So I have been running a few tests on my 997tt and the economy is down the tubes. In the city I'm averaging around 12MPG or 19.8L/100km.

This seems outrageous as I'm driving the car normally, light footed, and not in sport mode. I should mention the tune I have uses stock maps in normal mode, so it can't be that.

Are there any recommendations of what or where to look at to figure out why it's chewing through fuel at such a rate?
Any thing I could check with a durametric - I have the cable?

I should mention the car has 92,000km on it, runs perfectly other than being an absolute pig on gas

 

How long have you owned the car? Has all the air and gas filter been changed? I am getting about 15-16L per 100

 

I'm doing about 15 - 17mpg depending on driving conditions. 2009 6 speed no mods 31k miles. Seems fuel consumption is very high on your ride. Its almost approaching the ridiculous 9-10mpg my 2007 M5 does!

 

I get between 17-20l/100km in the city, only bright side is a collegue who sees 30l/100km in his S6.

 

Step1:

Insert key in ignition.....Step on Brake.....Turn key to start position ....wait until car starts....then release key.

Step two:

Drive car to Mitsubishi delaer and purchase an i-MiEV.

Step three:

Enjoy gas savings and miss the hell out of all that power

DC

 

Yup, all services are up to date and then some.
Was wondering if ti may be something internal in the engine. It's an '07 with quite a few miles on it. Was wondering if there are any tale tell signs I could pick up with a durametric?

Hahaa - I'd rather end up walking then that option!

 

i always laugh when i see threads like this... you drive a modded 997TT.. and your concerned about gas milage ? really?

go get your self a prius. end of story...

 

Or he can add this mod to the car:



In all seriousness, the only thing that I found to influence mileage on my 997TT was tire pressure, which yielded maybe 1-2 miles per gallon if I was at the drag strip.

 

At highway I can get decent milage, but never in the city, as others stated live with it or get something else as a DD.

 

Someone woke up this morning and fancied himself as a smarta.s.s :P

When I'm not driving back and forth to work - a heavy foot and lot's of gas is no concern.

However... when I'm trying to be economical, the fact is it's not as reflected in OEM standards, which has me a little concerned - if it could be a sign/symptom of something else?

Seriously though, other than the obvious, is there nothing else one can do to diagnose?

 

Based on my experience with my Turbo gas mileage can go really bad really quickly with aggressive driving but can take a long time to recover with even the most economical driving.

If you hammer the car around a bit and then think you are going to get the mpg from the teens back to the mid-20's you are in for a disappointment.

About the only way I can get my Turbo's gas mileage to the low to mid 20 mpg range (26mpg to 28mpg is about the best I have managed without resorting to coasting down long mountain grades) is to when after I fill up the gas tank and reset the on-board computer is to drive the car very easy. I can cruise at 70mph, 75mph but any heavy throttle and there goes the gas mileage. A few seconds of indiscretion like a hard acceleration along a long nice freeway on ramp can take scores of easy driving miles to recover from.

If I drive around town after the fill up/OBD reset, forget it. I'm lucky to see the high teens and that has to be a good day.

If the CEL is off and the engine behaves ok there's probably nothing wrong.

Check tire pressures. Low tires can affect gas mileage. If it has gotten cooler where you are the tires may be under inflated.

Also, cooler weather alone -- ignoring any effect it may have on tire inflation pressure -- affects gas mileage. The engine is cooler, the oil more viscous, so there is a bigger parasitic load on the engine until the oil warms up and in cooler weather it may not get as warm as it does in the middle of summer.

In cooler weather generally the engine spends more time idling due to letting the windows clear/defog and with heavier traffic average speeds around town are down and this adds up to lousier gas mileage.

Oh, some regions switch to a different blend of gasoline which can also affect gas mileage and not in a good way.

 

If your car was OEM then guys probably wouldn't answer as above but it
looks, from your signature, like it's putting out 135 hp higher than OEM.
I had a 2005 TT with exhaust and tuning and got about the same, better
than my current, about to be traded, 650 hp Viper.

 

Check tire pressure
Check air filter
What kind of gas are you using?
Have the plugs been changed?
Are the coils good?

If everything is good I would start to look at the mods like the tune.

 

I have modded vtgs etc.... and I think my average mileage is similar to when the car was stock. Mainly highway driving but a bit of city. Some launching and bursts of speed and I get about 400km/tank. PurePorsche, did your mileage suddenly change or has it always been "bad"?

Lol at the comment about the Audi S6. I just got an A6 and it gets great mileage when I take it to work - mainly highway. When my wife takes it to work the mileage plummets! Not just her lead foot I presume. The city driving really makes a difference.

I was at the track 2 weeks ago and went through 2 tanks of gas for a total of about 200km, lol. Just like the review in Car and Driver stated, "it sucks down the dead dinosaurs like a Viper with a hole in the gas tank".

 

O2 sensors could possibly cause this (pre-cat) but it's pretty unlikely that they would be far enough out of spec without throwing CELs. Sounds like something is definitely up though, I get better mileage than what you're reporting on E85 and I have a heavy foot