I know that I've asked this question before but what Fuel Octane Rating do HCH II drivers in the U.S. use?

Thanks.

I use 87 in my HCH I.

-Charlie...

87 Octane.

I am in the mile high city. I use 85 Octane in both of my vehicles. The Honda service guys said the 85 works great at this altitude.

In Dallas the choices are:

• 87 for regular unleaded
• 89 for mid-range
• 92 for premium unleaded

Like Mr Kite said, regular unleaded is 85 in Denver (think it's minus 2 for all gas in the mountains...). I'd love to hear the explaination for the octane range.

61.5mpg lifetime - 82mpg in recent months

Best Run >
www.cleanmpg.com

"fanatic" is what the lazy call the dedicated

Keep in mind, the US may use a different rating system then found elsewhere. There is RON, MON, and PON.

The U.S uses PON which is an average of both RON and MON. So 87 PON is not the same as 87 RON or 87 MON.

87 octane works fine. Here in the Midwest, we can buy 10% ethanol with an 89 octane rating at 3 cents less per gallon. Higher octane doesn't mean better mileage. I get about 3-4 mpg less with the ethanol blend.

Ethanol contains less energy than gasoline so that makes sense. The advantage of ethanol is that it's renewable.

The explanation is simple... at higher altitudes gas is harder to detonate because of the lack of oxygen... it acts as a octane boost if you will. So you can go for lower octane gas because it will not pre-detonate.

I'm currently using 91RON, which as I understand it is about 87-88PON (which as I also understand is a combination of RON and MON).

The next option we have here is 95RON then 98RON and now 99RON.

Once again, as I understand it, the RON / MON rating has little to do with extra power (as we are all being told it does in Aus) but more to do on how much compresson the fuel can take before it pre-ignites. ie. 98RON can run in higher compresson engines without "knocking".

Has anyone tried a higher RON / MON / PON fuel, and was there any noticable difference in FE?

On another point. I have noticed my FE improve markedly since -

1/ I hit 14,000 KLM's

2/ I increased tyre pressure to 44psi


But I still can't crack 60mpg....what the hell are you guys doing to get that high?

The combined FE rating in Aus is 4.6L per 100klm.

Which equals 50mpg using the US gallon = 3.785 litres?

Now 4.6L/100klm is a very hard figure to get to. I mean REALLY hard.

You do have hills over there...don't you???

Where am I going wrong?