Shocking fuel efficiency

Suedezed

Suedezed

Newbie
British Zeds
Joined
May 15, 2023
Points
3
Location
Wirral
Model of Z
2.0
What’s everyone’s mpg? I feel like I’m always topping up. Using on board computer I clocked in 78 miles for half a tank. Is that about right? 2l 5 speed manual, 2000. Thanks.
 
What's the mpg showing on the on-board computer?
 
Calculate what your MPG by filling the tank and zero the trip meter. Drive the car as you normally do and when nearly empty record the miles on the trip meter and fill the tank again. Record the amount it takes to fill the tank. Then it's simple maths to calculate what you're actually getting.

Trip meter reading divided by number of litres to fill the tank. Then multiply by 4.5 for actual MPG.

Compare that to your OBC reading.
 
Suedezed said:
I might be being a bit stupid here, I can’t see any mpg figure!
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Have you actually GOT an on-board computer? What does your clock look like? Is it like a "clock", or is it a digital display? If it's digital, press your indicator stalk IN, and you'll see the different functions (including mpg).
 
Can't be right surely. Our 1998, Z3 2.8L with after market exhaust. 400 miles to tank. AVG 30 mpg. Not dithering around either.
 
400 miles? best I've had is around 330 from my 2.8. My OCD makes me record every fill up and the mileage. I just checked my log and the most I've ever put in is 45ltrs and on that occasion I'd covered 313 miles giving me 31.6 MPG. The Z3 tank is 51ltrs if my memory serves me right.
 
Last edited:
My 2.0 averages 27mpg according to the computer, around town and occasional country blast😁
 
Rod and Kate said:
Can't be right surely. Our 1998, Z3 2.8L with after market exhaust. 400 miles to tank. AVG 30 mpg. Not dithering around either.
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400 miles to the tank :oops:
 
Devon Z said:
My 2.0 averages 27mpg according to the computer, around town and occasional country blast😁
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My 3.0 averages 28.5 in similar driving (according to the computer), so it's interesting that all Z3s must be similar mpg, regardless of engine size.

Saying that. my 2.0 E89 Z4 (which is faster than the 3 litre Z3), gets 35-36.
 
My 2.2’s average tank to tank consumption is 26mpg…and about 250ml of oil every second tank.
 
180- 220 miles per tank - urban, b road.
70-80 on a full tank on track
2.8 manual.
Best I got was about 250 but that was because my right ankle was injured =))

Even by my standards your 78 on the first half the tank sounds heavy - the first ‘half’ is more like 3/4 as it the second half drops faster.

To rule out a dodgy gauge you need to record the miles in between fills.

Ie brim tank, drive, when you brin tabk again record the miles vs litres filled to brim it again and you’ll have the actual mpg.
 
My 1999 2.8 averages about 28 with mixed driving. Up to 34 on the motorway.
I would put a code reader on it. Sometimes codes are thrown up that don't trigger the dashboard light at first.
 
I would be plugging in diagnostics and looking at live data fuel trims, if they are high then you probably have an air leak thats being picked up in the exhaust and fooling the car into thinking its running lean, it then demands more fuel at the injectors to richen it up. This will go on until its adding up to 20% more fuel until it gives up trying to correct it and sets the EML as an attention getter. If you cant find any air leaks visually a smoke test probably will first go.
 
I’m getting high 20’s to low 30’s in a 3.0l manual.
Even got an average of 34 on the lakes drive- out 😮
 
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