AT today’s prices, it’s understandable that drivers accustomed to filling their gas tanks with premium would be looking for ways to ease the financial pain.
For premium-grade gas, prices to match.
Some relief may be as close as their next fill-up. Switching from premium-grade to regular unleaded can save several dollars on each tankful, given an average price difference of about 30 cents a gallon, according to end-of-July figures compiled by AAA.

While using gasoline that carried a lower octane rating than the engine required was once a sure path to disaster, that is no longer the case. Nearly all automobiles sold in the United States since the 1990s will happily run on regular-grade 87-octane gasoline without causing engine damage, a benefit of the electronic controls that now manage all engine functions.

The octane number posted on the pump is a measure of a gasoline blend’s resistance to a condition called knocking. The knocking sound — a rattling noise made by an engine under load, familiar to drivers of older cars — is a result of out-of-control combustion, the mixture of air and fuel burning erratically. The explosion rings the metal of the engine block like a bell.

The higher the octane rating, the more temperature and pressure the gasoline can withstand before it ignites on its own, rather than when it is set off by the spark plug. An engine that calls for premium gas typically has a higher compression ratio — it squeezes the air and fuel mixture to higher pressures — which can improve both fuel economy and power output. But such an engine requires the higher octane rating to run properly.

Before the switch to fuel injection and computerized controls, engines were subject to damage from prolonged knocking. But today’s engine management systems incorporate electronic knock sensors, which detect the condition and adjust the ignition to stop the problem. As a result, it is almost impossible to hurt a current engine by using 87-octane fuel, industry experts say.

“Modern engines prevent the damage from happening before it starts,” said Patrick Kelly, a fuels analyst with the American Petroleum Institute. “It wouldn’t impact fuel economy. And it wouldn’t impact the emissions. What it would impact is the performance.”

Of course, owners who do not heed the automakers’ recommendations may face consequences — the potential voiding of warranties, for instance. But for the most part, manufacturers’ fuel recommendations include some wiggle room.

Porsche, for example, acknowledges that any of its modern production cars can be run on regular fuel without the risk of damage.

A spokesman for Porsche North America, Tony Fouladpour, added a caveat. “If you want the car to perform at its maximum capability, the best choice would not be 87,” he said. “But we do not forbid it.”

Specifying premium fuel lets a car manufacturer squeeze out more horsepower. BMW, for example, recommends that all the cars it sells in the United States use premium fuel, but they will run on regular.

“There generally isn’t any harm done to the engine by using lower-octane fuel,” said a BMW spokesman, Thomas Plucinsky. “Because our engines do have very good forms of knock sensing and are able to deal with lower-octane fuels, you will not have any drivability issues. You will, however, lose some of the performance.”

How much of a loss? Some indication can be found in the peak horsepower numbers Hyundai recently released for its new Genesis sedan. On premium, the 4.6-liter V-8 engine is rated at 375 horsepower. On 87-octane regular, it is 368.

That seven-horsepower difference — less than 2 percent — seems a small penalty for saving 30 cents a gallon, especially when you can regain that performance simply by filling up with premium.

Does using lower-octane fuel reduce mileage or increase emissions, as some drivers believe? Not according to the Environmental Protection Agency. “E.P.A. fuels engineers say that there isn’t a meaningful difference between regular and premium gasoline,” said Dale Kemery, a spokesman for the agency.

Still, the warning from some automakers can give an owner pause at the pump. The manual for the Smart Fortwo repeats the warning issued for other vehicles sold by Mercedes-Benz: “To maintain the engine’s durability and performance, premium unleaded gasoline must be used.”

But even those stern words may have some room for interpretation. Dave Schembri, president of Smart USA, told John Schwartz, a reporter who was writing for this section’s blog about his experiences in buying a Smart, that he should not worry.

“You could use regular gas — there’s no damage to the car,” Mr. Schembri said.

Read the entire article here:http://www.nytimes.com/2008/08/03/automobiles/03OCTANE.html?no_inte...

Tags: Regular, gas, premium

Views: 26

Reply to This

Replies to This Discussion

All things considered, I would consider continuing to fill up with premium. The difference between regular and premium is typically 20 cents per gallon. With the eight gallon tank of a fortwo, that's a savings of $1.60 per tank.

The sticker on my Passion lists an average annual fuel cost of $1384 (15,000 miles, 36 mpg @ $3.32 per gallon.) Using the same formula with regular, priced at $3.02 per gallon, grants an average annual fuel consumption of $1258. So using regular saves you about $126 annually.

Is it worth it when you're dealing with a high performance 3-cylinder? When I can fill up the fortwo with premium for half of what it costs me to fill my minivan with regular, I'll say "YOU BETCHA!"

Roll 3d6
Glsson + Roll. I'm with you. What is this?

Mike why did you post this without back up info.? This, he told a blog writer for this forum Just does not get it. that's called hearsay.

If Dave Schembri did indeed speak for the record, and say it is not necessary that we use 91 octane in our cars, than this should come as an official release from Smartusa,

It's now time for Mr. Schembri to come forth on this site and clarify this issue.- A2Jack
The Schembri quote is quite clear - You "could" use regular without engine damage. Duh! Is that the criteria for which gas to use? It won't "damage" your engine? I agree that this question has been asked and answered too many times. Premium. (that's a "period" after Premium)
I do not endorse nor denounce this article, I simply made it available to the forum.
Mr. GLSONN I'm not debating this article with you or anyone else, and I certainly don't have to explain anything about it since it was written by the New York Times. However, on the other hand Smart USA and it's executives will need to further explain their conflicting positions. Furthermore each person is free to use any grade gasoline they wish. Next time please don't shot the messanger and then ask questions...please read the entire article as it contains full back up data. Thanks!
I just posted the entire article for those of you that could not find the web link at the bottom of the page.
Where is LeLapinBlanc when we need him? Im sure he could keep this going for days and evolve the topic into a conspiracy by smart in St Louis.
Mr. LeGLSONN, which part of "I'm not debating this article with you" did you not understand? I'm sure someone out there will be happy to explain it to you in full detail. Have a nice day!
This subject is being discussed on other Smart forums as well as here. Many new owners will jump right on the chance to burn cheaper gas. After all if the Pres. says it won't hurt anything, why pay more?

Did Mr Schembri just mis-speak ,or was he mis- quoted.

We now have 15k on our car and will hit + 30k before it snows. We need some real answers here...In the mean time we will burn 91+.

Our car is a NA451, 01-08 build, delivered in Feb. We run all our cars hard and fast, but take good care of them . Fuel represents a good part of our auto expenses. if we are wasting money here, we need to know... A2Jack
Permalink Reply by david douglas 3 hours ago
Where is LeLapinBlanc when we need him? Im sure he could keep this going for days and evolve the topic into a conspiracy by smart in St Louis.


Even he knows not to touch this one...
This thread is proof that some human beings will fight over anything. I for one am glad to know that if Smart ever sees fit to sell me one of their cars I can burn 87 octane without killing it.
Very "smart" info above. Thanks, Mike. B.J. at Smart Center Seattle said the car is tuned to look for 91 octane to achieve it's designed performance and if lower octane is used, no damage but will burn more fuel to achieve the design performance, result...no net gain....conflicts with your above statement - performance lost, but mpg the same. What say you?

Reply to Discussion

RSS

find a

smart center

go

Photos

Loading…
  • Add Photos
  • View All

Videos

  • Add Videos
  • View All

© 2014   Mercedes-Benz USA, LLC.

Badges  |  Report an Issue  |  Terms of Service