Your OnStar service can help you out of jams – locked keys in the car, roadside breakdowns, etc. – and it can help cut your auto insurance bill.

GMAC offers its customers in 34 states with OnStar subscriptions a break on their bill of 26 percent and more when the service shows they drive less than 10,000 miles a year.

Progressive is another insurer offering discounts to drivers who willingly record their odometer readings with a GPS. And with Safeco’s Teensurance, parents can program a GPS unit to send an e-mail when the teen’s car violates certain conditions, such as driving beyond the speed limit or driving too far from home. Safeco plans to offer users a 5 to 15 percent discount on insurance

Best Buy stores have also seen an uptick in customers asking for GPS navigation systems, says a spokesperson, in part because of their potential to cut insurance costs.

In general, GPS car systems are a winner. They help you plan direct driving routes, avoid traffic jams and help you locate the cheapest-priced gas station nearest wherever you are. Among the brands ranked highest by Consumer Reports are Garmin, TomTom and Magellan. Cost: $100 and up.