Very low mpg, help plz

[SC-986]

There seems to be a learning curve with these cars regarding engine rpm and shift points. When I purchased my 2002 base 4 yrs ago I averaged 17 mpg combined hwy/city. I am now averaging just over 21 mpg combined hwy/city.

More than any other car I've owned the 986 requires a period of time learning it's nuances before you can really experience it's performance capabilities.

I would reconsider your use of a K&N air filter. If too much oil is used it can end up on your MAF creating more problems.

[alm001]

Your method for sampling mileage is not very reliable. Different pumps will stop at different points, and with only putting in 4 gallons, a quarter gallon one side or the other could make a pretty big difference.

I track every tank, and fill when it gets low - usually before the warning. I try to use the same pump, but that's not always possible.

So far, with 5894 miles of ownership on my 2002 3.2
Average: 21.41mpg
Best tank: 24.08mpg
Worst tank: 17.71mpg

[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..?

[RandallNeighbour]

97 base boxster 2.5 here and I get 27 mpg on the freeway cruising at 70 and get this, 8 mpg at the track during DE's.

Biggest gap I've ever seen in a car I've owned.

[dghii]

My 2000S 6sp would get 17-18 around town and 28 on the highway.

[Steelepuls]

Tailwind, Sounds about right, I have an 01S, I get 15-18 in city driving with really bad traffic and have gotten 25 on highway to Reno.

[Ciao]

I get about 16-18 MPG city and if I'm lucky 20-22 Hiway; same as my 5,115 pound Toyota Landcruiser

[Smallblock454]

Hm,

i have to convert from Liter / 100 Km to mpg.

My average consumption is around 10 Liter / 100 Km, which converts to 24 mpg.

Lowest i got was around 8.5 Liter / 100 Km, which converts to 28 mpg.

If i push the car hard, it's around 12 Liter / 100 Km, which converts to 19.5 mpg.

On the Autobahn at higher speeds above 200 Km/h and more up to vmax it was around 15 Liter / 100 Km, which converts to 16 mpg.

Don't know what you do to get such bad mpgs in general.

[mikefocke]

It ain't a Prius, don't drive it that way. Once warm, an "Italian tuneup" every once in a while.

Of course, how fresh are the coil packs and plugs?

[elgyqc]

It seems to me first thing is to verify your calculation. Run through a full tank and I would double check the miles driven with a GPS to make sure the odometer is within reasonable limits.