Average MPG

[acgtrider]

450 mile round trip to Northumberland and back my 2.7 facelift 986 gave a calculated 38mpg, dads prefacelift did 39mpg calculated on a 240 mile round trip. They can be efficient. I seem to average 25 on my commute though. 

[Stuart21UK]

I managed 17 mpg on the round trip to the local shops yesterday...even put the sports exhaust on to make it more worthwhile

[rowbos]

37 minutes ago, Stuart21UK said:

I managed 17 mpg on the round trip to the local shops yesterday...even put the sports exhaust on to make it more worthwhile

Fair play 😬

[BTM520]

I can't believe this thread is even up on this site...drive the car and drive it hard (once warmed up of course), enjoy the noise and have a smile on your face whilst making the car noisy and eating corners. 

[GmanB]

36 minutes ago, BTM520 said:

I can't believe this thread is even up on this site...drive the car and drive it hard (once warmed up of course), enjoy the noise and have a smile on your face whilst making the car noisy and eating corners. 

Totally agree, if you are concerned with your mpg, you've bought the wrong car! 

27 mpg on my commute, less when spanking her, even less in town. I haven't monitored mpg since the first couple of months of ownership, my computer doesn't move off remaining mileage. 

@Stuart21UK dedication to change your exhaust before popping to the local shops.

 

[PaulQ]

1 hour ago, BTM520 said:

I can't believe this thread is even up on this site...

If your car only did 10mpg you would want to know why. Everyone monitors mpg to some extent 

 

[Nobbie]

2 hours ago, BTM520 said:

I can't believe this thread is even up on this site...drive the car and drive it hard (once warmed up of course), enjoy the noise and have a smile on your face whilst making the car noisy and eating corners. 

Nobody's telling you how to drive your car, why do you feel the need to tell others how to drive theirs? Some people have these as daily drivers and MPG matters when you're doing 10k a year. Mine's a weekend toy, so MPG is just another stat really, but I do find it interesting what you get in different driving conditions.

Mine's a 2.5 tip and get's high teens in spirited driving. It was interesting (to me) when returning from Scotland with a failed steering pump down the M6 to look at the MPG. For the first bit following some other Boxster at 70-80 I was only getting about 26mpg, but after they turned off and I was in no rush I bimbled along at 60 and got about 34mpg. All according to the trip computer, but it seems fairly accurate based on comparing with mileage between brimming the tank.

I think the gearing on mine limits MPG at higher motorway speeds, but it's not something I do often.

 

[½cwt]

Don't monitor mine closely as it is largely use like @Nobbie to about 3.5k mile a year.  That said last summer at 70 ish on long UK Motorway runs I thought 36mpg ont eh OBC was pretty good.   Dropped to about 32 on French autoroutes at 80ish but in my normal use pattern about 28 which for a 252bhp n/a sports car in town and pushed along on back roads is quite acceptable, about the same as my Impreza's used to do when I was doing 20k miles a year in them, although at the 'Ring the Scooby dropped to an estimated 8 mpg!  so I must have been trying and I was getting fuel starvation at the end of the third lap each time!

 

[GmanB]

The only way to accurately measure mpg is to ignore the estimates the computer gives and measure the fuel that goes in from bone dry, run the tank dry again and record the mileage done (plus around 5-10% if you have stock wheels and tyres). Most cars post 2005 have economy readings on a computer and in my experience none of them are ever accurate. How can they be when the speedometer is always overstated?

[usman10316]

When I daily drove my boxster I averaged between 30-35 mostly. This was a 25 mile journey each way. Not much traffic and a lot of fun. Now it's more of a weekend car and I'm averaging around 25 as I have more fun in it than think about it's mpg. 

[Stuart21UK]

6 hours ago, GmanB said:

Totally agree, if you are concerned with your mpg, you've bought the wrong car! 

27 mpg on my commute, less when spanking her, even less in town. I haven't monitored mpg since the first couple of months of ownership, my computer doesn't move off remaining mileage. 

@Stuart21UK dedication to change your exhaust before popping and crackling to the local shops.

 

thanks...but edited for complete accuracy

[Stuart21UK]

5 hours ago, PaulQ said:

If your car only did 10mpg you would want to know why. Everyone monitors mpg to some extent 

 

only if you have time to take your eyes off the road

[GmanB]

1 minute ago, Stuart21UK said:

thanks...but edited for complete accuracy

Probably just a switch on a 981 as well..

[½cwt]

2 hours ago, GmanB said:

.... How can they be when the speedometer is always overstated?

If you delve into the codes that display various data outputs on the heater display on various cars (I've only tried it on a SEAT several years ago), the speed output, albeit in kph, is the correct not overstated figure, so the car does know its true speed there is just a factor added to the speedo display speed to ensure compliance with the -0 + 10% in the regulations.  Is an OBC fully accurate?  No, but it isn't affected by the speedo factor although I do find them to be slightly optimistic but that is also no doubt part of the ownership feelgood programme. 

As you say fill to brim and refill to brim (preferably from the same pump and at the same time of day or at least ambient temp so the mass not just volume is the same. BTW 5 to 6 am is the best time to refuel as the fuel is at is coldest and therefore densest if you are being really geeky on value for money.....) with a known mileage on the trip is the only way; unless you want to fit and calibrate a full rally trip computer for real accuracy on you mileage too.

[Patt]

My daily commute in the 981 normally reads 10mpg - it won't go lower like the 986.

Weekend drive outs usually get to 23-27.  Drives T'up norvf = 35+

[zadocbrown]

On 9/20/2019 at 12:10 PM, Hughsehhh said:

Just wondering what the 2.5 986 owners get approximately from a tank, I got 415 miles last night in perfect conditions (clear traffic, 180 mile journey, mainly motorway driving with some 50mph limits thrown in). But the on board computer said another 35 miles to go, albeit the fuel light had been on some time, so I didn't want to risk it. Now it's a 57l tank in the car and it was brimmed the last time I filled up, so the obc reckons i averaged 36.3 mpg. At one point I was over 38 until I blasted the last 20 miles or so. 

A few questions 

1. How accurate is the distance to empty calculator 

2. There are two lights that come on when the fuel is low, I've never gone past the first but can you?

3. Is this particularly high fuel economy a sign that I may be missing some performance somewhere, I.e. coil packs knackered?

I realise I'm refreshing an old thread here, but rather that than create a new

Don't know about the first two questions, but in my 2.7 I've seen the distance remaining go past 400 and around 34mpg on motorway (modest trip distance) so your reported stats don't strike me as abnormal.

[Nobbie]

On 9/21/2019 at 11:19 PM, ½cwt said:

If you delve into the codes that display various data outputs on the heater display on various cars (I've only tried it on a SEAT several years ago), the speed output, albeit in kph, is the correct not overstated figure, so the car does know its true speed there is just a factor added to the speedo display speed to ensure compliance with the -0 + 10% in the regulations.  Is an OBC fully accurate?  No, but it isn't affected by the speedo factor although I do find them to be slightly optimistic but that is also no doubt part of the ownership feelgood programme. 

As you say fill to brim and refill to brim (preferably from the same pump and at the same time of day or at least ambient temp so the mass not just volume is the same. BTW 5 to 6 am is the best time to refuel as the fuel is at is coldest and therefore densest if you are being really geeky on value for money.....) with a known mileage on the trip is the only way; unless you want to fit and calibrate a full rally trip computer for real accuracy on you mileage too.

Isn't the fuel stored in underground tanks? Can't see how the temperature in them is going to change more than a tiny fraction of a degree over the course of a day.

[½cwt]

14 minutes ago, Nobbie said:

Isn't the fuel stored in underground tanks? Can't see how the temperature in them is going to change more than a tiny fraction of a degree over the course of a day.

It won't change a lot, no, but also depends when it was delivered.  If the tanker has been traveling in 30°C direct sunlight it will take time to cool.  In F1 you are not allowed to cool fuel either before it goes into the car or whilst in the car.  Mercedes had a rap on the knuckles for this just last weekend.

Just highlighting other variables in fuel consumption calculations.

[PaulQ]

On 9/23/2019 at 11:11 AM, Patt said:

My daily commute in the 981 normally reads 10mpg - 

Sounds like your commute is even shorter then mine......

 

[Patt]

2 miles - if traffic is really bad it will rise to 17mpg while I'm stationary

[Paul chocks]

I've been a bit of a fuel nerd on my car and have checked the mpg on pretty much every fill over the past 40,000 miles!  I always fill and reset counter, so no computer nonsense.  Remarkably consistent, around 26-27 mpg on every tank full, regardless of how its been driven (I have never done a steady 60 for a full tank).  Nerdishness did pick up a failure of an O2 sensor.  Noticed the mpg suddenly dropped to 18 a few years back, took it to a specialist who swapped out sensor and back to 26 again.