vibrantvivid

im going to run a couple of tanks of 87 octane in my car and then see if it changes anything. i will let everyone know how the outcome turs out.

zeriak

ZoomZoomH,
Let's stop beating a dead horse.

Fact: Stock P5 and Protege Sedans ECUs are tuned to use 87 octane fuel.

Fact: MP3's have an ECU that is tuned to take advantage of the 91 Octane fuel with advanced timing.

You have proof from the carbonized plugs from above, that 92 octane is bad for your engine. If it's on the plugs, it's on everything else inside the combustion chamber. Don't believe me? Pull your plugs and see if they have carbon buildup. And for God's sake don't waste your money on Irridium plugs. Properly gapped NGK's will do the same thing for $5 that you would've spent $60 on.

ZoomZoomH

the horse is dead???? OK

THE END

Kranberry

Ok the horse may be dead, but I don't consider 1 case of dirty plugs to be proof. I've worked in research before and 1 case is not significant, there are many other factors that could contribute to carbon buildup besides 92 octane. It could be that Texaco has dirty gas, it could be any number of reasons. To be significant you have to have way more than 1 set of dirty plugs, and you'd have to have people who run higher than 87 octane on a regular basis, and check all their plugs. And then you have to have a set running only 87 octane and check their plugs.

1 is not proof...

Sorry to beat a dead horse, but I just had to add my 2 cents to some guy who thinks 1 set of dirty plugs is proof.

njaremka

i would attribute carbon buildup to the new engine breaking in syndrome. 3700 miles is not long enough for a newer engine to have broken in completely, and he could be getting a little blow-by or something that would cause his car to brun a little oil or so.

AND, higher octane will not result in an incomplete burn. octane is actually highly flamable. what octane does not do is ignite prematurely from being compressed. that is why it is reccomended for higher compression engines. lower grade gas will leave more carbon deposits, which retain heat after the combustion process. this heat, cobined with the heat introduced from compressing the air/fuel mixture, will cause lower grade gas to ignite prematurely causing 'pinging'.

becuase of these above reasons, i run premium in all my cars. and i have experienced improved gas milage from running premium in my cars. (i had a 94 grand am as a hand-me-down from my father. he only ran regular and got consistent 29-32 mpgs. i ran premium in it when i took over and got consistent 33-36 mpgs. oh, and my father drove more highway miles than city when it was his, and i ran more city than highway when it was mine.)

ZoomZoomH

holy Lazarus, the horse is alive again!!!!!!

njaremka

what horse?!? i agree MOSTLY with what you have posted, but not the bit where you say octane causes incomplete burns. show me where you get this from (outside of this forum) and i might belive you. i agree that you will not see performance GAINS from using gas with a higher octane rating than what the car was designed for. that's not what i posted above. what i am saying is that from MY experience, i have seen improved milage when using higher octane gas.

i know this isn't the only resource on the internet to explain it, but i really think you need to read this artical and the related links:
http://www.howstuffworks.com/question90.htm

Traveler

Octane rating is not going to contribute to complete or incomplete burn unless your engine was designed for high octane and you use lower. Then you'll have colliding flame fronts (pinging) which will bump your emissions up due to incomplete burn and will eventually kill your engine. I've seen some pretty severe cases of pinging that still haven't killed the engine yet so the idea that once your engine pings it's dead is a fallacy. BUT, it does damage things and will eventually result in a dead engine at an earlier mileage than normal. It is death on a boosted engine simply because the cylinder pressures are so much higher than stock. If you are using stock pistons and boosting, the tolerance for pinging is significantly lower than if you were using upgraded bottom end parts, headgaskets more suited to high pressure, etc. At really high boost levels, the cylinder pressures are so high that the oil barrier between the rod bearings and the crank will collapse if the pressure spikes at all due to pinging. Also, ring lands on pistons will burn through if the heat on them is uneven especially if there is a 'hot spot' where the pinging is localized. NOS aggravates the damage because you are adding oxygen to a hot area and that acts like a cutting torch in that area. It doesn't take long in that kind of situation to burn through a piston.

The big gain in fuel mileage isn't a result of the octane rating as much as the result of it being a better fuel formulation. The higher octane fuel is better refined and gets a better additive package than the lower octane fuel. Higher octane fuel burns slower, but it's not HUGELY slower. Since the fuel is more refined it usually has fewer additives added to it that make it meet minimum requirements than many 'regular' grade fuels have. I also have seen improved mileage with just about every car I've owned if I use premium fuel. I've spoken with people that work for refineries (I grew up and lived near several of them for a long time) and they assure me that the reason for that is better fuel formulation.

92 octane fuel doesn't have many octane boosting additives added to it while 85.5 (mountain areas) or 87 do. The base fuel that becomes 87 octane is actually barely 80 in most cases. The rest is obtained with additives. 92 octane usually (depends on the company refining) starts with a much better base fuel (87 or better) therefore needing less added to it to meet the 'premium' requirements. Since additives add mass and aren't as combustible as the fuel they are substituting for, most times you will see an increase in fuel mileage since the BTU content will in fact be higher for a gallon of gas.

It works the same with diesel engines. A higher cetane rated fuel will usually increase your fuel mileage not because it has more resistance to knock (that's what makes a diesel run anyway, controlled knock) but because it is a higher base number fuel which means more good fuel and less additives. There's more energy in it to start with. We used to try running 'premium' diesel and regular diesel back to back in our last big rig and the results were usually .4-.5 MPG better with the premium fuel. That may not sound like much, but it's a huge difference when you have a truck getting 6.75 MPG average and you bump it to 7.2 MPG average. It ends up saving a LOT of fuel over the course of the year and it more than makes up for the increased cost of the fuel by reducing engine deposits and increasing injector life. It also ends up saving over $1000/year on the fuel bill.

Sorry for the long post guys, but I couldn't think of a shorter way of completely explaining this!

njaremka

traveler, you rock! good stuff...

distance

You can't just use 87 octane when your manual reads 87 or higher. Case in point is the contour SVT. It says that you can use 87 octane but recommends higher octane for better performance. Personnally I use 87 octane. I have not noticed a diff. in mileage or power in my 01 protege. My 98 plymouth voyager gets better fuel economy and runs better on 89 octane. "Manual also says 87 or higher ocatne" Where as other manuals say 87 octane!!!!