And yes Wikipedia is the end all be all. I'm living here and I guess you don't realize what the > means? GREATER THAN!!! The stations all around me use 94 and 99 RON for regular and premium.

 

So Arco isn't a top tier brand with less additives and uses higher levels of Ethenol. Even Arco admits a 2-4% decrease in MPG because of the ethenol. Like 15% instead of 10%?

The internet told me.

I guess even Honda doesn't want me to use Arco. Wonder if Valero is the same......

 

I guess you don't realize what "standard" means? I'm sure Honda Japan issues unique specifications for "around you."

And for the wiki doubters, I also cited a Japanese oil industry presentation showing the same thing...

 

And yes I know what a standard is. In that last source you posted, it doesn't list the Octane way of rating, just lists a number, so how do you know what method was used to come to that number? You don't, you can assume that it is just RON as that is normally how Japan measures, but no definitive there. Interesting that 94RON when converted to the R+M/2 method used in the US comes to right around 89. The Wiki article lists 1986 or was it 96 for Japan, yet this Japan thing came about in 2006. So again, is Wiki right and did the "author" of the Wiki just go ahead and assume as well that the number was RON?

Around me goes as far as 600km radius (North and West, can't go that far East or South or I would be in the water) I'm in the Tokyo Metropolis area, the most dense area in Japan where more than likely the most fuel is consumed in Japan. Even when I lived down in Okinawa, left there in Jan 2008, after that Oil standard was created, the RON was 94 and 99.

I'm sure you will try to find more to back up your profound love for regular gas and dismiss those that use premium as just wasting money or whatever you may deem us, but some of us are not just A-B types with their vehicles and use them for recreational purposes and have altered them from stock beyond visual modifications.

 

I'm curious...

Assuming no modifications are done to the car (or in my case, minor via drop-in k&n filter)... what conditions can cause knocking in an otherwise healthy engine?

Now, that being said, the Fit engine, as CasualFitOwner noted, has a 10.4:1 compression ratio (which is generally viewed in the past as used with higher octane gas, correct?)... and as most everyone knows, the Fit can adjust the timing to limit knocking with regular gas.

If the engine is running such, that the timing is retarded due to knocking with regular gas (retarded enough that you don't notice any knocking), how is the performance compared to advanced timing with premium gas?

 

I don't think anyone here (myself included) is saying it isn't possible to mod a car designed to run on regular gas to need/benefit from higher octane. Short of an aftermarket tune, forced induction, or aftermarket cam, I don't know what it would be.

What we are saying, is the Fit was designed for regular gas, and without modifying it, won't benefit significantly from higher octane.

You are equivocating over the definition of regular gas, which by Japanese standards (89RON) is probably lower AKI, using the (R+M)/2 method, than 87octane regular gas sold in the US. Exact comparisons aren't possible as fuels in Japan are not tested using MON. If you really think Japan publishes their standards using (R+M)/2 instead of RON, I welcome you to find something showing this. JIS K 2202 seems to be the pertinent standard.

Profound love for regular gas? mmmmm no, maybe profound love for common sense...

 

In an unmodified Fit? No one has completed dynamometer runs on the same car with 87 and compared this with higher octane that I'm aware of. For other makes of cars, I'm unable to find any that show an improvement. There's the Car and Driver article from 11 years back that shows the opposite. I offered to pay costs in another thread for anyone interested in testing this, but didn't get any takers.

I think it's significant that oil companies do not advertise increased power from higher octane in cars where it is not recommended or required by the manufacturer. They certainly have the resources and incentives to do so if it weren't for a little thing called truth in advertising. If anyone can find a US ad stating this I'd like to know.

 

Oil companies CAN'T advertise it, because cars have been specifically designed for "lower" or "higher" octane. Hence the "recommendation." But I have seen a mention, I think, even from oil companies about "restoring" life to an older car (where it knocks due to carbon build up).

I'm not talking about a simple dyno run either.

If I'm not mistaken, one of the causes of knock... the heat in the chamber causing the mixture to ignite prematurely. So a car that's been driven at high rpm for the last hour would more likely produce knock in regular gas compared to once that's just been low rpm crusing. No?

 

I think you're right, but the detection of knock and subsequent immediate timing retard must not affect power significantly. And by significant, I mean more than the standard deviation of controlled test runs on a dyno. I'm not sure what you mean by a simple dyno run, but it's a given the engine's hot running at WOT sitting on a test platform.

Again, this is on an engine designed for regular. One designed for premium, the average driver might be able to tell a difference when using regular gas, but he'd have to be odd to want to try it.

An older car that knocks audibly due to carbon build-up would benefit from higher octane. It might even keep worse damage from happening.

 

Exactly Goobers, just because a car was "designed" and advertised that using regular fuel works, the majority of people buying a Fit are not ones that are beating the crap out of it and would likely never push their engine into seeing the ignition being retarded way back from using regular fuel.

"Common sense" would dictate that the naysayers would take into account those that have actually hooked up a ScanGauge or similar device to their OBDII port and have seen the data first hand from the ECU what is happening to timing based on driving conditions and fuel used. Even those that use a higher grade of fuel have stated if you are putting around and not pushing your engine to extremes, you are not really going to see any real benefit to running more than regular, but the naysayers never look at that and just dismiss those using higher than regular as not having "common sense" I guess. Ignorance runs rampant and some of those few even will not test on their own accord and just believe everything published on the Internet, especially if it comes from QuikTrip. Though not believe first hand testing from individuals because well they are not corporations I guess. You would have to ask those types why they will not accept first-hand testing from individuals for their exact reasons.

 

Pretty much all the dyno runs I've ever seen have been the basic, go from idle to red line and then stop.

What I would like to see is an engine running at, say 2500 rpm for 30 minutes, then then some sort of sequence of WOT for varying amounts of time. The sequence is then repeated after the car has been "idling" at say 5000 rpm for last half hour. Then do that whole thing with regular gas and then premium gas.

And all of this has to track not only the "HP" measured on the dyno... but the timing in the engine itself. Did it advance, did it retard?

You say it shouldn't be significant... according to who? Engineers (and Honda decision makers) can say a set variation isn't significant... but what is their definition of significant?

And for who?

For the everyday person that doesn't do bupkist? For those that are more "spirited"?

 

That'd be some expensive testing: hours of dyno time. I don't think there would be a significant difference in power output. Significant in engineering terms (greater than the standard deviation of the set of test data for a given level of certainty).

I don't doubt timing retards more under spirited driving using 87 octane than 91, but there is no evidence this reduces power output significantly in our Fits (or any car whose manufacturer does not recommend higher octane). I'm sure it's fun to watch on a scangauge though.

 

First off you have to look at a engine as individual engines. At 2000 rpms each engine fires it plug 500 times per minute. Every burn cycle is different because of different fuel properties being burnt. Some lean and some rich. 1000 to 2500 the engine is knock limited at loads over 70 percent so it will add fuel and retard the timing and the EGR takes some of the pre burnt fuel and routes it back to the engine. If the EGR has alot of fuel it makes it hard for the spark plug to fire and causes misfires but not all cylinders need the EGR.

Honda says the engine is tuned to MBT with 91 R/M fuel which is in the middle of the street octane rating. There is a lot of other variables but the idea is to keep the intake cool and the pistons cool with higher octane.

Here is something I found a few days ago and if you think .57 of a second is not much its about 10 HP using less fuel. The Hindu : Metro Plus Delhi / Wheels : On a higher octane

 

how about this: Fuel saving - a professional engineer's view

And a few quotes from it...

 

Engine loads are also dependent on A/C and lights use. At idle with nothing on the engine load is around 35 percent. Taking off to get to speed the engine loads are 100 percent and at cruise around 50 to 65 percent or higher depending on speed and terrain. A/C the idle loads are 55 percent and Lights only at idle is 50.

Also the throttle is electric so even when pressing down very little the throttle could be wide open depending on load and fuel mapping that is dependent on the fuel used and corrections stored in Random Access Memory.

 

And I do a LOT of taking off... and not the slow kind either.

 

I accept that people with gauges say that the timing is changed with different octane fuels. How much it affects power or economy, though, is a different story, and that's the relevant debate.

And as far as the decade-old Car & Driver article, I don't think they tested any 10.5:1 compression engines running on 87 octane. I don't think anyone here is saying to put high octane fuel in a lower-compression engine.

 

I'm not sure if I remember correctly but I recollect that in the mid 60s through early 70s the octane rating for Texaco Fire Chief ( regular) was 94... I can't recall what the rating was for Sky Chief but I do remember some gas stations at the time advertised octane levels as high as 108... I was using 108 octane in a 4 stroke racing bike I had built the engine on with a Wiseco forged piston as late as the mid 1980s...93 isn't really what could be called high octane... People spend a lot of money to change the air to fuel ratios and ignition timing to gain more power on virtually stock engines as well as modified ones. They are looking to use as much ignition timing that is safe to use with a safe A/F ratio with out causing detonation... The cars today have ECUs that quickly respond to add fuel and pull back ignition timing when it is necessary to avoid ping and it is going to do that more often the lower the octane rating of the fuel being used is... Just like a firearms enthusiast will do or have things done to improve the accuracy of a rifle or pistol beyond what a less skilled shooter would notice including the use of more expensive ammunition. Automotive performance enthusiast are likely to appreciate what amounts to negligible changes in performance to a person that isn't as interested or lacks the ability to even notice an improvement... I'll admit that a person who is light on the throttle and doesn't tach over 4000 RPM or carries passengers on a regular basis is going to notice an improvement in power or fuel mileage because I never have to any noticeable extent when not doing these things..

 

Same here. The thing runs the same on anything with fumes.

 

The car has a paltry 117 hp. Changing gas, air filters or any other mundane alterations would provide un-noticable (imaginary, maybe) changes in power. Maybe some blip on a dyno, but that is about it.