: octane gas



nascarhead
03-04-10, 02:16 PM
i just purchased a used 2007 STS-V and i was wondering if it is truely required to have the premium gas in it. and if it is, would the check engine light be triggered if i put in regular 87 octane gas?

dhemrick
03-04-10, 02:42 PM
Yes, they require 93 octane. Do NOT put 87 octane in it.

jedhead
03-04-10, 02:43 PM
I don't know about the check engine light, however you can get holes punched in the pistons if the PCM can't take out enough engine timing to prevent severe detonation. Other cars that I have owned that can run on regular have labels saying premium recommended. The STS-V has labels that say premium required. ~$3.50 a tank savings is not worth the risk of damaging the engine in my opinion.

Bob

nascarhead
03-04-10, 04:59 PM
thanks guys... will follow your instructions. high octane it is.

csf
03-04-10, 07:46 PM
What a coincidence you posted this question. Two weeks ago I was forced to put 87 octane in my STS-V. I live in Baltimore, we had just had 45" of snow in one week, my STS-V was on nearly on empty, and the two closest gas stations were completely out of gas since no trucks had been able to make any deliveries. But one Shell station about two miles away still had gas, but only 87 regular. I had no choice so I put in $20.00. I was not happy.

Bottom line is the car seemed to run the same - no knocking, pinging, or lesser performance in normal driving. Gas mileage, which I always reset when I get gas, went from my normal 15 - 16 mpg to 17.6 mpg for the same basic driving.

Make no mistake, I put premium in as soon as I could and continue to do so. But that $20.00 of regular did not trigger any Check Engine Light or other bad behavoir that I could feel or see.

Red Snake
03-05-10, 11:51 AM
Since you got better gas mileage and had a lot of snow, I would have to assume that you drove conservatively with the 87 Octane in your tank. That worked in your favor.

Where the lower octane would be an issue is at WOT. That's where the vehicles tune is at it's most optimum and runs "lean" for maximum performance.

You were fortunate. Had you made some WOT blasts with the lower octane in there, you would have been MUCH more likely to have encountered detonation, especially in the cool or cold air (which results in an even "leaner" burn than normal). Good move to go back to 93 octane at first chance.

You got by with the lower octane due to the circumstances. Getting detonation on a supercharged engine is no joke. You can seriously grenade the motor in a heartbeat. Sometimes you can get away with things. It's that one time that it bites you that sucks.

CIWS
03-05-10, 04:14 PM
From the owner's manual.

"If your vehicle has the 4.4L V8 engine (VIN Code D),
use premium unleaded gasoline with a posted
octane rating of 91 or higher. For best performance, use
premium unleaded gasoline with a posted octane
rating of 93. In an emergency, you can use regular
unleaded gasoline with an octane rating of 87 or higher.
If 87 octane fuel is used, do not perform any aggressive
driving maneuvers such as wide open throttle
applications. You may also hear audible spark knock
during acceleration. Refill your tank with premium fuel as
soon as possible to avoid damaging your engine. If
you are using gasoline rated at 91 octane or higher and
you hear heavy knocking, your engine needs service."

csf
03-06-10, 12:44 PM
Since you got better gas mileage and had a lot of snow, I would have to assume that you drove conservatively with the 87 Octane in your tank. That worked in your favor.

Where the lower octane would be an issue is at WOT. That's where the vehicles tune is at it's most optimum and runs "lean" for maximum performance.

You were fortunate. Had you made some WOT blasts with the lower octane in there, you would have been MUCH more likely to have encountered detonation, especially in the cool or cold air (which results in an even "leaner" burn than normal). Good move to go back to 93 octane at first chance.

You got by with the lower octane due to the circumstances. Getting detonation on a supercharged engine is no joke. You can seriously grenade the motor in a heartbeat. Sometimes you can get away with things. It's that one time that it bites you that sucks.

Conservatively would be an understatement. Except for the highways which were pretty clear, local traffic was mostly bumper to bumper due to the huge snow banks taking away the outer lanes. Avg MPH for that $20.00 was 17.2 mph. Its now full of 93 again, which is still under $3.00/gal here.

On a side note, almost never drive WOT anymore. I just have more fun shifting the tranny - which I seem to do everytime I drive the car.