Right, but it's a 2-day study. You can't possibly reach any conclusions regarding the longevity of the components in the car to see what kind of affect the fuels may have. As Radar noted, running 91 in a 87 octane car prematurely ****ed out his Cat.

And my concern really isn't about 87 Octane cars running on 91, but rather 91 octane tuned cars running on 87.

So really, the article didn't do much to answer the question other than to let us know that 91 Octane doesn't really boost performance in an 87 octane car.....but that should be a bit of common sense. I found that out with my Firebird back when i was 19.

I'm not familiar with any potential damage that running 87 in a motor that "requires" 91 will cause. For me, it's a question of am I willing to spend another $0.30/gallon to not lose 20% performance reduction? My answer is yes.

Damn Donger. You pissed in my cheerios:( I have been using octane boost off and on for years.

Welp, learned my lesson. Thanks

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.

For me, Donger, it isn't about the performance of the car, but whether or not improper fuel can cause premature failure of components.

So with that said, I'll play it safe and pony up the extra 10-15 cents per Gallon.

Sorry, I thought that was understood. Yes, if running 87 in a 91 motor leads to pre-ignition, you absolutely want to switch back to 91.

I don't see why running lower octane would cause a timing chain/belt failure. But yes, interference engines are not much fun. I just replaced my belt because it's 14 years old but only 50,000 miles. The tech handed me the belt and just grimaced. No wear at all... LMAO But, I knew that if it goes, goodbye engine.

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

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.

I read this article the other day and found it helpful. If I had a vehicle that said "premium required", I wouldn't risk a lesser grade

http://www.edmunds.com/fuel-economy/...g-premium.html

Edmunds has compiled two lists: "premium recommended" and "premium required" for vehicles from the 2010-2015 model years (with some 2016 model-year vehicles). If your vehicle is on the "premium recommended" list, you're OK to try switching to regular unleaded gasoline. If, on the other hand, your car is on the "premium required" list, then you have to run premium fuel. You can confirm the information on these lists by checking your owner's manual.

"premium recommended"
http://static.ed.edmunds-media.com/u...ded.071515.pdf

"premium required"
http://static.ed.edmunds-media.com/u...red.071515.pdf

Sorry.

Yes, to an extent but that adjustment has to be within the parameters of what the engine can adjust for.
For most fuels available in the US I don't think it's a problem just stay far away from that E15 crap they're starting to push.

91 or 93 in my motorcycle and 87 sometimes 89 in all the cars except my Passat it takes diesel

Yep you ****ed those sensors, probably should get a harness also. They are cheap. You could do that job yourself easily. Add in the problem solver intake gaskets and that thing will last forever.

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?

Most stock tunes run a bit on the rich side for safety. You can get a chip that leans it out, giving you more power and better MPG. Just switching from 87 to 91/93 is not going to bump the power output up.

Cool. Thanks.

I did read in the manual that using the 91 would provide more performance, not sure how much.

So a new chip will make it more lean which provides more power AND mpg? I thought that there was a trade off between power and mpg. Up one and the other decreases etc.

Running a lead racing fuel will ruin cats too.

Knock and pinging is also known as pre ignition. Thats when the fuel is being ignited before the actual engine ignition process. The greater the octane fuel rating the greater its resistance to pre ignition.