With gas prices stubbornly staying above $3 per gallon, you owe it to yourself to find ways you can save on the cost of driving. If you haven't reviewed your car insurance in a while, you might be missing out on a wide range of valuable discounts.

The marketplace for auto insurance has become so competitive that new car insurance discounts are advertised all the time, says Michael Barry, a spokesman for the industry group the Insurance Information Institute.

Read on to see if you're getting all your entitled savings. Keep in mind that some auto policy price breaks may not be available in all states.

Save on Car Insurance Because of Your Work

You might be eligible for an insurance discount simply for doing your job.

Insurance companies keep tabs on which occupations tend to mean less driving, less risk-taking -- and thus, fewer accidents. If you're in one of those professions, you could enjoy savings.

Farmers Insurance Group provides discounts for members of certain occupations, including police officers, firefighters, doctors, dentists, registered nurses and teachers. Esurance offers its "preferred occupation" savings to certified educators, engineers and scientists.

Some employee car insurance discounts stem from business relationships. Geico gives a discount of up to 8% to workers at other subsidiaries of Warren Buffett's Berkshire Hathaway. Inc., including Fruit of the Loom and See's Candies.

If you're self-employed and working from home, you may still be eligible for a discount -- particularly if you rarely use your car. Most insurance companies cut the bill for "low mileage" customers.

Good Credit, Good Savings

Checked your credit score lately? The vast majority of insurance companies take credit scores into account these days, and a high one could help cut your auto premiums by as much as half, says insurance agent Sierra Knight, owner of KMI Solutions in Richmond, Va.

While most insurance companies won't divulge the formula they use to come up with what's known as a "financial stability discount," Knight says it's safe to say that someone with a score above 700 will be considered a better risk -- and eligible for lower payments -- than someone in the 500s.

Often, a financial stability discount will extend to all the policies you have with a particular insurer. Note that California and a few other states have banned credit scores from being used in determining car insurance premiums.

Serve Your Country, Get a Discount

If you're in the armed forces -- or are a college student taking part in a commissioning program such as ROTC -- you might be eligible for certain savings. Geico gives discounts of up to 15% for members of the military or National Guard, for example.

USAA, a financial services provider for people in the military, offers savings for those on active duty and says its premiums also reflect a customer's rank in the service. Plus, the company provides a 15% discount on the comprehensive portion of a car insurance policy if the vehicle is kept in a base garage. In some states, USAA gives an up to 80% discount for an active duty member who is deployed or otherwise away from home and places a vehicle in secure storage.

Membership Has its insurance Privileges

Were you in a fraternity or sorority in college? Your experience in Delta Delta Delta can come in handy for more than amusing your kids with your old pictures from the spring formal.

Through its affiliate program, Geico offers car insurance discounts of up to 8% in most states for members of an alpha-to-omega of fraternities and sororities. The same savings are available to people who belong to a long list of other Geico partner organizations, such as the South Carolina Bar Association, the National Society of Accountants and the Stanford University Alumni Association. Mercury Insurance and Liberty Mutual have similar programs.

It's not that Greek letters or club dues make you a better driver. Companies' affinity discounts might stem from sponsorship relationships. As "the official car insurance of the Pac-12 conference," Esurance offers discounts of up to 15% to students and alumni of Pac-12 schools who reside in Arizona, Colorado, Oregon and Utah.

Go Green and Save on Premiums

Reducing paper statements isn't just Earth-friendly. It cuts business costs. A few insurance companies, such as AIC, are passing the savings along by giving people who receive their statements by email a monthly discount, Knight says. Through its "e-sign" program, Progressive will immediately knock $50 off the price of an auto policy if you sign your documents online when you buy.

Most people know that if you reduce your mileage -- and thus your carbon footprint -- you'll see savings on your insurance bill. Some companies, such as Travelers, also offer discounts of up to 10% if you go green by driving a fuel-efficient hybrid vehicle. It's not that the hybrid cars are safer, insurance experts say; it's that the people who go out of their way to buy and drive them are seen as a better risk.

Lock Up Savings With Anti-Theft Discounts

You may already know the safety features that come with your car, such as air bags or anti-lock brakes, can reduce your premiums. But you might not have realized you can save money on the comprehensive portion of your insurance by installing anti-theft measures including: car alarms; fuel or ignition cutoff switches; stolen-car tracking systems such as LoJack; and VIN etchings, or engravings of your vehicle identification number on your windshield and windows.

A built-in system to deter thieves means a 25% reduction in the cost of Geico's comprehensive coverage. Allstate offers a 10% anti-theft discount on its premiums.

As you consider anti-theft devices, keep in mind that it pays to shop around. Some car dealers will charge you hundreds of dollars for VIN etching, for example, while membership organizations such as AAA occasionally provide the service for free. You can also buy VIN etching kits for $20 to $30.

Shop Around Early for Extra Savings

Planning ahead when it's time to renew your policy can put money in your pocket. Some insurance companies, such as Travelers Insurance and Allstate, give discounts of between 5% and 10% if you switch to them before your next premium is due. To take advantage of these early shop-around savings, you should start looking at least two weeks before your current auto policy is up.

But before you jump, there's one more call you should make. Ask your current provider if it will match the competitor's early switcher discount with a renewal discount. Chances are if you're a good customer with a stellar driving record, the insurer will match the deal in order to keep you, says Knight.

Some car insurance providers do reward loyalty. Nationwide gives customers who have been with the company at least five years a 15% discount, or 5% off if they've stuck around three years.

Get Discounts for Getting Educated

Got college students on your policy? Tell them to hit the books. Almost all insurance providers give some sort of good-grades discount for single, full-time students who are doing well in school and are under a certain age, usually 23 to 25. At Allstate, it's a savings of up to 20%.

"The data (show) that the better a student does in school, the less likely they are to have an accident," says Brad Hilliard, a spokesman for State Farm. While State Farm's "good student discount" varies depending on gender, age and marital status, it's usually in the range of between 10% and 25%, he says.

State Farm also has a special program known as Steer Clear that gives younger, student-age drivers an insurance discount of 15% in exchange for additional training and supervision, Hilliard says.

If you're well past your school years, you can get a car insurance discount if you go back to the classroom for a defensive driving course, also known as a motor vehicle accident prevention course. Organizations such as AARP offer the classes, or you might find a program through your state motor vehicles bureau.

1 + 1 = Deals for Couples

Two's company -- and it also means cheaper car insurance. Premiums can drop when you get married, as insurance company statistics show that drivers who are coupled up tend to be safer than those who are footloose and fancy-free.

Some insurers, such as Safeco and Travelers, extend those same price breaks to unmarried same-sex couples, says Knight. "It can afford them so much savings," she adds.

Other unmarried couples might insure their vehicles together to receive a multicar discount, which almost all providers offer. Or, if the two of you own property together and have homeowners insurance, there's usually a bundling discount to insure your car with the same company.

Whether you're married or single, do some research before you renew an auto policy to make sure you're getting all the discounts you can, says Barry, of the Insurance Information Institute.

"Look and see where you are getting discounts with your current policy," he says. "Are there discounts that other agencies are offering that you're not seeing? Ask them about it."

And while car insurance discounts are great, don't get carried away. The institute notes that a company that offers few discounts may still have a lower overall price.

Copyright 2012, Bankrate Inc.