Is It Smart to Put Premium in Your Little Fortwo?

In spite of the rising gas prices, the price difference between grades of fuel has not really changed. I’d argue that the $0.10 difference to bump up a grade today is easier to take than the same $0.10 bump when gas was “only” $2 a gallon. Besides, you’ll be paying that same $0.10 extra next week for the cheap stuff, anyway, so if your car recommends the better grade, I say just buy it.
My xB gets 30 mpg in town and I drive 10k miles annually. Buying 89 octane makes it run better, and only costs me an extra $33 a year.

The Altima has a V6.
Today’s high compression ratios dictate the need for premium. Although the Cx-7 has moved from premium required to premium optional. Turbo and direct injection has led to the need for premium….and if you don’t, well just ask some of the Mazdaspeed6 owners who blew their warranty using 87.

P.S. From media.ford.com

The heart of every Mazda is its spirited powertrain. Under the hood of the CX-7 is a version of the turbocharged and intercooled 2.3-liter four-cylinder direct-injection gasoline engine, similar to that fitted to the MAZDASPEED3. Engineered to deliver high performance at all speeds, along with low exhaust emissions and excellent fuel economy, Mazda’s MZR 2.3 DISI (Direct Injection Spark Ignition) turbo-charged engine produces an enthusiastic 244 horsepower at 5,000 rpm in the CX-7. For 2008, the CX-7’s engine has been re-programmed and fitted with a new catalyst, making premium fuel now recommended, rather than required.

Among the people I know who have cars that recommend “premium fuel for optimal performance” (myself included) most scoff at the high price and put regular in instead.

Paul is correct that most modern cars (maybe models of the last 10 or so years) are not harmed byusing regular, regardless what they require or recommend, and are not even producing that annoying knocking if you use regular, because they have sophisticated computer software that can avoid it.

Despite that, I always put mid-grade (which is, surprisingly, the recommended fuel) in my “Magnificent 7″ 1998 BMW 740iL. Not worth risking making the engine unhappy and your friendly dealer or service station $1,000s richer.

With prices as high as $4.20 midgrade per gallon, the savings are miniscule, if you put $4.10 regular instead. A mere 2.5%?

You can save that by keeping your tires properly inflated. Or, if you underinflate by 20%, I just read your fuel efficiency drops by 10%!!!

You seem to have missed the point that the standard gas in Europe is 95 RON, which is equivalent to 90-91 (R+M)/2 in North America.
See for explanation: http://en.wikipedia.org/wiki/Octane_rating
All new European cars (small or large, family or sports) are optimized for 95 RON fuel, which explains why most of the cars mentioned are European.
In fact, the other grade available in European is 98 RON, which primarily destined for pre-leadless vehicles.
As mentioned by other commentators, modern cars (with their sophisticated engine electronic control units) will normally run on lower grades, but with less optimal fuel consumption.

Some years ago I read an article discussing the use of premium fuel. the key points of that article which included many discussions with engineers was the following:

1. your car engines knock sensor identifies the type of fuel you use and adjusts engine timing appropriately.

2. the use of regular in a car that requires premium will diminish performance by as much as 5%.

3. also, this will reduce milage by about 2%.

4. note - there are exceptions. For example, a car with a supercharger engine does not properly function on anything less than the required fuel.

First, thanks for adding the details, Bob. I think some of those numbers have changed, over the years, though the general drift of your comments is correct.

As to Graham, I understand your point about the difference in the fuels available between the two continents, but that is still largely irrelevant. We often criticize Detroit makers for not taking into account the needs of buyers in other markets. The same goes for the Europeans. A number of their vehicles HAVE been adapted to American regular, and while I would expect Mercedes to continue to require premium in larger models, ie an S550, or performance products, like an SL63, there is no reason a smaller-displacement C-Class can’t be adapted. Same with many VW products, etc. Incidentally, the list I posted the other day also includes a number of Japanese models, and there’s less an excuse for using premium there.
Paul

Although many cars that recommend premium can run fine on regular, typically they will not run as well and increase fuel consumption. The 2% you may save at the pump is lost with the 2% reduction in fuel economy. I have never been able to understand why this is even an issue. If the manufacturer recommends it then there are reasons for this recommendation. Turbos and higher efficiency engines require higher compression ratios and therefore higher octane. When purchasing a car make sure to ask about octane requirements so you know what is expected before buying the car.

What an idiot! Who cares if you have to spend 20 CENTS more per gallon! Let’s talk about apples to apples - Cost per person mile. Suppose two people in a Smart drive 100 miles round trip for a weekend trip. They use 2 1/2 gallons of gas, which would have cost $10.15 (June 7, 2008, $4.059 per gallon, assume 40 mpg hwy for the Smart). That works out to just about 10 cents per mile, or 5 cents per person mile. Now do that same trip with your new 4wd Escalade. It gets 18 mpg, and requires 5.55 gallons of gas to do the trip, costing $21.44, or 21 cents per mile; over 10 cents per person mile. You could achieve the same efficiency as the Smart if you ALWAYS drove 4 people in the Escalade; but in everyday usage you are more likely to fill the Smart to people capacity than you are to fill the Escalade all the time. Talk about carbon footprint!