SAN DIEGO (CBS 8) - You're saving money, but could it cost you in the long run? We asked if there's any difference with the same grade of gas sold at different locations and prices.

Ever wonder if the 87 octane fuel you put in your car at less expensive gas stations is the same quality as the 87 octane fuel you buy at some of the brand name stations that charge you a few pennies higher per gallon? The County of San Diego Department of Agriculture, Weights and Measures say rest assured.

Deputy Agricultural Commissioner James Byers says some stations tout additives that will improve your car's performances, but he says most of the gasoline we buy comes from the same source.

"Most of it comes from the same refineries through pipelines, then they end up in the storage racks in Mission Valley," Byers said. "It is the same gasoline at the loading racks, just with the different additives."

So the next question is, should you pay more for those additives? The Automobile Club of Southern California says it's not necessary.

"We actually did a scientific study comparing emissions, fuel economy, drivability and performance of half a dozen blind samples of different fuels, and they were all exactly the same. We could not tell any difference whatsoever," Byers said. "The bottom line is the quality of even the least expensive gas, is as good as the most expensive gas."

That's not to say mistakes aren't made. There have been cases where regular unleaded has been placed in premium pumps, for instance. Drivers can report issues to the county.

"The only time they need to worry is if they start to drive off and their engine starts to perform worse or they hear a pinging in their engines or valves. Then they can call us and we'll certainly go out and take a sample of the gasoline," Byers said.

If you have a concern or complaint, you'll find a number to call on the pump's certification seal. In San Diego County, it's (888) 878-3722.

The Department of Agriculture, Weights and Measures tests and certifies each of the 19,000 to 20,000 pumps each year, and the state does random testing as well.

The Auto Club's automotive research manager also advises people to read their owner's manual. If it says "premium 'recommended,'" he says you won't hurt your car at all if you use regular unleaded. He says you only need to use premium if your manual says it's required.