Switching from premium to regular may do damage

With premium gas costing drivers 65 cents more per gallon on average than regular gas as of Tuesday, drivers may be tempted to fill their tanks with regular fuel to save money.

But is it a good idea?

Experts say the right fuel choice will depend on what kind of vehicle you drive. If your car requires premium gas, switching to regular can help lower costs at the pump but could also lead to expensive repairs down the road.

“If I had a car that required (premium gas) and there was a huge gap in price and I’m going on a road trip, you could probably get away with it,” said Jason MacDonald, director of operations at Village Ford, a dealer in Michigan. “But I wouldn’t risk it.”

What’s the difference between regular, midgrade and premium?

Most fuel stations sell three types of gas: regular, midgrade and premium. Some stations have different names for each grade – such as unleaded, super, extra, supreme or super premium – but they all refer to the different levels of octane.

Typically, regular fuel has an octane rating of 87. Midgrade, a mix of regular fuel and premium fuel, has a rating of 89 or 90 while premium is somewhere between 91 and 94, according to the U.S. Energy Information Administration. Ratings differ slightly from state to state.

“That may seem like a foreign number to some people, but what it really means is the ability of the gasoline to resist detonation or exploding before it’s supposed to,” Greg Brannon, director of automotive engineering at AAA, told USA TODAY.

Put simply, higher octane ratings mean the fuel is more stable, which is a necessity for certain engines.

“If the octane isn’t high enough for the particular situation, the fuel will light itself because it gets hot, and what that does is causes either spark knock or detonation. And that’s really bad for your engine,” Brannon said.

Can I use regular gas if my car requires premium?

Experts advised against switching to regular gas if a vehicle requires premium.

If a vehicle requires high-octane gas but is filled with lower-octane gas, drivers risk damaging the powertrain, which includes the engine, transmission and other components, MacDonald said. Damage to the powertrain could cost $20,000 to $30,000 in repairs to the engine plus labor costs, he said.

Brannon noted that most cars are equipped with sensors that can help certain vehicles run on lower-octane gas even if they’re built for premium gas, but switching gas can still cause damage.

“It’s really not a good idea,” he said. “The engine may not be able to adjust (to regular gas).”

Brannon added that drivers who use regular gas in a vehicle that requires premium could void their warranty.

Drivers can find out what kind of gas their vehicle requires by looking at the owners’ manual or their gas tank door. Brannon estimates roughly 75% of cars on the road take regular.

If premium gas is recommended, can I fill up with regular gas?

But what should drivers do when they’re told premium gas is recommended but not required?

Brannon said AAA research has found there are “very, very small differences” in performance and fuel economy when these vehicles use the recommended premium versus lower-octane gas.

“When a car recommends premium, you might only get one or two percentage points better fuel economy and horsepower if you use premium fuel over regular,” Brannon said.

With gas prices up, he recommends these drivers use regular gas “in the vast majority of cases.” Certain circumstances, such as pulling a heavy load, may make premium gas worth the higher cost.

Which vehicles require premium gas?

Fuel requirements vary from vehicle to vehicle, but Brannon said premium fuel requirements are more common among sports cars, luxury sedans with high horsepower engines and engines that have turbochargers.

“A luxury brand is not all that concerned with the cost of ownership because the vehicle itself is very expensive,” he said. “They’re trying to get the most performance out of that car. If they have to require their customers use premium, that’s fine. Their customers understand that and hopefully continue to do that.”

At Village Ford, President Jim Seavitt said most Ford vehicles require regular gasoline and only high-performance Mustangs use premium.

“I’ve got a Mustang Shelby that has to use premium. If it’s a high-performance vehicle then it uses premium and people who buy a high-performance car expect to put premium in it,” Seavitt said.

Should I use premium gas instead of regular gas if it’s not required?

Some drivers put premium gas in cars that run on regular gas, hoping for better performance. But Brannon said doing so is a waste of money.

“It is literally going out the tailpipe with absolutely no benefit to you as the consumer,” Brannon said.

In search of higher grades of gasoline? Brannon recommends searching for stations that offer “top-tier” gasoline, which meets certain standards for enhanced detergent additives and can keep engines cleaner.

The AAA recommends drivers look for a top-tier fuel that is the correct grade for their vehicle.

“It’s easy to get confused because of all the marketing that’s done around premium fuel,” Brannon said. But toptier gas “will actually keep the engine running longer, happier, (with) better fuel economy and the like.”

He added that top-tier fuel prices are “comparable” to other prices. Drivers looking for top-tier stations can search online at www.toptiergas.com/.