1crazy canuck

Driving in traffi, on the highway, off the highway, I started to look at my mileage #'s. I noticed that the car would either get 17.8 mpg or go straight to 18 mpg. NEVER 17.9 mpg.

I thought this was a little weird because it would get other .9's i.e 16.9, and 15.9, etc., but NO 17.9.

I even tried coasting a bit, and then it would go from 17.8, straight to 18, and back once I was on the pedal for a bit.

I didn't buy this car for the gas mileage, and mileage is not what my concern is for posting this -- I am trying to understand if there is a software glitch in my car, or a design error, or ?

Oh, an my car is an 05 C2S manual

Bob Rouleau

Probably a rounding error. Suspect it cvalculates liters per 100 KM and converts to MPG.

draxa

It's a disgrace. Porsche should be ASHAMED handing out cars with faults like this.

What next; electric mirrors that refuse to stop in the X6Y7 locus?

cole328

Personally, i'd get rid of the car. I thnk its a shame that the car will not give you such an exact reading. Also, on related topic, are we going to start again with the "Who ever uses their steeling wheel" posts? haha

haterade

dude, what is that bad-*** animal you got as your avatar draxa?

Jlangmd

You need to drive it harder. Get that mileage down to the 11 or 12 mpg where it belongs.

draxa

It's a labrador with some spliced-in tapir DNA - ergo, a labratapidor.

1crazy canuck

LOL...I like how you think...

before last week's eco experiment I was averaging 10.1 mpg

brendo

mine's stuck on about 12.8. with the US $ adn CA $ at parity, that should translate evenly

Sadiq

you get 18 mpg!?!? I've learned how to get about 15.2 driving conservatively

67FJ45

Doesn't the rounding error depend on the miles driven since the mileage calculator was last reset? I reset after every fill-up, and the increments my mileage gauge displays drop from 0.3-0.4 mpg with low miles since reset (say, around 10 miles) to 0.1 near the end of the tank.

Matt(inMA)

It must be the same computer Porsche uses on their clock... it can't keep time week to week....

Matt

cello

Hmmm, and all this time I thought it was the latest 'spy pic' of the Panamera

equiraptor

I suspect you're right.

13.1 liters per 100 kilometers is 17.95mumble mpg, which would round to 18.0. 13.2 liters per 100 kilometers is 17.81mumble mpg, which would round to 17.8. So they're calculating liters per 100 kilometers, rounding to a tenth, then converting to mpg, then rounding to a tenth, then displaying.

jcnesq

This is an annoying observation but I had to test it, so for the past two days I have driven like a grandmother and I have validated the OP's theory. In fact, the past two nights (lugging along in 6th gear), I watched my cumulative mpg on the tach display jump, from 17.4, to 17.5, to 17.6, to 17.7, to 17.8, to 18!!!, back to 17.8!!!. However, my current trip mpg on the NAV display did register 17.9.

I am now done with this test. Really, I don't care that 17.9 is "missing". Back to 15mpg or less!!!