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Old 02-11-2008, 10:56 AM   #1
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Gas Mileage!!!

Hey everybody,

I am loving my '97 boxster. (I have had it for 43 days!!!)

I recently had all the overdue maintenance done including a tire alignment from a great porsche shop, and it's now up to date mechanically.

I have one question about gas mileage. Granted it's been cold (25-35 degrees), but when I start it up, it just sucks down the fuel!! I did a test today.... when I started it up, I reset the fuel computer, and it was in the low teens and dropping in my driveway. I drove to pick up my daugter at school and then drove her home...... around 4 miles round trip. My final fuel usage was still around 15 mpg. Since it was a short trip, the engine really never made it all the way to full operating temperature. On the way, driving in a conservative manner, it got as low as 11mpg. It is a '97, 78Kmiles, Tiptronic transmission.

On a full tank of gas, combining local, highway, etc, I am getting around 21-22mpg. I am using 93 octane super-unleaded 10% ethanol (shell, exxon, etc) The former owner told me he was getting 24-25.

Anyway, does all this sound like normal cold weather MPG hits??

THANKS, in advance, for your help!!

Mark
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Old 02-11-2008, 11:57 AM   #2
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I would run a full tank and calculate it off the odometer and the actual gas usage. Those trip computers are notoriously incorrect. Not to mention the reason that it drops sitting in your driveway (I think) is that the gas mileage for 0 mph is 0 mpg. So it's taking that time at 0 mph into whatever moving average it uses to calculate mpg.

I think you'll find that if you look at your mileage when you re-fuel (by calculating it yourself), you'll do much better -- I get 21-25 in all city driving and closer to 30 (29.75 is the best I've done!) on the highway in my MY97 with 93 octane. Even with spirited driving, I don't think I've had an entire tank average below 20 mpg.

Hope this helps.

-Rich
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Old 02-11-2008, 04:01 PM   #3
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I check my gas mileage with every fill up ( sick obsession, lol). I have a 98 boxster. I consistently average 28-29 mpg. I would also suggest to check it off the odometer and dont necessarily trust the computer info.. My driving combines city and highway at almost 50/50 ratio.
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Old 02-11-2008, 04:41 PM   #4
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It depends on your city/highway ratio, driving style, and things like air flow (dirty or clean radiators?).
I have a '99 2.5L and I normally use 91 octane.
My average is about 20-21mpg 80 city / 20 highway. But when it is 50/50 I get about 25mpg. And on road trips 100% highway I have gotten up to 29-32mpg.
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Old 02-11-2008, 05:43 PM   #5
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Quote:
Originally Posted by gmboxster
I check my gas mileage with every fill up ( sick obsession, lol). I have a 98 boxster. I consistently average 28-29 mpg. I would also suggest to check it off the odometer and dont necessarily trust the computer info.. My driving combines city and highway at almost 50/50 ratio.
That is incredible! According to the computer's calculations over the past several months, we average about 23MPG combined. Ours is about 50/50 traffic to work and around town on the weekends.
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Old 02-11-2008, 08:00 PM   #6
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15 seems pretty low, but this is really dependant on driving style. The best ive done with my box - its a tip. . . was 28. 100% pure highway, cool day. The worst I've ever done was 24.3 - but that was still rural roads with a little bit of stop and go. I'd imagine in VA traffic I would get 18-20.

I too had had mileage drop in the winter on my other car - a civic. I've gone from 34-35 mpg in summer/fall driving to 24-25 in the winter. But the 24-25mpg on my civic was heavily in suburbs + lots of AC for defrost.
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Old 02-11-2008, 08:37 PM   #7
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Driving Style (incl. how much you idle, especially in Open Loop), Temperature, Tires, Tire pressures and their consistency, Humidity, Wind, Topography (live in the Plains or in hilly country), Driving mix, Road type and condition, Fuel quality and chemistry (fuel recipes change seasonally), electrical load (incl. battery condition), all have such an influence on Range (MPG) that comparisons of less than 4-5 MPG between 2 different cars are not very useful. I don't think you've described poor mileage at all. It may be your expectation which is off.

Last edited by Lil bastard; 02-14-2008 at 12:17 AM.
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