Is this normal? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Viper5 · 06-01-2010, 11:56 PM

Ever since I've had the car (2 years) I've been only getting 13-15 mpg in the city according to the OBC. I know it's a sports car and all, but is this right? I've replaced my air filter a few months ago. I don't remember ever replacing the fuel filter though. So is this normal?

Lucky · 06-02-2010, 01:43 AM

Seems low, but if you drive it hard it could be accurate. Have you figured mpg by hand? Maybe the OBC is way off?

As a data point, my S gets right around 20 (calculated by hand) in mixed driving -- my worst tank has been 19.5. Best around 21. I don't have the OBC, so I can't comment on its accuracy.

Johnny Danger · 06-02-2010, 02:13 PM

That seems like extremely low mpg .

Tranlm · 06-02-2010, 02:22 PM

Same here, though I calculate my MPG out manually when I fill up on gas. Its not hard actually if you just remember to reset the odometer every time you fill up.

Quote:

Originally Posted by Lucky

Seems low, but if you drive it hard it could be accurate. Have you figured mpg by hand? Maybe the OBC is way off?

As a data point, my S gets right around 20 (calculated by hand) in mixed driving -- my worst tank has been 19.5. Best around 21. I don't have the OBC, so I can't comment on its accuracy.

Pat · 06-02-2010, 02:40 PM

Quote:

Originally Posted by Viper5

Ever since I've had the car (2 years) I've been only getting 13-15 mpg in the city according to the OBC. I know it's a sports car and all, but is this right? I've replaced my air filter a few months ago. I don't remember ever replacing the fuel filter though. So is this normal?

Something is way off. You should be getting 30% better mileage.

rick3000 · 06-02-2010, 02:48 PM

That is low, something is wrong. I get about 18 city/28 highway, up to 34 on road trips. It could be the OBC, and being a Base or S and driving style plays into it, but not that much.

My first thought would be to keep it simple and disconnect the battery then reconnect it. That will reset all of the computers, and may help the car recalibrate itself to be more efficient. My next move would be to clean the throttle body.

http://www.pedrosgarage.com/Site_3/Clean_the_Throttle_Body.html

sb01box · 06-02-2010, 07:49 PM

My car is 01 5 speed.
Use it for daily drive, 14 miles round trip. 10 freeway, 4 miles of city & may be
couple of 200 mile trip per month (freeway).

I usually write down the odometer reading with each fill up.
I've graphed mpg and cost per mile over 40K miles of ownership.
did MAF and throttle body clean but no noticeable change in mileage.

,

Jake Raby · 06-02-2010, 08:06 PM

The main contributing factor to poor MPG is bad lifters.. I have seen an engine get a new set of lifters and pick up 10MPG when it was only averaging 14 MPG on the highway... (extreme case)