As many others here have indicated, anything higher than 87 octain (unleaded regular) is a waste to money. Even if higher octane got slightly better mileage, would it justify the higher price? Even with what looks like a high compression ratio, I'm believe that a lower rating would work for a short time.

 

I don't know if the US octane rating is different to the UK but 95 is 'normal unleaded' here

 

it is different, europe uses RON and US uses an equation of (RON + MON)/2 which is the anti knock index (AKI)

 

OK, just did a wander round t'interweb and found this

So our regular 95 is equivalent(ish) to your mid-grade 90(ish)

... and your gallons are smaller than ours too. Highly confusing.

 

At 11.5 to 1 compression the FIT is right on the edge of being able to exploit higher than 87 octane, ON a very damp high density air day at the drag strip hitting the limiter on shifts you'd see a benefit (VERY VERY small) If you had a Exhaust gas temp gage. It would cool down a bit. Same with say a 100 degree day in the desert, the 92 will reduce ping with the low density air and high inlet air temps, the ECU can compensate but it does so based other sensor input.

The normal rule of thumb is 12.5 to 1 and higher benefits from premium fuel but the variables in the OEM ECU tuning make it unlikely that you getting much power..

Computers rule.. For instance my KTM 950 motorcycle has a carb, no computer fuel control, and 11.5 to 1 compression just like the fit, 92 is mandatory.. Barely starts on 87... It has a special jumper you can remove to limp on lower octane, retards the timing but its drives like crap..

 

I'm not sure, but you appear to be implying that humid air is denser than dry air. The opposite is true, although it's a small difference when compared to how density varies with temperature.

 

I'd love to see a definitive answer - California Regular 87 or Premium 91. Just to be hopeful I'm going to fill with 91 for my next weekend tearing through our San Diego East County winding and hilly two lane roads.
Vive Fit!

 

I buy 87 octane at Costco and Quick Trip & once in a great while at Chevron. These 3 brands on the "best gas" list and no problems using this gas, even in our infamous 115 degree summer using the A/C.

 

Been using Shell 93-Octane since new.

 

wow wow...
never expect fit should be fed with something higher than 87.
It's a budget car, not a luxury car. And U.S's fuel quality should be better than most other countries.
but it's only my opinion. 13k, 87 only, no problem at all.
Winder is always lower with heat on-temp. I have ~29 MPG city only. Summer this number will be higher.

 

Not just your opinion. It's in the manual to use 87.

 

I have been using 87 with no issues in my 2009 Fit. I have NEVER heard spark knock even under WOT in the heat of Summer. I stick with top tiers only. However, I'm curious to try a local supplier's ethanol-free fuel (Wawa). Currently that sells for $2.69/gal, although 87 regular is at $1.69, so a bit of a price hit there. No, there's no way any mileage added will offset the cost difference, but it would be an interesting trial experiment.

 

Most of the Fit owners in this forum are from United States, I have read a couple of post stating that manual says regular 87, but my Fit's manual says "Unleaded petrol, research octane number of 91 or higher".

My country's regulation mandates that regular fuel should be minimum of 89 and premium 95 (octane).

I've been using regular since the last two full tanks, no knocking sounds so far, should I switch?

 

Go by what your manual says. Octane ratings between in the US and some other countries are calculated differently, so your 91 could be equivalent to our 87.

 

I tried an enthanol free pump at a station near me and it ran terribly. Probably because they sell so little of that gas that it stagnated.

 

Octane is measured in 2 different ways and expressed in 3 different ways.

One is Motor octane. The second is Research octane. Research is always higher by around 7 to 9 points for the same fuel.

So we have a research number, a motor number and in the US and Canada we have an average of the two expressed as R+M/2. So your octane number of 91 is approximately equal to our 87.

 

I use strictly 87oct from either BP, Circle K, or Sheetz. Never had any issues and BP tends the get me the most gas mileage per tank. I have tried ethanol free fuels but didn't see any benefit from it.

 

Interesting,, my Jeep gains about 5 MPG on Ethanol free vs E-10. Gets me almost up to 20 MPG..

 

That is my experience too. Where I can get pure gasoline (I can't in SoCal) I usually get a couple of MPG better. I also like the fact that I'm not forced to subsidize ADM. Gasohol is a scam writ large.

I've not had any problems with my older vehicles concerning ethanol, but I have replaced all the fuel lines with modern ethanol-resistant materials. Luckily, my carburators and fuel pumps seem to be compatible with it.

 

Agree that Gasohol is a scam. I wish I could find cheap ethanol-free gas here but I go for the cheapest stuff at the local Grocery Gas Station. It's Top Tier so I don't worry about how it might affect the car or mileage but it does bum me out that I'm paying for someone to use petroleum to produce corn to produce...petroleum.