Being for the benefit of Mr. Kite,

I am curious if Honda does anything special in the higher altitudes of Colorado to tweak the engine or if the ECU & MAF make adjustments based on the leaner air.

One would expect you to get a little lower gas mileage at altitude...

Interesting,

Michael

 

I don't think they do anything different. I would speculate that it is all computer controlled. One thing to note, the lowest grade of gasoline here in this area is 85. The owner's manual calls for a minimum of 87 octane. Because of this, I have to use the mid-grade gasoline. Any thoughts on this? I have had a fun time playing the mpg game off and on. I can see that with a little bit of attention, I can do better than epa. This is something that is nearly impossible for me to do in my 2005 Honda Odyssey Touring, but it was easy for me back when I had a 2002 Honda Accord EX manual. Anyway, this sure beats the FE of the Subaru Outback (24mpg) that we traded in.

 

I would contact your dealer and also Honda in Torrance. You probably will have to use 87.

Aparently, 25 years ago, studies were done at altitude with carbureted engines in high altitude regions of the country and it was determined that for every 1000 feet in elevation, Octane could drop by 1. So Colorado and nearby states get 85 octane. Since there are no laws on the books in Colorado, nor nationally, dealers sell the lower-cost (to them, not you) octane fuel. With today's cars, and fuel-injection, 87 is the minimum recommended by all manufacturers.

If you do use lower octane, the engine's ECU & MAF will compensate, however your mileage and power will be reduced and it is possible (however unlikely) that you could damage the engine over time.

Honda even mentions in the owner's manual that you should use major brand detergenated fuels and not off-brands for risk of fouling the fuel filters and lines as well as possible damage.

 

I doubt it was the Lord who told you to by a Hummer, but as SNL's Church Lady used to say, perhaps it was Satan!

What would Jesus drive? I'm biased, but I think it would be a HCHII !

Aneil

 

I used my own gift of reason to determine that the HCHII was the best car for me and my family. To me, it seems silly to try to justify our actions by arguing that a dead man would have done the same thing.

 

Our engine runs a 10.8:1 compression ratio. We are on the outer limits of 87 Octane fuel being good enough for our car and close to the edge of detonation.

Knock sensors of course help thwart this but can only do so much.
Thin air will not burn as fast or as easily as it does in lower elavations.
The higher the octain, the slower the burn and vice versa.

That all being said, 85 octane is meant to be the equivilent to 87 based on your altitude. At your next fill up, I would wait until you are nearly empty (last bar has disappeared from fuel gauge) and put $5 of 85 octane in the car. This will be a minimal amount to see if you hear detonationd (pinging under moderate load). If you do indeed hear detonation, stop at a service station and top the rest off with mid grade. This should counter the lower octane and get you detonation free. If you hear no detonation, top it off with 85 and roll on. Just make sure you get at least 20 to 30 miles on the 85 octane when you test it so as to insure the old gas has cleared your fuel lines.

Detonation is not a good thing. It generally will not hurt your car if it happens every now and then. If it is an ongoing or persistant issue, you need to get the car to Honda as detonation can destroy your valves and damage your pistons.

Edit:
Too high of octane coupled with thin air will result in lower spark plug life as they will collect build up from running too rich and you will degrade the longevity of the engine as well as get lower MPG.

 

Just a guess here, but I'd say that continuous detonation would set a check engine code (long before any damage is done!). Reason? If the knock sensor's signal cannot be corrected by retarding timing, then the controller will assume the sensor has a fault and set the code.

 

Interesting discussion.

 

It was joke, Rev! Besides Jesus would have probably stucked to a donkey.
Aneil

 

I'm quite surprised to see that buying a new HCH II csn be so much cheaper in the States (Seattle) compared with here (Vancouver, BC) in Canada. Our cost tax included is about Can $30,000.