http://theserviceadvisor.com/octane.htm

The type of gasoline to use is one of the most misunderstood areas of vehicle ownership. I am going to offer some ideas that I hope will save you a few bucks on gasoline.

The first rule of thumb is that higher octane gasoline is not necessarily better for your vehicle.

WHAT IS OCTANE RATING?

Octane, by definition, is the resistance to burn or detonation. The higher the rating, the slower the burn when ignited during the compression burn cycle of the piston. The higher octane allows for better control of burning for high compression engines. So we want to match the correct octane rating of the gasoline to the engine design to ensure complete burning of the gasoline by the engine for maximum fuel economy and clean emissions.

I THOUGHT GASOLINE WITH HIGHER OCTANE REDUCED ENGINE KNOCK?

It did in older engines using carburetors to regulate air/gas mix They cannot as accurately regulate the air/fuel mix going into the engine as a computerized fuel injector. Carburetors need adjustment, as a part of regular maintenance, to keep the air/fuel mix as accurate as possible. So many times, these adjustments were not made regularly causing too much fuel to be mixed with the air. When this happened the gasoline would not burn completely soaking into carbon deposits. This would cause a premature ignition of the gasoline due to the intense heat in the engine cylinder creating "engine knock." When this happened, people would change to the higher octane/slower burning gasoline to resist the premature burn, thus minimizing the knocking problem. And it worked. Good solution.

However, since the middle to late 80’s, engines are designed to use fuel injectors with computers to accurately control the air/fuel mix under all types of temperature and environment concerns. However the accuracy of the fuel injectors and computers is based on using the recommended gasoline for that engine.

Most cars are designed to burn regular unleaded fuels with an octane rating of 87. If the vehicle needs a higher octane rating of 89-93, there is documentation in the owner’s manual, as well as possibly under the fuel gauge and by the fuel fill hole. Usually you will see this rating for high performance engines only.

WHAT IF I PREFER TO USE GASOLINE WITH HIGHER OCTANE RATINGS?

You can, but there are no real benefits, other than the gasoline manufacturers making more money off of you. When you use a fuel with a higher octane rating than your vehicle requires, you can send this unburned fuel into the emissions system. It can also collect in the catalytic converter. When you over stress any system, it can malfunction or not do what it was designed to do properly. In the early 90's, an early warning symptom was a rotten egg smell from the tailpipe. Easy fix, go back to using regular 87 octane gasoline. The rude odor usually disappears after several tanks of gasoline.

DOESN'T HIGHER OCTANE GASOLINE HAVE MORE CLEANING ADDITIVES THAT ARE GOOD FOR MY ENGINE?

No. Government regulations require that all gasoline contain basically the same amount of additives to clean the injectors and valves. The only differences are the type to help create the different octane ratings. All gasoline burns at the same rate, it is the additives that create the different octane ratings for the different types of engines.

REFORMULATED GASOLINE

In some major cities with air pollution problems, reformulated gasoline is required. It is an oxygenated fuel, that burns really clean but can slightly lower fuel economy and engine performance. If your engine is really dirty with carbon deposits, it will also cause pinging or premature burn. In these types of situations, you may want to consider stepping up to the next grade of gasoline.

The bottom line is to use the type of gasoline recommended for your engine. In some cases, like towing, or other stresses on the engine, you may find a higher octane fuel helpful.

NOTE: I do not proclaim to be an expert in these matters, but am only presenting an overview of what I have discovered in my work in this industry with the different auto manufacturers.

 

your saturn was detonating (very bad for your motor), thats what the knocking sound is. 93 octane takes longer to ignite and burns more slowly than 87, that's how your knocking sound went away. use 87 because that is what's recommended by honda, if you use 93 octane on the fit it might make it run even worse because it may not burn the fuel completely then it will advance your timing to compesate. if it doesnt detonate then you dont need high octane, if you go with forced induction or nitrous then you moght want to use high octane.

 

http://en.wikipedia.org/wiki/Octane_rating

 

This is very true.


The ONLY way you'd gain ANYTHING by running higher octane would be if your engine is already compensating for detonation by retarding the ignition timing with 87 octane. Moving to a higher octane gasoline would remove that compensation, and could give a little more power and efficiency.

Maybe the Fit does adjust the timing for use with 87 octane, and might benefit from a little higher.

 

I would think more. higher octane ratings means it needs higher pressure to ignite. If a car is designed to burn 87, it wont' have a compression ratio high enough to burn up all the 93.

 

Use the 87 recommended by Honda.

 

Kinda sorta. 'Octane' ratings are basically a comparison ratio of heptane to octane.

Heptane is very unstable and tends to detonate (spontaneously ignite) when compressed. Octane is very stable and resists detonation when compressed. The 'octane rating' of a gasoline is a rating of it's resistance to detonation as if it were a mixture of only heptane and octane.

'Needing' higher pressure to ignite is not true, after all, gasoline engines have spark plugs to ignite the fuel/air mix. What you want to AVOID is ENOUGH compression to cause your fuel/air mixture to ignite BEFORE your spark plug fires.

 

Yes.

87 is the correct octane unless you note knocking under the conditions you drive or with time as your engine gets worn out.

Hopefully your area gets decent 87 octane fuel (search for top tier gasoline).

 

I just checked and in the break in and fuel recommendation section the manual says '87 or higher'.

I had been buying mid octane, 89, mistakenly thinking i had read 88 or higher earlier. I'll drop back to the low around here which is usually 87 i think.

It also talks about using quality gasoline with cleaning additives... I don't pay a lot of attention to which brand gas i buy... the 'system 3' advertising has penetrated my brain though.

 

All you are doing by buying the higher octane gasoline is throwing your money out the tailpipe of the car.

 

interestingly enough, some high octane fuels(93) are actually worse than low octane(87) and these are ones everyone should stay away from. if you ever see a store selling "oxygenated" fuel, steer clear. this fuel has had oxygen impregnated into the mix which helps prevent detonation much like adding "octane" in higher percentages to the fuel......but what it also does is remove energy producing mass out ovf the same volume as regular fuel. the oxygen in this fuel does not burn, it only helps the fuel burn cleaner. the best ****ogy would be, take a 16 oz glass and fill it up with your favorite beverage and next to it fill the same size glass with ice and then fill it with the same beverage. sure the ice is nice, but if you're paying for what's in the glass, you're wasting your money on the ice. it's too bad oxygenated gas is both more expensive and packs fewer useable BTUs screwing you twice. so compare those two fuels and 87 octane is the better fuel when you engine doesn't require anything more.

as stated above, stick with the 87 until there's a problem.

 

i think the octane will only matter on what car you use. the car is tuned from the factory to use a certain octane and i believe the fit will not require anything greater than 87. c'mon, it's not a built 1200whp LS1 camaro that needs alcohol or something. it's a fit for crying out loud!

 

We also have a 01 Odyssey, and the specs say:

Horsepower @ rpm(SAE net): 210 @ 5200*
Torque (lb.-ft.@rpm): 229 @ 4300*

* With premium unleaded fuel (205 hp/217 lb.-ft. with regular unleaded fuel).

It looks like with that engine, 93 brings in a few extra ponies. How come this is not the case for Fit?

Thanks

 

wow, this is very interesting... i'm gonna do more research.

 

Its true that it needs higher pressure to ignite but you also get unburnt fuel existing on the engine parts which keeps temperatures down and resists a lot of carbon deposits.

 

so is 87 or 91 octane better for my engine? (I like to drive at high REV's most of the time)
The highest octane rating that I can get at a gas station around here is 91, unless I buy 100 Octane race gas that's about $5 a gallon.

 

I know Honda recommends 87, but I just moved to New Mexico and they offer 86 octane instead of 87. Anyone think it'd be a problem to use 86?

 

isn't the odyssey also a 3.0 v6? i believe they tuned that particular engine for 91 octane, to use anything "less" is what will hurt the car's performance.

it's not the case for the fit because that 1.5 litre engine doesn't need a lot of octane because it's not tuned agressively.

however you cant compare the fit to the odyssey because look at it this way. if the odyssey is tuned for 91 octane, then using anything less could be bad.

so if the fit is tuned for 87 octane, using anything less than that could be bad. so the only way for a fit to "lose" power or hurt the engine is to use 85 octane. pretty much anything less than honda tuned it for.

 

yes 86 will hurt it just a tiny bit. if i were you, i would go to whatever the medium grade is. i assume it's 88 octane? and 90 octane for premium?

 

No. I had an '01 Odyssey V6. It only required regular unleaded. No problems. You just had to use higher octane if you wanted that certain tested horsepower. I drove it 5 years/87000 miles on regular unleaded.