The mileage computer may not be accurate. The graph shows my onboard computer indicated mileage vs. Actual Mileage (as calculated by dividing the mileage travel between a fill-up by the number of gallons (as indicated by the gas pump register). The data shown is for 72 tank refills (21,850 miles & 956 gallons).

Basically, computer mileage is 1.6 mpg higher than reality. The equation for my old 2002 996.2 was y = 0.9936x - 0.4759 (essentially the computer was reading ~0.5 mpg high)

 

I'm kinda glad to discover that I'm not the only one that tracks this stuff methodically. I thought it was just the nerd in me.. But maybe what I am discovering is that Porsche owners are a technical, analytical lot

Around town driving with some hwy mixed in, I get around 22 - 23 MPG; usually fill up around every 4 weeks.

Last Summer, we did a road trip from Denver to Cincinnati; think I got on average around 31 MPG with purely non-stop hwy miles. Not sure if fuel grade/octane rating had any sort of additional impact on those figures- OH gets 93 octane (lucky ducks) while here in CO, we get 91. I can get a 93 octane average by mixing in some 100 octane to the tank, but the cost to do so doesn't make sense.

A lot of people are quite surprised to hear that a sports car can achieve these kinds of fuel econ figures

 

Only driving I now do with the car is curvy, back-roads type driving and I think I average under 15 mpg (need to check to confirm). I like running through the gears and always try to give the car an italian tune-up whenever I take it out (after getting up to operating temps, of course)... mpg is not even on my list of considerations with the car.

When I did longer highway trips I was averaging around 27-28 mpg.

Not bad really. I think I average something like 8 or 9 mpg in my Viper.

 

I am getting 10-11-12 mpg in my 2005 911. I am curious why so low. This is in town driving.

 

I would expect that if:
1. Trailering a 997, with a 997.
2. Problem with something in emissions system like bad O2 censor.
3. Parking brake on.
4. Driving around at 4k rpm cruising, because it sounds better.

 

13.4. Seems about right for a car I drive purely for pleasure.

 

my average has been pegged at 16.8 for so long, I just figure it isn't working. The mileage av. is always around 30 too. LA.
a few times I have seen better mileage for long freeway trips. Sometimes, I have seen it worse on mountain drives.
However, I noticed I always close in on over 280mi per tank and under 300mi per tank before the light comes on.
I do not wait to fill up once I get the warning, so I think I would break 300 in a tank if I did.

 

Current average mileage since purchasing from 1st owner (with dealer CPO) over last 24,820 miles has been 23.39 mpg. Excluding a DE weekend, lowest has been 18.9, highest 28.9 (actual mpg, not what the computer said)

 

Mine is at 12.9 for 10k miles. I reset it the day I purchased and have not touched it since.

 

With these gas prices, I don't think it matters what your mpg is... but I'm averaging around 21-22.

 

I get 18 +-.5 but I drive almost exclusively in sport mode. If I drove in normal mode I would get better but I can't stand the lugging...

 

Pretty consistently 16.1 in my 2006 997 C2.

 

12-13 mpg in purely city driving in hilly San Francisco. 2008 C4S