Charolastra

Hi Guys,

I just got my 2007 997.1 C2S several months ago, and have been loving every second of it thus far* (*my first Porsche). The one drawback I'm finding, however, is that the real world MPGs I've been getting have been pretty bad compared to what I was expecting. Over three tanks, I have averaged 16.9 miles/gallon, in a 50/50 mix of suburban/highway driving. I was expecting something closer to 21 mpg avg/tank. Is there anything wrong with my car? What has everyone else experienced?

Some additional info on my circumstance:

-car is driven on michelin PS2 tires
-avg. weather temp is 45 degrees F* (*I live in the Washington DC area)
-car is 6MT, w/ Sport Exhaust
-I normally shift at 4k rpm* (*occasional high rpm shifts). I am not driving it like I stole it.
-onboard computer is being cross-referenced w/ my manual mileage calculations upon refueling, and both numbers match up.

I really have no idea why my real world mileage is so poor. Can anyone provide some feedback/insight/suggestions as to what may be causing this? Many thanks in advance!

Aerokitted

Your mpg sounds about right.

You live in an urban area so your readings will fall closer to the rated 16mpg than the hwy 24mpg. Even on the highway, you're likely to be sitting in some sort of traffic on avg esp if commuting to and from work.

My model is 15/22 and I typically average 16 on premium fuel and the tires inflated at the factory recommended specification.

My gut tells me nothing is wrong with your 911. Enjoy it.

Ken968

That number seems low. You didn't say how many miles are on the car but you should consider a tune up (plugs/filters/oil etc). Also I am not 100% sure but if you are using low octane low quality gas, I think that may cause a decrease in mpg also. I always run Premium in my porsche but I know if I don't put premium in my BMW X5 the mileage goes to crap. Im sure others will chime in.

Ken

Da Hapa

My 2008 C2S with 6 speed manual, X51 headers and PSE exhaust averaged just over 19 mpg using actual gallonage and not the trip computer (which was always optimistic). My usual tank was mixed driving of probably 60% streets/40% highway. Highway driving here in S.CA is settign the CC at 75mpgh.

I would routinely see mid to high 20's on the freeway but low teens or single digits around town.

ELUSIVE

My average is about 17 for all purpose driving. I'm about 70% streets and 30% highway.
2006 997S

Edgy01

Mine is very similar. 06 S with PSE. I suspect just because of the PSE I run it at higher RPMs and thus pay for it at the pump! But, that's okay!

allegretto

your mileage is way too high

You're not having enough fun!

Alan C.

I averaged about 20-21 in my 09 C2S manual with about 60 highway 40 city. My 11 GTS PDK is getting around 18 with the same mix. The GTS just turned over 1600 mi.

duke92

Me--lead foot, all city = 14.1

USMC_DS1

I stopped checking since I've been driving mine at 4-6K RPM in sports mode. 16.9 mpg sounds about right in the city. I've seen mid-20's on long highway treks when I've tried to hyper-mile just for see what it could do.

socalbusdev

2008 C2S with 22K mi. Mileage sounds right.

Charolastra

Thanks for the feedback/insight guys, it is reassuring. A few things I forgot to mention:

-The car has 42k miles on it. So it is already broken in.
-All the gas I've filled it up with has been premium (93 octane and above, if they have it), however, I've noticed that all the gas I've used has had 10% ethanol (which I've read is less efficient than dino oil).
-plugs/filters/oil were all changed at 40k when I bought the car. Car tire pressure is also running at factory spec (as per TPMS and manual read).
-I have tried driving an entire tank w/ PSE on, and an entire tank w/ PSE off, and there is no difference* (*not that I'd expect there to be, but I'm just trying out all possible variables here).

I would expect that mpgs will increase once the weather gets better, no?

Also, when I first bought the car, the first tank was driven w/ a "drive it like you stole it" mentality, yet the mpg/tank still averaged around 16.0. So it looks like the car is just begging for me to drive more aggressively....

T951

08 C2S about 20k....my driving is sadly 90% highway 10% other/fun. I looked and I am at 20.9

Lot's of cruise control set at a normal driving speed.

docfink

I agree.

Palmbeacher

There it is. Here in FL 10% ethanol is mandated. Purely special-interest politics to fatten some cat's wallet. They say it cuts mileage about 3%, which when translated from politican bullsh!t means at least 10%.

My 3.6L standard shift gets 16mpg in mostly suburban driving, revs 3-4K. Flat roads, avg 25mph (mostly 35-45 mph limits with idling at stoplights about every mile), temps typically >70F. On the interstate doing 70-80 it'll do 24mpg.

One thing I found is that it doesn't seem to save fuel to upshift early and drive <2K rpm even though there's plenty of torque to do it w/out lugging. I get the same mileage keeping the gear where the revs stay between 2,5 and 3K, and I get better lube on the IMS bearing.

And every once in a while I open it up. It's good for the car, and great for me