89 Octane gave me an extra 50 miles
05-08-2008, 08:54 PM
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89 Octane gave me an extra 50 miles 1998 Trans Am convertible A4, lid, SSRA, FTRA, filter. 105k. 16" tires at 35 psi.
Checking between 2 back-to-back receipts of near identical 13.50 gallons of gas (93 vs 89 octane), I picked up almost an extra 50 miles with the 89 octane.
I usually use 89 octane when going on a long trip b/c there's less chances of redlight races.... just constant cruising.
However, I ended up WOT quite a bit and even raced a new Civic that was really asking for it. I was kind of worried of the gas. But didn't hear any pinging at all. The PCM definitely kicked it down to the lower timing table, because the car felt weaker. If I didn't race, it may have been 60 or 70 extra miles.
Also I drive with the top down almost all the time too, which is really bad for MPG. I heard that even with the windows down, it hurts MPG more than windows up and using A/C....with a convertible top down gotta be much worse.
Checking between 2 back-to-back receipts of near identical 13.50 gallons of gas (93 vs 89 octane), I picked up almost an extra 50 miles with the 89 octane.
I usually use 89 octane when going on a long trip b/c there's less chances of redlight races.... just constant cruising.
However, I ended up WOT quite a bit and even raced a new Civic that was really asking for it. I was kind of worried of the gas. But didn't hear any pinging at all. The PCM definitely kicked it down to the lower timing table, because the car felt weaker. If I didn't race, it may have been 60 or 70 extra miles.
Also I drive with the top down almost all the time too, which is really bad for MPG. I heard that even with the windows down, it hurts MPG more than windows up and using A/C....with a convertible top down gotta be much worse.
05-08-2008, 09:08 PM
#3
not sure what to say about the mpg thing,
but on the drag and windows down, the reason why windows down creates more drag and lower mpg is the wind blows in the windows then rams into the rear window of the car. On a convertible with the top down you don't have that rear drag, so really convertible with top down has less drag than a coupe with the windows down.
but on the drag and windows down, the reason why windows down creates more drag and lower mpg is the wind blows in the windows then rams into the rear window of the car. On a convertible with the top down you don't have that rear drag, so really convertible with top down has less drag than a coupe with the windows down.
05-08-2008, 09:31 PM
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not sure what to say about the mpg thing,
but on the drag and windows down, the reason why windows down creates more drag and lower mpg is the wind blows in the windows then rams into the rear window of the car. On a convertible with the top down you don't have that rear drag, so really convertible with top down has less drag than a coupe with the windows down.
but on the drag and windows down, the reason why windows down creates more drag and lower mpg is the wind blows in the windows then rams into the rear window of the car. On a convertible with the top down you don't have that rear drag, so really convertible with top down has less drag than a coupe with the windows down.
05-08-2008, 09:57 PM
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I have the same effect I get less range on a tank with 93 so I dont buy it anymore, There is a station here that sells 90, 91 and 93 so I usually opt for the 90 grade, I have been driving the car for a couple years and no problems even with 160K miles.
05-09-2008, 10:39 AM
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Unleaded has a higher alcohol content which allows it to absorb the water that condenses in the fuel tank.
05-09-2008, 10:42 AM
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Octane rating is just a detonation inhibitor.
05-09-2008, 12:19 PM
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on 2 trips going cross country, i experimented with 87 octane and it started pinging when accelerating out of the gas station, but ok when cruising at a steady speed. MPG was a little less than 89 octane. but 89 still got better MPG than 91-93. so the lower timing table is setup to run 89 octane more efficient than 87 octane i guess.
Last edited by mark306ci; 05-09-2008 at 12:29 PM.
05-09-2008, 12:22 PM
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yea, if you want the full performance of the car.
but if you can live with less power for better economy, the PCM's lower timing table can accommodate that. it's there for purposes such as getting wrong gas, bad gas, or in cases where higher octane is not available.
but if you can live with less power for better economy, the PCM's lower timing table can accommodate that. it's there for purposes such as getting wrong gas, bad gas, or in cases where higher octane is not available.
