August 3, 2008
New York Times Motoring
Premium Required? Not Necessarily

By DEXTER FORD
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.
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.

 

Here's my thinking, the automotive industry will tell you that the motor will run on cheaper gas. In essence they are telling the truth, it will. But what damage will the cheap stuff do to that motor. The giants want you to run that crap gas, because when your motor fails prematurely, what do you do? In our case, the car is no longer made, and the engine is valued @ what?? Something like 12,000$ And the SRT guys are even more? Do you replace it or get a new one (or another one)?? Auto industry makes money hand over fist because of people not taking care of their vehicles...


Justin

 

Very interesting read and not far from what I expected. For me, my filling station only charges .10 more per gallon, so I don't think it overly beneficial for me to "risk" it. I can certainly understand those who will, but I agree with Jeep2Xfire.

Quick story when I was buying mine, the salesmen said you don't have to run premium, you can go with regular. When I call a couple of maint shops, including the dealership I was buying from, the maint folks said you'll experience performance issues and will get the check engine light after a while.

 

I will just reiterate what more than one person on this forum has already stated.....it's a SPORTS CAR !
And I'm sure there'll be some argument about that statement also, but for me, I'll retain my measley " 7 " horsies thank you !!! " Premium Gas Only "

Just my Dos Centavos

 

I'm sure not going to take the risk. 15 lbs of boost w/reg gas sounds like a bad idea.

 

Forced induction cars running on regular? Thanks, but no thanks. Cars would definitely run much better on the premium fuels in this case. I tried it one time on my turbo GTI and got crazy ars detonation at wide open throttle, especially in the heat. No way am I gambling on my high performance SRT.

 

Oh, I'm sure you CAN run regular but, as other members have pointed out in the past, you're timing gets retarded by the anti-knock sensors & zip, there goes your power.
I'll pony-up the few extra pennies & be assured I still have the "go" when I need it!

 

On 10 gallons of gas we're talking about $3.00/week or $150 a year. Hell, if you want to save money on gas don't floor the car from every stoplight and you'll save a lot more than $3.00 a week.

 

I posted the article for information only not an endorsement

 

Completely understood, Nightrider! We're just teeing off on the whole idea.

 

I have run 3 Audi's on 87 Octane - no issues. the crossfire - I'll keep putting the good stuff in - I fill the tank once every 2 to 3 weeks - so what am I going to save - isn't going to get me a vacation in Hawaii or even the Jersey shore. Good read - and I believe it wouldn't hurt the car.
Never killed the Audi's and we are on our 4th.

 

A bit off the topic, but maybe not. Does anyone know about the E-85 gas that is showing up at the stations? I think I remember that someone here had converted a Crossfire to E-85. If so, how is that working?

 

I was told that putting regular in your Crossfire will void your warranty. Although I doubt that they will be able to tell, mayby by the damage. Additionally to the loss of power, regular can leave deposits on the valves that the higher temperature premium will burn off, again prolonging the life of the motor. I put premium exclusively in mine, except for approx 1 gal of regular that I accidentally pumped before my wife stopped me - LOL.

 

I though "Regular" fuel burned at a higher temp. than premium. I thought that's why if you use reg. in an engine that needs premium, it will eventually burn a hole into the top of your piston.

 

I am not a mechanic or a chemist, and I didn't stay in a Holiday in Express last night, but I beleive that you have it backwards.

 

Actually, I don't think they burn at a significantly different temp. at all. It's just that Premium has a higher "ignition" temp. than reg. does.

 

Thanks for the article.. It fims up what the mechanics I've been talking too have said. Less performance, not great for those of you that want to run with your hair on fire, but the computer does take care of the knocking problem.
I'm sure the oil companies love to sell that premium gasoline, but then there is a sucker born every second I've heard. I try to use good sense and run premium if I'm going to push the car hard, but around town I really don't see the difference even in the mileage improvement that I'm sure is supposed to happen if you run premium.

 

I've seen the way YOU drive! You should be running Premium fuel at ALL times!

 

First I have to say I bought a SPORTS CAR not an economy car. For a sports car our cars get good fuel economy but anyone who purchased a sports car expecting fuel economy probably didn't think things all the way through. I did run a test with two tanks on regular once and found a noticeable drop in performance and MPG despite what the article states. I have since had my ECU remapped and tuned for 93 and I have not used regular since.
I say use PREMIUM. JMHO

This message was approved by by me but I have since decided I must withdraw that approval !

 

It has more to do with compression and the ability to with stand self ignition based on that compression. Overall, regular gas will self ignite at a lower compression than premium, hence it cause premature ignition. This results in the "knocking" that you hear sometimes in high compression engines thats running on reg fuel. This can cause damage to the engine components. And for those that say the oil companies rather sell premium..that is not always true.