance.com. Denise tries not to talk about money at cocktail parties, but sometimes she just can't help herself.