Originally Posted by loochy (Post 11876746)

I think most modern cars have knock detectors that dial things back if excessive knock is detected.

Originally Posted by GloryDayz (Post 11876768)

Yeah, my 2002 Silverado has one that's pissing me off! Right after I cleaned the engine (t'was dirty as a power steering line had been leaking for a few months!!!), but ever since I get the knock sensor warning. I've read that it might be from the moisture I introduced while cleaning the engine, but it's been more than a month and I'm getting tired of resetting it.

And the fix seems like it has the potential to break as many things as replacing the sensor would alleviate.

But hey, it's a 2002, 250,000+ miles and I could not be more happy.

Originally Posted by Holladay (Post 11878330)

Just read my manual. On the CTS-V recommends 91 for better performance but can use 87. This darn thing has so much power, don't need anymore performance. My body can only take so many G's.

I am looking at trying to get better gas mileage thou. It would help if I could keep my foot off the pedal:) That said, averaging ~20 mpg, goosing it a bit when I want my cheeks to flatten. Would the 91 give better mpg? From what I have read, it would avg out...more money in the tank but longer on the road?

What about getting a "mpg" tune/chip? No more power, but max mpg?

Originally Posted by Radar Chief (Post 11876563)

Never heard of that one.
But I do know that running 91 octane in an 87 octane motor is sending more unburned fuel down the exhaust and can clog your cat(s). Saw that one for myself.

Originally Posted by Detoxing (Post 11876714)

But as the article noted, the car may start experiencing "knock" and if it does then you'd want to switch back to the appropriate fuel.

When i bought my Turbo Mazda i asked my business partner (A master fabricator/technician) if he thought the 91 Octane was required. His advice was to try it. If the car starts pinging louder than normal, then you need to switch back. Mine did, so i switched back.

My car is also known to have timing chain issues, which results in catastrophic engine failure. I have to wonder if those timing chain failures that people are reporting have anything to do with using improper fuel.