Premium gas can be a waste of money

Many people use premium gasoline thinking that it’s better for engines than regular. That can be a costly misconception.

Regular gas typically has an octane rating of 87, while premium is rated at 91 to 93. But octane grades don't represent "good, better, best"; they simply measure a fuel's resistance to pre-ignition (pinging or knocking), a condition in which gasoline burns uncontrollably in the engine’s combustion chambers, possibly leading to engine damage. The higher the octane rating, the more resistance it provides.

Most engines are designed to run fine on regular gas. Using premium in them doesn’t improve performance; it only costs more money.

Even many cars for which premium is recommended can use regular gas without a problem. That’s because most modern engines can detect the presence of pre-ignition (which usually occurs under high-load conditions) and automatically make adjustments to eliminate it. The tradeoff when that happens is a slight decrease in power and gas mileage, but most people probably won’t notice it.

Generally, if your owner’s manual says "premium recommended," you can safely use regular gas.

Some engines do require premium gas. They’re typically more powerful ones used in sports and luxury cars. Those engines use a higher compression ratio, which can make them run hotter and make them more vulnerable to pinging. The high octane fuel helps them resist the condition. So if the manual says "premium required," follow it.

Learn how to save at the pump by visiting Consumer Reports’ guide to driving green. Check the latest national average gasoline prices.

Comments

[Stanton]

The tradeoff when that happens is a slight decrease in power and gas mileage, but most people probably won’t notice it.

Don't just gloss over this! Check it! I would like to see this tested and measured for a variety of cars!

You completely ignore that as gasoline prices have increased, the spread between premium and regular has remained the same. If premium really improves mileage for "premium recommended" cars, then that spread will eventually become less significant than the mileage gain.

Example:

A car (premium recommended) gets 25mpg with premium, 23mpg without. Premium costs $0.30 more.

At $3.00 / gallon for regular ($3.30 for premium), it costs $0.1304 per mile without premium and $0.1320 with premium. Not a good deal.

However, at $4.00 / gallon ($4.30 for premium), this changes. Now it costs $0.1739 per mile without premium and $0.172 with premium.

You do a disservice to your readers to not consider the effects of gas prices and the mileage gains "premium recommended" cars get from premium fuel. This effect only increases as fuel prices go up.

Please provide us with real numbers showing the value of premium gasoline and how it actually affects drivers at current gas prices.

[Ron]

Has anyone heard anything about the fuel pump problems on the 2007/2008 elantra's? I have heard about them shutting down during driving of the car

[Cale]

I often buy regular unleaded for my 04 Infiniti G35 even though premium fuel is recommended. Economy may drop as much as 1 mpg and there is really no economic advantage as David's analysis reveals. Yes, I'm filling up more often but I pay less per tankful. Maybe there's a psychological advantage.

[Dave Johansen]

The potential problem is even mentioned in the article ("The tradeoff when that happens is a slight decrease in power and gas mileage"), and it's claimed that "most people probably won’t notice it", but I'm not sure if that's actually the case.

For example, the current price for regular in Tucson, AZ is $3.759 and $3.919 for premium ( http://autos.msn.com/everyday/gasstations.aspx?zip=85701&vv=550 ). At that price, if you drive a car that gets 25 miles to the gallon with premium, then you're paying $0.15676 per mile driven. That means that your car needs to get more than 23.98 mpg with regular gasoline (calculated as "regular gasoline price per gallon / premium gasoline price per mile") for it to be a more cost effective purchase (excluding any additional wear that may happen on your car).

Basically, the minimal difference in cost will usually be eating up in reduced mpg or wear, so I wouldn't follow this advice.

[KimJSCP]

I drive a VW Passat and it is one of the vehicles that Consumer Reports says needs premium fuel.

I have found that using regular fuel causes a much more significant decrease in fuel economy than discussed above. I can't remember the exact numbers because it has been a long time since anything but premium has been in my car, but it more than negated any cost savings for the fuel. I believe that it was something like a 10% or more decrease.

Additionally, regular fuel greatly degrades the performance of my car and that alone make premium fuel worth it.

I can't imagine any reason I would ever put anything but premium in my car.

[Derrick G]

When the comment about the Elantra was first made, I checked the safercar.gov website and saw there indeed was an investigation going on. However, since the comment was so far off-topic, I didn't post anything at that time. However, realizing that new subscribers often go way back while poking around the site, I would now like to point out that the investigation has closed with Recall 08V429000 being issued on 65,000 MY 2008 Elantras to replace the fuel pump, so this shouldn't be an issue going forward once the recall work is completed. If anyone has had a similar problem with a 2007 Elantra, or any safety issue with any car, they still should report it via the safercar.gov site.

[Marty Cammarata]

I bought a new BMW 328xi Sport Wagon in December, 2007. The dealer insisted that premium fuel be used at all times, instructions I followed until I read the owners manual. On page # 113 under "Required Fuel" it states that BMW models 323i, 328i/xi can use 87 octane gasoline.
Luckily, I only used premium fuel for a few months. Happily, there have been no ill affects on mileage or performance with 87 octain fuel. Go figure.