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The manual calls for 87 octane and Top Tier. That's what I use and the car operates wonderfully.

 

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I run mid grade 89 , but I run that on all my vehicles. Noticed it prevents knocking compared to 87. Some fuels I can hear the engine knocking and pinging at times. 89 Never did it. It is not as noticeable with the GK being a DI engine. I could run 87 likely and it would be just fine.

 

I'm waiting for all the non-American/Canadians to come in and say 87 is too low

 

It's designed to get a complete burn with 87 octane. VVT (vtec) will slow down timing if it detects knocks, but I don't know of a system that can detect higher octane fuel and advance timing to get better performance. Cars that can use higher octane will "recommend" or "require" it.

If someone can show more power with higher octane, great, but I'm skeptical. Small improvements in fuel economy are within the margin of error, so that's a harder case to make.

 

I'm using 87 pump octane (91 RON) from my local Arco AM/PM Mini Market station with no issues so far.

 

All Honda auto motors are set for MBT timing with 91 r/m octane. The difference is between the two 87 or 93 octane is about 10 degrees of retard. Air fuel ratios of 14.7 on premium at MBT or fuel as rich 11 to 1 or 30 percent more fuel depending on timing retard. I averaged 38 lifetime mpg with my GD3 manual with 3 winters and 2 summer on premium in Chicago. My new car is averaging 41 mpg for the last 3 years with the best of 50 mpg twice but usually around 47 mpg in the summer.

 

I was thinking about what i post here a couple weeks ago about the octane required for the motor. So I was just reading several articles and I got into a simple conclusion.

High octane for high compression radio
Low octane for low compression radio.

Based than the new honda fit(3gen) has a high compression radio of 11.5 to 1 is is recommended to use high octane as my maintain book recommends 91 octane.

If we based on the theory that the compression is even higher than honda civic SI (11.0 to 1) or even the accord accord coupe and even the bmw 3 series e90 and all those cars are 91 octane.

But after reading more I goy into an article of the new mazda 3 with the sky active technology.

::
Premium, 91-octane fuel is required for the Sky’s not-so-staggering 163 hp at 6000 rpm and 155 lb-ft at 4000, but Mazda is proud of its exceptionally wide torque band for enhanced real-world drivability. To enable running on regular gas, the U.S. version will have a compression ratio of 13:1, which means fuel economy and torque will diminish by about 3 to 5 percent, according to Mazda. The premium-fueled Sky we drove was perfectly adequate in the Mazda 6 prototypes, although acceleration was rather leisurely—far slower than the current Mazda 6 with its 168-hp, 2.5-liter—giving us plenty of time to wish for a bit more smoothness during the extended time in each gear. But being in the lighter Mazda 3 would help, and the tradeoff for near-diesel levels of fuel economy is probably worth it.::
:::



I would love to see your thoughts and based on facts and research and not old myths. Any insights?

 

Compression RATIO is a theoretical difference between the cylinder volume at bottom dead center divided by volume at top dead center. Actual cylinder pressure also has to take into account valve timing and overlap. Combustion chamber shape has to be considered as well, when determining how much octane rating is necessary for a given engine design.

In short, compression ratio is only part of the story.

 

The American manual says 87 octane, our lowest. That's what I use and it's fine.

 

Correct theory when comparing apples to apples. You have to remember that the GK has a direct injection engine. Directly injecting the fuel into the combustion chamber cools the charge better which prevents pre-combustion, aka knock. Typically you can run 1.5-2.0 points higher compression on a DI motor when compared to a similar port injected motor.

 

Just filled up with premium and noticeable difference in smoothness of engine and slight power boost. Engine just runs better! I am at 19500 miles and have had nothing but regular lower octane fuel so far. Engine is snappier and more responsive, even sounds slightly different at 3-4 k. I noticed this in my old ford ranger as well, better mileage and slightly more power. I know people might get offended by this, but I swear I can tell a difference.

 

And you probably do feel a difference. It's higher octane and you have 19500 miles so you probably have deposits in the fuel system and valves, which raises your engines need for more octane. But. The higher octane is completely unnecessary in an economy car. Don't want to offend anyone but this thread is dumb. It's an economy car, not a 5.0 Mustang. Honda calls for 87 octane. Why would you ever spend more on gas you don't need? At the most I will add Amsoil P.I. gasoline additive every oil change or every 4000 miles like Amsoil recommends. This stuff does work (I have used it before) and with direct injection it's needed more than with a standard injection.

 

87 octane top tier. Higher octane is a waste of money unless the manufacture recommends it.

 

I have no intention of trying to get extra hp out of the small engine, I realize it's a tiny car. As far as additives and premium cleaning the valves, well that's not gonna happen with direct injection from what I understand.

 

87 octane from reputable gasoline company. I also give a thought toward minimal debris in the underground storage tank (quality gas station, volume turnover, don't buy during/just after fuel truck stirs things up). I prefer not to fill up at "Mr. Happy Gas" no-name station but maybe I'm a victim of perception vs reality.

 

My bad, didn't mean to say valves in my post. The valves don't get touched. Here is more info on Amsoil pi and direct injection. I am not affiliated with Amsoil in any way. But I have used this product and it works well.

Gasoline direct injection (Gdi)
Gasoline direct injection (GDI) differs from port fuel injection in where the gasoline is introduced prior to com- bustion. In conventional port-injected fuel systems, the fuel/air mixture occurs in the intake manifold. In GDI engines, gasoline is injected directly into the combustion chamber under very high pressures, similar to how diesel engines operate. This results in better control of the air-fuel mixture, allowing greater power, torque and operating efficiency.
Most vehicle manufacturers are now producing vehicles incorporating GDI technology, with several reasons for their increased production. First, today’s injector systems are computer-controlled and capable of deliver- ing extremely accurate and rapid distribution of atomized gasoline. The fuel can be sprayed directly at the hottest part of the combustion chamber, which is near the spark, improving efficiency. Second, because the fuel supply is more precisely controlled, combustion can occur at leaner air-to-fuel ratios. GDI engines use a very lean mixture of 40:1 or greater during light loading conditions. The lean ratio means less fuel is burned dur- ing combustion, increasing fuel economy. Finally, when atomized fuel is injected into cylinders at high pressure, the combustion chamber temperature decreases slightly, helping further increase efficiency.
The fuel injectors in GDI engines, located directly in the combustion chamber, are exposed to elevated tempera- tures and pressures. This severe environment makes them more susceptible to deposits that impede the spray
Test Method: Motored Dyno D5500 Type Road Simulation Cycle

AMSOIL P.i. provided an average fuel efficiency increase of 2.3%, with one car showing improved fuel efficiency of 5.7%.
AMSOIL P.i. contains powerful detergents that clean deposits that form in combustion chambers and on fuel injectors, improving fuel economy and reducing emissions.
Gdi Clean-up test
To determine its cleaning power, AMSOIL P.i. Perform- ance Improver was tested in a Volkswagen Jetta with GDI fuel injection. Upon accumulating 3,000 miles, all four fuel injectors were tested to determine baseline fuel flow. Clean-up using P.i. increased fuel flow from 95.5% to 97.7% on the most severely-affected injector, and an average flow improvement of 2.3% (from 96.8% to 99.1%) across all four injectors was observed following use of P.i.

 

And more....

Pros and Cons of Direct Injection Engines - Consumer Reports

 

So you can use a cleaner like amsoil pi for the fuel injectors, but not carbon buildup? Is it safe to use in our d.i. engines? Anything else I can do to take care of my engine? Thank you