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If your car "requires" premium, I'd recommend sticking to it. With today's computerized ignition and fuel-delivery systems, late-model cars theoretically requiring premium can run on regular-grade by dialing back the ignition timing to prevent knocking... but it does that by actually detecting knocking first and then dialing back the ignition timing. While that's a lot better for the engine than having it knock all the time, it's still not good for it. Plus you'll lose a lot of power.
It actually burns cooler, higher compression engines have a hotter combustion, the higher octane burns slower. the slower burn allows higher comp. engine to run with out pre-detonation, Pinging.
If a car runs fine with no pinging on 87 octane you will not benifit from a higher octane.
I have the 3.9 liter v8 "AJ35" engine in my lincoln, which, according to the owner's manual, requires premium gas. i've never tried 87, but I get the impression it wouldn't work well in this type of DOHC setup. Jaguar AJ-V8 engine - Wikipedia, the free encyclopedia
I had a DOHC I-4 in my last truck. It required 87, but I found that the engine revved quicker and required slightly different timing on shifting gears when I used 93. Everybody told me that this wasn't the case, but I swear that premium made a difference. Toyota RZ engine - Wikipedia, the free encyclopedia
Some people will argue certain stations give better gas. okay, they can argue that. Proper, routine maintenance will make a far larger impact on your car's continued performance than the grade of gas you use.
there is positively a difference between brands. the difference isn't the gasoline so much as it is the additives/detergents in the gas.
original poster, your accord should be run on regular/87 octane as it was designed for it. to answer your question i'll expand off drover's answer: basically the higher the octane rating, the slower the fuel burns. if you have an engine that calls for high octane fuel but you use a lower octane instead because you think you're saving lots of money, the engine can compensate for it. but you lose power, which for you means the car runs like it needs a tune up. and what kind of mileage do rough running cars get? not so good. so now you've got a car that runs like hell with reduced mileage. and if you are getting worse mileage then you really didn't save much money huh...
We have Volvos. The owners manual recommends 89 or higher.
We use 91 octane in all of them.
This is the first car I have ever heard of that actually recommends the mid grade (89 OR plus). My grandparents have a 1999 Subaru Legacy Sedan and it called for 87. However, as it has gotten older, even with regular maintenance, the car has been flawless but I guess the carbon deposits on the engine have probably built up a bit and sometimes they used to get an engine knock or pinging so they switched to the mid grade and it ran smoother. I think cars today have the computer monitor engine performance and compensate for the different grade and as long as you don't beat on the car, short term, you should be ok. Usually this only is a factor if you are cheap and don't want to buy the premium, or if the gas station is out of the grade you use. My car recommends premium. I put premium. The car has a higher performance motor so that requires and needs the higher octane.
Its funny...aside from emissions, cars are relatively the same with engine requirments for most states (I would think). Octane rating is different depending on the state...I wonder if this gas burns differently for the emission standards. For example, here in FL and in NY, premium is 93 octane. When I was in Las Vegas, premium was 91 octane. That is only two octane ratings but there has to be a reason. They both were considered premium. Another time I was travelling and stopped right outside Cinncinnati, in Kentucky, and the gas station advertised a price I thought was 87. WHen I got there, it was called "Economy" and was an octane rating of "86". As far as I know, thats below the minimum requirement for any average car. Most cars require 87. I wonder what 86 would do if you consistently used it. And what benefit could it possibly be to make it? Its only 1 octane rating.
Please forgive me, I'm a little clueless about cars - I know about types of cars, but nothing about how they work. So here's the big mystery I've always wondered... does it really matter which kind of gas you use? I used to always fill with Premium, since that's what my gas cap said to use, but now I have a cheaper car & less money (not to mention Premium is $4/gallon here ). So I usually get Regular or Plus instead, and wonder if that makes a difference to my car? I mean mostly in terms of it's daily performance, but also for the long-term effects. I drive a 2005 Honda Accord LX, 4-cylinder, manual transmission... any suggestions or "dummy explanations" you can give me?
Simple answer, gizmo . . . whatever "the book" recommends.
Most modern engines are able to "compensate" for fuel differences but usually perform best (overall performance as well as fuel economy) on the octane recommended.
My father is a chemical engineer that graduated from MIT and recently retired after 30 years at Exxon/Mobil. He says only put inside your car what the owner's manual suggests to put. If the engine was designed to use 93 octane....then use it. If it was designed to use 87 regular...use that.
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So here's the big mystery I've always wondered... does it really matter which kind of gas you use? I used to always fill with Premium, since that's what my gas cap said to use, but now I have a cheaper car & less money (not to mention Premium is $4/gallon here 
). So I usually get Regular or Plus instead, and wonder if that makes a difference to my car? I mean mostly in terms of it's daily performance, but also for the long-term effects. I drive a 2005 Honda Accord LX, 4-cylinder, manual transmission... any suggestions or "dummy explanations" you can give me?
