I think you are right about the knock sensor TheJazz. I ran across a good USA Today article on the subject of which gas to use. Bottom line for me is that I drive 100 miles per day round trip to work. I don't care about the slight loss of power as much as I care about the dent in my wallet when using premium.

Here are a few of the highlights. Check out the link for the full story........

Prejudice and preference aside, engineers, scientists and the federal government say there's little need for premium.

"I personally use regular even though my owner's manual says you'll get better performance with premium," says Lewis Gibbs, consulting engineer and 45-year veteran at Chevron oil company. He's chairman of Technical Committee 7 on Fuels, part of the Society of Automotive Engineers (SAE) Fuels & Lubricants Council. Gibbs knows gas.

"My wife runs midgrade (89 octane) in her car, and it's a turbocharged engine" meant for 91-octane premium, he says.

The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell.

Automakers say they don't test premium engines on regular to check the difference, but some auto engineers estimate that power declines roughly 5%.

Today's engines use highly evolved versions of a device called a knock sensor to adjust settings automatically for low-octane gas. And more engine control computers have adequate memory to allow separate sets of instructions for various octanes. The engine control computers keep pushing to maximize performance on whatever grade of fuel is used.

Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey.

http://www.usatoday.com/money/autos/...emiumgas_x.htm

 

Very cool article.

I usually run 89 for two tankfuls a month, then 93 for the third. Why? Because I'm CRAZYYYY!!!