I've owned my 03 Touring for about 2 months now and just as an experiment, I always let the gas tank run down near empty, refuel fully, and calculate the mpg manually and I usually don't get more than 22 mpg and roughly 400 miles. According to the computer, it says I'm getting 24-26 mpg with a range of about 420 miles.

Trust me, I am not complaining 22 mpg on 400 miles on one tank is not bad at all, I just wish the computer would be more accurate (or honest, depending on one's POV; also, I know that the Z isn't the only car that inflates the numbers either). This just goes to prove that manufacturers like to tweak the computer to trick drivers into thinking that they're getting more value than they really are.

 

hmmm. I just did a 1100 mile road trip. The trip computer ranged from 27-24 mpg. Guess I should look into this to see if it's accurate.

 

The mpg gage tells you what you are getting now at the current mph. If it reads 20 mpg, it does not mean that you were getting 20 mpg yesterday or the day before.

When you do the fill-up and arithmetic, of course you are calculating average mpg for the entire tank: different numbers - different purposes.

 

I think my mileage is accurate but when I fill up my dte says 222 which is not right. Has anyone else had this problem.

 

I always reset the MPG after every fill up. When you reset it, as Davidv said, the MPG readout tells you what your current mpg at the mph you are driving, but then it starts averaging it out. Toward the end of my tank, the MPG readout has been pretty accurate as to how much gas I have left. The DTE, I ignore because it does this, --- , when I still have 50 miles left.

 

Thanks for the info marco mendoza

 

400 miles to a tank???? Wow I must have a heavy foot or problem. I do 50% city and 50% highway and I get approx 330-350 miles to a tank. Also my cpu reads 20.3 mpg.

 

man i gotta stop shiftin at 6k.....been gettin 16mpg about 270 a tank

 

Is there any way to modify the thing to give us instantaneous mpg?

 

Doubt it. It has to average samples in order to get an accurate reading so I'll answer with no.

 

I'd say, the only way would be to reset the MPG gauge every couple of minutes to reduce the number of times it recalculates the average.

As for DTE and the AVG mpg gauge, I think its fairly accurate.
My Z averages (manual calculations) around 24 MPG city, but I can't remember how close it is to what the gauge says. I just filled up my tank, so I'll have to do a comparison at the my next fill up, but I think the gauge or my calculations aren't off my by no more than 1 mpg. We'll see.

 

Mine was quite accurate until I twin turboed. Now it is off.

 

Call me a wuss but I baby my Z. I try not to get above 3k rpm and I skip gears when I shift (1st to 4th to 6th, etc.) and I don't do monster acceleration at stoplights. I guess that plays some small factor in getting 400 miles on a tank.

 

Ok, you are a wuss. Im am sad for your Z as it lives the life of a toyota yarris. I say pound the z, shift at 6200, get 220-270 miles a tank, and enjoy having a car that can do what a z can do. I hope your adult diapers dont break the next time you are going 40 mph in 6th gear.

 

I reset mine after a fill up and kept my reciepts once and it was less than .5 mpg off so from now on I assume its correct... don't use dte much

 

I do all city driving and I've never averaged over 17.5 MPG on a full tank. I also don't drive it like a grandmother, so I'm not too upset about it.

1st to 4th to 6th? You should put panties on your exhaust.

 

Why do people buy a z if their going to get 400 miles on a sports car..... lol get a ****in prius. Now I'm not saying drive like an idiot and put other lives in danger but getting 400 miles on a "sports" car is just bizarre

 

I monitor my gas mileage pretty closely, so I think the mpg readout is a pretty handy tool. Regarding 'instantaneous' gas mileage reading, I am inclined to believe that the only time it gives you an exact gas mileage is the first reading after it's been reset. After that, each readout should be an average.

At any rate, I have been calculating mileage by hand (using the same pump at the local gas station every fill-up) and my results are very close to the car's readout. Of course I wish the mileage was better, but that's a different story...

 

I have about a 40 mile commute to work each way. I do about 75-80 the whole time in 6th. I fill up on Monday and it lasts me till Friday. I get just over 400 miles per tank with the JWT popcharger. The DTE is way off considering we have a 20 gallon tank. I've only had to fill the tank 17 gallons at the most. That is only 23-24mpg. I get anywhere between 22mpg and 29mpg on the weekdays, but it's all highway, only 1.5 miles of sidestreets. On the weekend I drive her the way she wants to be driven, which is why i need to refill on Monday. Sometimes twice a weekend.

 

man...shifting from 1 to 4...doesn't that really slam your RPM? isn't that bad for your car? at least shift to 2, then to 4....if you're saying you "baby" your Z and shift 1 to 4, does that mean you shift from 1 to 4 RIGHT at 2000/3000 RPM? man, that is BAD for your car to drive in high gear at such a slow speed/RPM, you're hurting your car more by gunning it in such a low RPM (because if you're accelerating from 3-4 mph in 4th gear, you will have to floor it in 4th, otherwise it'll choke)...unless you're maxing out your 1st gear, and then shift to 4, in that case, you're not really babying your Z at all then...

In a Porsche, if you do not gun it often, you will clog up your pipes and your car will start coughing after awhile...Porsches are meant to be driven hard to clean out their internals, does anyone know if the Z is like that? probably not egh?