lower octane gas = better for high altitude?
03-08-2008, 02:45 PM
#1
2nd Gear Member
Thread Starter
Join Date: Apr 2007
Posts: 208
lower octane gas = better for high altitude?
myGT lives at ~1 mile above sealevel,totally stock and has always beenon a diet of 87 octane gas (RTFM).
The other day I accidentlly filled it up with 85 gas (same conoco station i usually get 87 at) and it seems like the car is actually runningsomewhat better (i expected quite the opposite). Whazzup with that?
+1:at lower altitudes they don't even have 85 octane (here we have 85, 87, 91) so there appears to be a tendency for
lower altitude <=> higher octane. anybody care to comment on that?
it is tempting to save 15-20 cents/gallon with these gas prices...
The other day I accidentlly filled it up with 85 gas (same conoco station i usually get 87 at) and it seems like the car is actually runningsomewhat better (i expected quite the opposite). Whazzup with that?
+1:at lower altitudes they don't even have 85 octane (here we have 85, 87, 91) so there appears to be a tendency for
lower altitude <=> higher octane. anybody care to comment on that?
it is tempting to save 15-20 cents/gallon with these gas prices...
03-08-2008, 04:05 PM
#3
1st Gear Member
Join Date: May 2007
Location:
Posts: 106
RE: lower octane gas = better for high altitude?
I hope this helps...I found it on-line a while back.
In the Rocky Mountain (high altitude) states, 85 octane is the minimum octane and 91 is the maximum octane available in fuel. The reason for this is that in higher-altitude areas, a typical combustion engine draws in less air per cycle due to the reduced density of the atmosphere. This directly translates to reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a car with a carburetor that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains
In the Rocky Mountain (high altitude) states, 85 octane is the minimum octane and 91 is the maximum octane available in fuel. The reason for this is that in higher-altitude areas, a typical combustion engine draws in less air per cycle due to the reduced density of the atmosphere. This directly translates to reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a car with a carburetor that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains
03-08-2008, 05:01 PM
#4
2nd Gear Member
Thread Starter
Join Date: Apr 2007
Posts: 208
RE: lower octane gas = better for high altitude?
ORIGINAL: rjb
I hope this helps...I found it on-line a while back.
In the Rocky Mountain (high altitude) states, 85 octane is the minimum octane and 91 is the maximum octane available in fuel. The reason for this is that in higher-altitude areas, a typical combustion engine draws in less air per cycle due to the reduced density of the atmosphere. This directly translates to reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a car with a carburetor that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains
I hope this helps...I found it on-line a while back.
In the Rocky Mountain (high altitude) states, 85 octane is the minimum octane and 91 is the maximum octane available in fuel. The reason for this is that in higher-altitude areas, a typical combustion engine draws in less air per cycle due to the reduced density of the atmosphere. This directly translates to reduced absolute compression in the cylinder, therefore deterring knock. It is safe to fill up a car with a carburetor that normally takes 87 AKI fuel at sea level with 85 AKI fuel in the mountains
