it seems everyone on here just "guesses" they need or dont need certain fuels.
did a little searching and found a nice article:
http://www.us3s.org/freeforum/showthread.php?t=5205.
Ford uses "recommended" now just as they did in 1993, for maximum engine power premium is "recommended" not "required".
kinda like drinking 8 full glasses of water a day is recommended, but not required.
me? i use premium for best performance,not because i fear engine damage from it.
My old turbocoupe ran on 23psi of boost after i installed the t4 turbo, so i was "required" to use premium, it would detonate like hell if i didnt.
Experts knock premium
Pricey gasoline doesn't benefit most kinds of automobiles
April 3, 2003
BY MARK PHELAN
DETROIT FREE PRESS BUSINESS WRITER
What difference does it make if you use regular or premium gasoline in your car?
About 20 cents a gallon.
It may be small comfort with gas prices remaining so high, but you virtually never gain anything by running a higher and more expensive grade of fuel than the manufacturer recommended, and you may not lose much if you use a lower grade of fuel, a variety of experts say.
A lot of people fill up with premium every third or fourth tank. Some do it to clean out the engine, some to get a little more power or help an older engine run smoothly.
It's a nice idea, but they might as well toss 20 cents a gallon into a wishing well.
"It's a waste of money," said Harold Schock, professor of mechanical engineering and director of Michigan State University's Automotive Research Experiment Station, which studies combustion systems.
"It doesn't make any difference for most people," Schock said. "Most engines are designed to operate on relatively low-octane fuel."
There is no power difference from high-octane premium to low-octane regular, said Robert Furey, a fuel specialist with General Motors Corp.
"Octane is simply a fuel's resistance to knocking," he said.
"There's no benefit if the octane is higher than the engine needs, but if it's too low, that can cause knocking," he said.
Engine knock -- what happens when fuel in a combustion chamber ignites before it should, causing a disruption in the engine's operation -- used to be a major concern, but devices called knock sensors have nearly eliminated it, said Pete Dowding, manager of Ford's modular V8 and V10 engine program.
Before electronic knock sensors became common, a bad tank of fuel could be disastrous, because persistent, severe knocking can destroy an engine, Furey said.
"If you find your car runs fine on a lower grade of fuel, go ahead," said Bill Hickman, spokesman for the American Petroleum Institute. "We don't encourage people to buy a higher grade. Just follow the manufacturer's suggestions."
Some automakers still say premium is required for their high-performance engines, but even they admit it's more of a suggestion than a command.
"Based on our high compression ratios, it's important to use premium," said Rob Mitchell, spokesman for BMW of North America.
"However, you can run on regular if no premium is available. We don't recommend it, but it won't damage the engine. There is a slight deterioration of performance, however."
Running regular fuel in an engine designed to use premium does reduce performance and fuel economy, Furey said, but too slightly for most drivers to notice.
GM requires premium for just two engines: its supercharged 3.8-liter V6, used in the V6 Buick Regal GS, and high-output 1.8-liter four-cylinder in the Pontiac Vibe GT.
Even the Chevrolet Corvette runs fine on regular, Furey said, although GM recommends premium for maximum performance.
On the other hand, some engines have sophisticated two-way knock sensors, which allow them to generate more power if you use a higher-octane fuel than the manufacturer recommends. Chrysler reportedly fits some of its engines with such sensors, meaning that a fill-up with premium actually can put a tiger in your tank.
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