When you top off your tank with five gallons of gas, you don’t pay the same amount as the retiree pumping 70 gallons into his top-of-the-line RV.

That would be crazy.

And yet, the two of you might pay the same amount for auto insurance if you’re the same age and drive the same make of car.

That’s true even if you live four minutes from work while she spends hours every day chauffeuring kids to band, swim and dance practices.

The ultracompetitive insurance industry has taken note of this disparity and seized it as a way to attract new customers. Several companies – including State Farm, GMAC, Progressive and Allstate – have introduced discounts for low-mileage drivers.

Signing up for a low-mileage discount isn’t as simple as making a quick call to your insurance agent, however. The plans available in Indiana come with some pretty big strings – and costs – attached.

Dick Luedke, State Farm spokesman, said insurance companies would go out of business quickly if they routinely underestimated the cost of insuring each client.

Policyholders can benefit if they’re on the low end of the warning scale.

“Our goal with each of our customers is to measure the risk as accurately as we can so we can charge the appropriate premium,” he said. “In general, the fewer miles you drive, the less likely you are to be in an accident and the less likely you are to file a claim.”

State Farm and GMAC offer discounts to Indiana policyholders who don’t drive much. The others haven’t introduced their programs here.

Insurance, unlike most industries, is regulated by individual states rather than the federal government. As a result, insurers introduce new programs slowly, making sure they are profitable and popular before spending time and energy to negotiate the rules established by additional states.

Roxann Carpenter, who has a Motors Mutual policy on her 2001 Chevrolet Cavalier, is confident she could save money with a low-mileage insurance program.

The Fort Wayne woman has a modest commute: five miles each way.

“It’s kind of like health insurance,” Carpenter said. “They should give rebates to non-smokers and people who get annual checkups.”

Now that she knows such discounts are available, Carpenter has another item for her to-do list.

“I should shop around,” she said. “I should make it a priority.”

But the discount programs aren’t for everyone.

Mason McCulloch isn’t interested.

“I guess I don’t shop too much for that kind of stuff,” he said.

The 80-year-old Fort Wayne man has had policies through The Hartford for years. That’s the insurer for his 2006 Ford Escape and 1999 Honda Acura. McCulloch believes the premiums he pays are reasonably priced.

“I don’t have any wrecks, I guess,” he added.

Reggie Wilburn, funeral director, lives less than five miles from Ellis Funeral Home.

He already receives a discount because his premium rates are based, in part, on his annual mileage. Wilburn, who has been with the same company for 17 years, isn’t interested in switching insurers now.

State Farm offers three versions of its Drive Safe & Save program, but only one is available to Hoosier drivers.

To participate, policyholders must have the OnStar device installed on the vehicle and pay a monthly fee for the service. GMAC Insurance’s low-mileage discount program carries the same requirement.

OnStar, a wholly owned subsidiary of General Motors Co., was initially available only on GM-made vehicles. The navigation and safety device allows drivers to request voice-activated phone calls, turn-by-turn directions, roadside assistance and emergency assistance after a crash.

As of 2011, about 6 million people subscribed to the service.

Last year the company introduced a version called OnStar FMV (For My Vehicle), which can be installed in many other automakers’ cars, trucks and SUVs.

Retail price for the system is $299. The device – including installation – has been offered for as little as $99.99 on sale.

That’s the first step. The monthly service fee is the next.

OnStar FMV subscriptions start at $18.95 a month or $199 a year for the Safe & Sound package. Directions and hands-free calling costs more.

Anyone who bought OnStar service just to save on auto insurance would need to save a minimum of $300 on premiums the first year to offset the startup costs.

With GMAC’s program, if your annual premium was $800, you’d have to drive less than 2,501 miles a year to save more than $314.

Luedke, the State Farm spokesman, said anyone enrolling in the insurer’s Drive Safe & Save program receives a 5 percent premium discount the first six months. After that, savings are based on the number of miles driven the previous policy period, as recorded by OnStar.

Average savings are 10 percent but can climb to almost 50 percent off regular premium prices for people who rarely use their cars, Luedke said.

State Farm offers two other low-mileage programs. One works with Ford’s Sync system instead of OnStar. And the other works with the In-Drive system.

The company spokesman anticipates both programs eventually will be offered in Indiana.

Drive Safe & Save with In-Drive allows good drivers to get discounts because the device tracks driving habits, including acceleration and deceleration rates, speed during turns and speeds exceeding 80 mph.

For competitive reasons, Luedke isn’t allowed to say how many of State Farm’s Indiana customers – or policyholders nationwide – have signed up for the OnStar-based savings program. The insurance provider first rolled out the program in Ohio in 2009.

“But we feel very good about the response so far,” he said.

GMAC’s website says the insurer has more than 30,000 policyholders enrolled in its low-mileage discount program.

Low-mileage discount programs were first introduced in 2011 but really gained popularity this year, said Alex Matjanec, co-founder of MyBankTracker.com. The New York-based company educates consumers about banking, finances and insurance.

The website’s revenue comes primarily from display advertising.

Progressive Insurance, which gives discounts based on how people drive, has been the most aggressive in advertising its SnapShot device discount. The company reported 500,000 participants in the program this year. Of them, 70 percent save at least 30 percent on premiums as a result.

Low-mileage discounts are good for retirees, people who live close to work and those who work at home, Matjanec said.

If you have a long commute, “this program is definitely not for you,” he said.

Researchers have estimated two-thirds of U.S. consumers would benefit from such a discount, according to a study published by The Brookings Institutions in 2008.

Savings could total $270 a car, on average, wrote Jason E. Bordoff and Pascal J. Noel, authors of “Pay-As-You-Drive Auto Insurance: A Simple Way to Reduce Driving-Related harms and Increase Equity.”

The authors estimate driving would decline by 8 percent if consumers had added incentive to limit their miles. What’s more, they said, it’s just not fair.

“This pricing system is inequitable because low-mileage drivers subsidize insurance costs for high-mileage drivers, and low-income people driver fewer miles on average,” the report states.

Ultimately, several factors affect auto insurance premiums. Some factors – such as age and city – aren’t easily changed.

But anyone who signs up for a low-mileage program can monitor his odometer and choose to bike, walk or carpool if he’s getting close to exceeding a given cutoff mileage amount, State Farm’s Luedke said.

“It gives the customer some control,” he said, “over how much you pay in insurance premiums.”

sslater@jg.net