87 octane gas mistake

[kj973]

Originally Posted by Nychus

BACKFIRE? DETONATION?

prove it. fill the tank again,. and video tape it. post it on youtube.

Im curious myself

[Barry]

I wish i knew where the article is but it was in the Porsche owners mag that my dad gets it was a whole group of 911 owners in Texas or something that only ran 87 in their cars. They never had a problem. With out 11 to 1 compression i worry a little but honestly your not gonna hurt anything. You have a factory knock sensor and a pretty complex ecu its gonna pull timing when it senses knock thats what it is there for. I am not saying i am gonna go out and switch to 87. There is another school of thought that states 87 is less refined and has more "stuff" in it personally i think thats bs but what do i know.

[sh33t_0f_p4p3r]

youll be fine, just dont get on it and drive llike a grandma

[Dar-Dar]

i always put 93 in my FG2. but one day (since i live in NJ and its illegal to pump your own gas), i asked the gas pump guy to fill me up with 93. when i received my reciept, it said that i filled up my car w/ 87(i wasnt paying attention to the gas pump). i was pissed off cuz its 5% 93 and 95% 87, but nothing happened to my car.

-so what im trying to say is that your car will be fine and you cant trust gasoline stations in NJ.

[blacksi2007]

its not that serious..........my girlfriend filled mine up with regular one time and guess what? Nothing bad happened!

[jameslewis178]

you guys are over dramatic. it doesnt detonate and it doesnt backfire because you use 87 octane. maybe if you were making alot of power n/a or f/i it would but your car is fine. it may ping some at first but our computers are to smart and fix everything on there own. and higher octane gas does get better gas mileage

[Barry]

Originally Posted by jameslewis178

you guys are over dramatic. it doesnt detonate and it doesnt backfire because you use 87 octane. maybe if you were making alot of power n/a or f/i it would but your car is fine.

Do you know anything about octane? Cause it seems like you are just saying that.

[mrbill]

Originally Posted by Your Owner's Manual

Fuel Recommendation
All models except Si
Your vehicle is designed to operate on unleaded gasoline with a pump octane number of 87 or higher. Use of a lower octane gasoline can cause a persistent, heavy, metallic rapping noise that can lead to engine damage.

Si Model Only
Your vehicle is designed to operate on premium unleaded gasoline with a pump octane of 91 or higher. Use of a lower octane gasoline can cause occasional metallic knocking noises in the engine and will result in decreased engine performance. Use of a gasoline with a pump octane less than 87 can lead to engine damage.

To summarize.
For the R18, use of lower than 87 octane can damage your engine.
For the K20Z3:

• Use of lower than 87 octane can damage your engine.
• Use of greater than or equal to 87 octane and less than 91 octane can decrease performance (and cause an occasional knock).

The owner's manual doesn't give a fuel recommendation for modified cars.

-mr. bill

[Barry]

For people who don't think lower octane isn't more prone to knocking or pre detonation you should probably read into what the octane rating mean "Octane ratings are ratings used to represent the anti-knock performance of petroleum-based fuels (octane is less likely to prematurely combust under pressure than heptane), given as the percentage of 2,2,4-trimethylpentane in an 2,2,4-trimethylpentane / n-heptane mixture that would have the same performance. It is an important constituent of gasoline." -wikipedia is your friend.

[klutzyfool]

Originally Posted by msjwild3

The owners manual recommends 91 but no lower then 87.
87 is going to do no harm to your engine, otherwise Honda wouldn't tell you it is okay.

http://techinfo.honda.com/rjanisis/p...606O00180A.pdf


Exactly. Let's just all follow the owner's manual, and move onto other, more interesting topics.

[KraziAzn]

Originally Posted by dwm5f5

Okay...so I knew the moment I bought this car that this would happen eventually. I wasn't paying attention at the pump today and I put about $10 worth (@ 2.99/gal) of 87 octane in. Before this, I had 1 bar of 91 in. I immediately put $20 (@ 3.34/gal) of 93 in. I babied it around town for awhile and no detonation/cel/knocking/pinging/etc. I refuse to do the math right now, but that's around 35% 87 and 65% 93. (not counting the bar of 91)

I plan on babying it for awhile and keep filling up with 93...but has anyone experienced knocking with this low of octane?

I'm extremely hesitant to put any kind of fuel additive octane booster in my baby, but if any knowledgeable person can convince me otherwise....(ps, that will take A LOT of convincing)

And just to make me feel better, has anyone else done this??

wtfffffffffffffffffffffffffffffffffffff! 2.99 for 87? omg and 3.34 for 93??

dude where i live its like 3.54 for 87 and like 3.78ish for 93

lucky u

[OhondaU]

Higher octanes have a higher self ignition temperature, which has been thoroughly (enough) discussed here.

Modern ECUs have knock detection which 95% or so of the time will detect the onset of pre-ignition (knock) and retard the ignition timing to prevent it. Under most daily driving circumstances, even the spirited onramp jaunt, most people won't be able to tell the difference. If you do notice the difference or race your vehicle on a regular basis, then feel free to put 91 or better in your tank.

Its a personal choice based on your circumstances, experience, and feelings on the matter. Either way, your engine will be fine.

P.S. we all know the real fun is in the corners anyway, so why worry about the engine

[vtecmike1]

just because our knock sensor will retard timing to prevent damage while you run 87 doesnt mean your car likes it. your running around with less power because the computer is trying to save the engine. for what an extra 2 dollars a gas tank?

why is it so many people feel they know more then the people that built the ****** car.

follow the manual dip shit know it alls

[ryker]

Originally Posted by vtecmike1

why is it so many people feel they know more then the people that built the ****** car.

follow the manual dip shit know it alls

It is amazing that people will spend 20K on a car then cheap out on gas.


If you guys really want to be cheap and run cheap gas. Get a spark plug that is one heat range colder. This will decrease the pinging. But also might require spark plugs to be changed out in 20-40k miles instead of the factory 100k.


I own a highly moddified Harley sport bike (buell). So I am fully aware of the effect of octane and timing. I can run pump gas if I dial back the timing (get less power). Or I can run octane boost and/or mix in alchol race gas and set the timing correctly and bingo POWER!

Most people in a cage (car) will never hear the engine pinging. AC compressor noise and radio will mute it out. But trust me riding on top of the engine up a steep hill with lower octane fuels makes for terrible noise.

[dwm5f5]

Man...this thread went overboard... Obviously, higher compression + lower octane gas= detonation (that's fact, not an opinion). The car can only retard the timing so far, hence the need for aftermarket ignitions and the like...obviously there will be a power loss, and it also detracts from the cars ability to retard the timing due to other factors (because the car is already compensating for the lower octane).

All I wanted to know is if people were actually getting detonation from 88-89 octane under all conditions (idle through 8200rpm, different weather conditions, etc).

Our cars have a high enough compression ratio to require 91+ octane, why would Honda tell you, in addition to 21k for the car, you have to buy more expensive gas if you want to use their product, unless it was necessary.

My original question wasn't doubting whether I needed 91+...I f'ed up and put in 87.

[OhondaU]

Originally Posted by vtecmike1

just because our knock sensor will retard timing to prevent damage while you run 87 doesnt mean your car likes it. your running around with less power because the computer is trying to save the engine. for what an extra 2 dollars a gas tank?

why is it so many people feel they know more then the people that built the ****** car.

follow the manual dip shit know it alls

Your car can't like or dislike anything...its a machine. Sarcasm aside, the people who will be truly considering putting 87 in their car probably don't hit 100% throttle every day. And if you aren't using 100% throttle, you aren't using 100% of the available power. So will you miss it when its not there because you are now using 87 octane?

Oh, and the manual says the car will run on 87 without engine damage, which was the original topic of concern. I don't believe anyone argued with the fact that you will lose some performance.

If you do a lot of commuting that $2 a tank adds up, especially as gas prices increase and the gap between regular and premium will no doubt grow a little every time the price of oil takes a big spike. Sure, it may only add up to $100 dollars a year total savings by switching to 87, but at the national average you could buy one month's worth of gas with that savings.

And before someone with your obvious intelligence begins to prattle on about how "you shouldn't buy a $20K car if..." or "you should have bought the LX..." Not everyone bought the car solely for the engine performance. I know, this opens up an entire argument about how you could buy a LX or something and put the Si or HFP suspension on it...but you still don't get the 6sp transmission or the revvy engine. And I doubt that going from 91 to 87 will drop power output a full 30% on a stock engine. And even if it did, the revvy nature of the engine, plus having six speeds and decent handling give the Si a fun sporting character that the LX doesn't have, even if the engine were reduced to making only 150HP.

[ryker]

Originally Posted by OhondaU

Your car can't like or dislike anything...its a machine.

High compression engine creates heat. That heats up the cylinders, combustion chamber and sparkplugs. That exessive heat will cause the fuel to igntite aka detonation or pinging. Which the car doesn't like.

Sarcasm aside, the people who will be truly considering putting 87 in their car probably don't hit 100% throttle every day. And if you aren't using 100% throttle, you aren't using 100% of the available power. So will you miss it when its not there because you are now using 87 octane?

Pinging and detonation doesn't require 100% thottle load. Often it happens just on a moderate take off from a red light or up a hill.

[Firestrife]

This is what piston heads look like when too low octane is used.

[jameslewis178]

Originally Posted by Firestrife

This is what piston heads look like when too low octane is used.

is that a 2stroke dirtbike piston?

[OhondaU]

Ryker, if you want to delve into the specifics of detonation and octane ratings on high compression high rpm engines I can dig up the equations.

But before that nitty gritty embarassment ensues where the numbers prove you wrong, I will direct your attention back to the original question of this thread: will running 87 octane in the engine cause damage to the engine? The short answer from the manual: NO.

Now, can the combination of "low" octane (needs to be quantified) and "high" comression (needs to be quantified) cause detonation under the right conditions? Yes, no one argued that. HOWEVER, in this application the engine will be just fine on 87 octane instead of 91, or are you arguing with the vehicle's owner's manual?

Edit: As a case in point that the scenario of knock is not as straight-forward as you suggest: I have one motorcycle in my garage that has 12.4:1 compression ratio and runs on the manufaturer suggested 87 octane. Never a single knock....