Different parts of the world measure octanes differently, so it's all relative. But with a hotter and drier climate, a slightly higher octane fuel might serve you better. Running (US) 91 in a US Fit is pointless and even counterproductive.

 

not true. UNLESS you had your ecu retuned to USE that extra octane. otherwise it is just going out your tailpipe

 

Can you point us to the testing that someone has done in hot temps with a scan tool showing that timing isn't being retarded due to the detection of knock?

 

my fuel economy is awesome in hot weather.

if your ecu isnt tuned to run on 91, it doesnt know its there. you are throwing that extra 20 cents per gallon away

 

Jesus christ, read my postings earlier in the thread. That being said, if you are in a HOT and ARID climate like some parts of SOUTH AFRICA and PUTTING LOAD ON THE ENGINE, running the equivalent of US spec 89 octane fuel might be smarter than running just US spec 87 octane fuel.

 

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.


What Octane Rating of Gasoline Should I Use?

 

no need to use god's name in vain

 

That's only if that is his God. Who gives a **** anyways, either refute it or stfu.

 

Holy crap, with gasoline you get a violent explosion.

In africa or wherever you may need to bump octane because of heat or because the gas is sh!t.

Anybody is free to run dyno's with different grades of fuel to see if the ecu learns up and advances timing for more power.

However if it is/was true the clever guys here would already be on top of it.
But I suspect the only benefits of higher octane have been realized with the forced induction guys.

Chill out already

 

This might help...

https://www.fitfreak.net/forums/fit-...tml#post481366

A GD3, at 58 degrees F allowed more timing advance (or less retard) with 93 as compared to 87 octane. Double that ambient air temp (not uncommon for air temps in South to be 110+ on the roadway) and the difference would theoretically be bigger. I don't see how anyone can say increased octane offers NO benefit. Whether it's noticeable, worth the $, etc is debatable.

 

This thread is going nowhere fast.

 

txmatt,

cool, you got a link to that??

 

Thought it was in my last post. I'll try again...

https://www.fitfreak.net/forums/fit-...tml#post481366

 

doh! tx txmatt yeah your links was there, 3 deg advance is not bad

I'll have to search resetting the PCM

 

the only time i will be increasing the octane i run to higher than 87 is when i have over 100k miles and that is only if it is necessary. as engines age the deposits in the combustion chamber increase effectively increasing the compression ratio.

with how precise the air/fuel metering is on modern vehicles, however, i may be looking at more like 200k+ miles? either way, "if it ain't broke don't fix it." if it runs fine on 87, as mine has thusfar through 90+ degree temps all the way down to temps in the teens, then i'm sticking with it.

 

87 fellas. Go for quality of fuel, not quantity of octane. Higher octane in an unboosted, stock compression fit is stupid. Unless you think those poor oil companies deserve your charity. Check out Top Tier Gasoline

 

In my monster 99 Civic, I have to run 91 Octane, or else it'll ping and run poorly. I know this because I tuned it to run on 91. It's got a compression of approximately 9.9:1, and I run a lot of advance.

If I put lower than 91 into it, it'll ping and it loses power in the upper end.

If I put higher than 91 into it, it'll hesitate, and I lose power across the whole band, but with most of the power loss in the low-end.

When I put 91 into it, it runs perfectly.

^^ I hope this helps people understand.


On my fit, I've noticed a little hesitation, and some lope when at idle, but I assume this is due to the lean-burn design of the engine. Maybe someone can correct me on this. The fit does not have a knock sensor, so one can assume that when the manual says to use 87, the engine is only tuned to use 87.