Fueled up in Salmon Idaho and realized after the fact that I had filled with 85. Now, I have always been under the impression that higher octane at higher elevations is better and helps prevent engine knock. However, upon googling, it seems the opposite is true and 85 is recommended... Learn something new everyday I guess.
haged333
Newer rigs have so many sensors anymore I think they compensate really well for altitude and driving conditions. If i had a rig that only required 85 octane that's what I would use in it and let the knock sensors do their job.
If all you driving is at "altitude" continue to use the 85 unless you vehicle manufacturer says no. Other wise if you have a choice go to the 87 octane that is normally used at sea level to about 4k feet. The sensors may adjust to the 85 but it can still cause problems if you are going up and down the mountain so to speak.
Now if you have one of those little 4 cylinder turboed engines that is another matter. Some require 91 octane but will run on 87 with less power. I would never put 85 in them.
Now if you have one of those little 4 cylinder turboed engines that is another matter. Some require 91 octane but will run on 87 with less power. I would never put 85 in them.
Engine compression ratio determines octane need. Low compression ratio = 87 octane. High compression ratio = 89 or 91 octane.
Your EFI engine will compensate for altitude. If you have a carb then you have to adjust the carb lean/rich fuel mixture.
Your EFI engine will compensate for altitude. If you have a carb then you have to adjust the carb lean/rich fuel mixture.
Air being less dense at altitude produces fewer PSI on compression so 85 is fine. 87 would be better.
85 works fine in our motorhome 92 460 with smog 5000 to 8000 foot elevation. i thought it would create issues but it was fine.
Modern engines have sensors to prevent pinging. performance will suffer. Many modern engines have compression ratios that should require high octane but people have no idea. The 6.2 vortec for example, 11.5:1 would be a singing machine on pump gas without the electronics.
To speak directly to your question, higher elevation requires less octane.
To speak directly to your question, higher elevation requires less octane.
Any time the knock sensor goes to work, performance suffers. Cars these days are so well insulated against noise we canāt hear whatās going on inside the motor. The anti-knock usually kicks in before the sound becomes audible anyhow. I put 87 in my Pathfinder one time just for kicks. The old get up and go, got up and went. Could really feel the loss of power at full throttle. Playing around with fuel to save a few cents isnāt worth it.
On one trip back to Wisconsin to pick up a couple of pups we took the Pathfinder since weād be transporting pups back to Oregon. It appeared a lot of the fuel we got was being sold as premium but was a lesser grade. The old fuel gauge would start dropping soon after fueling up at some outlets. Other times the mileage was actually what one would expect out of premium. I ran a few tanks of 92 E-0 because it was starting to become available. It didnāt appear to have any advantage over 91 E-10. 92 E-0 is quite common these days. It would be interesting to run it in a motor set up for 87.
On one trip back to Wisconsin to pick up a couple of pups we took the Pathfinder since weād be transporting pups back to Oregon. It appeared a lot of the fuel we got was being sold as premium but was a lesser grade. The old fuel gauge would start dropping soon after fueling up at some outlets. Other times the mileage was actually what one would expect out of premium. I ran a few tanks of 92 E-0 because it was starting to become available. It didnāt appear to have any advantage over 91 E-10. 92 E-0 is quite common these days. It would be interesting to run it in a motor set up for 87.
Pinging = Detonation
Detonation =A hammer šØ hitting the top of the piston .
You can listen to it and now you know this ,you can worry and sweat a hole in a piston is in the future or Ear plugs šš»
Octane ,timing and load on engine ,either detonation or Not .
Detonation =A hammer šØ hitting the top of the piston .
You can listen to it and now you know this ,you can worry and sweat a hole in a piston is in the future or Ear plugs šš»
Octane ,timing and load on engine ,either detonation or Not .
the higher the octane, the longer the detonation phase in an ICE.
Many people think high-octane gasoline is more powerful than low octane gasoline. This is not true. The energy produced from a gallon of high and low octane gasoline is almost the same. Any minor variation depends on what additives are used by refiners and blenders. The key features of high-octane gasoline are a higher ignition temperature and a slower burning rate.
I have found that higher octane helps the performance of the engine at higher elevations.
Many people think high-octane gasoline is more powerful than low octane gasoline. This is not true. The energy produced from a gallon of high and low octane gasoline is almost the same. Any minor variation depends on what additives are used by refiners and blenders. The key features of high-octane gasoline are a higher ignition temperature and a slower burning rate.
I have found that higher octane helps the performance of the engine at higher elevations.
Interesting that this discussion has not gotten into the ethanol situation. A number of years ago I had my F350 v10 in Wyoming and none of the gas there had alcohol in it. I got close to 15% better mileage even with 85 octane. The alcohol is supposed to help clean up the air pollution problem but when you burn more fuel using it you produce more CO2 so what is the net gain?
LGB, A gallon of benzine (gas) has much more energy in it than a gallon of ethanol. So, you will get about 15% farther per gallon on straight up benzine than gas/Ethanol mix.
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