Very low mpg, help plz

[Smallblock454]

OK, you really use 91 octane fuel? The ecu is designed to 98 octane fuel over here in Germany (fuel type is called Super Plus). Don't know if the US cars do have another ecu.

The fuel is to expensive? Well, over here in Germany 1 litre Super Plus is around 1,40 Euro at the moment. And that is a very low price compared to a year ago where we were at 1,80 Euro a litre. 1 gallon is 3,7854118 litre. So at the moment one gallon Super Plus would be 5,30 Euro, or 5,85 USD.

16 MPG = 16 miles per gallon

I have a Boxster S MT.
Fuel consumption:
Lowest was around 8 litre / 100 Km -> MPG = 29.40
Highest was around 16,5 litre / 100 Km (around 220 - 260 Km/h on the Autobahn all the time) -> MPG 14.25

The average fuel consumption of my car is at 10,5 litre / 100 Km which is 22.40 MPG

Bought the car new in 2003.

Regards from Germany
Markus

[alm001]

Originally Posted by Smallblock454

OK, you really use 91 octane fuel? The ecu is designed to 98 octane fuel over here in Germany (fuel type is called Super Plus). Don't know if the US cars do have another ecu.

The fuel is to expensive? Well, over here in Germany 1 litre Super Plus is around 1,40 Euro at the moment. And that is a very low price compared to a year ago where we were at 1,80 Euro a litre. 1 gallon is 3,7854118 litre. So at the moment one gallon Super Plus would be 5,30 Euro, or 5,85 USD.

16 MPG = 16 miles per gallon

I have a Boxster S MT.
Fuel consumption:
Lowest was around 8 litre / 100 Km -> MPG = 29.40
Highest was around 16,5 litre / 100 Km (around 220 - 260 Km/h on the Autobahn all the time) -> MPG 14.25

The average fuel consumption of my car is at 10,5 litre / 100 Km which is 22.40 MPG

Bought the car new in 2003.

Regards from Germany
Markus

Octane ratings are calculated differently here in the U.S.

91 octane in California would be 95 to you.

[jb92563]

For short 5 mile trips with a couple lights I think 16mpg is normal.

The first couple miles the engine is still warming up and throw in a couple lights and it just plain lukewarm city driving.

My drive in the morning is 15 miles, 6 miles with 16 lights city driving and 9 miles of highway at 70+mph.

I get 230 miles on 12 gallons(91octane) which is about 19mpg city/hwy.

My computer says about 16mpg in the city parts.

On pure Hwy cruising I have seen as high as 30mpg on the computer in 6th gear @75mph.

[Tailwind]

I "filled" my car for the first time and I stopped when it clicked off at 13 gal. Had 200mi on the trip readout, so 15.4 MPG This was mixed driving. Around town, I'm at or below speed limit, keeping the rev's around 2.4K. Next fill I will try to squeeze ~16 gallons in (I went onto reserve right after the dentist visit and drove about 25 miles).
I plan to clean my engine and do a TB/MAF clean. I have fresh plugs. I'm going to take the advice given here about shift points.

[Gilles]

Tailwind, out of curiosity, what is your tire pressure..?

[Tailwind]

Originally Posted by Gilles

Tailwind, out of curiosity, what is your tire pressure..?

29/36, as stated on the pressure label. Good thing I checked the spare. Apparently previous owner didn't; it had 2lbs in it. I aired it up to 60.

[Tailwind]

Second tank, 17mpg from ~ 105mi city, ~50 fwy.
I need to check the air filter, and track the fuel trims.

[Tailwind]

Just getting on the freeway, the reserve light came on. After a 35 mile round trip, the needle was half way between Empty and Positively. 14 gal fill with 276 on the Odo = 19.8MPG mixed driving, more freeway this tank.