23i fuel consumption

R

romainh

Member
Hi,

I bought a Z4 23i only 2 months ago and while I haven't driven it lots - about 500mi - the fuel consumption is slightly higher than I expected, around 25-26mpg. I do about 50% city driving and the other 50% weekend trips in Surrey, mostly on 40-50mph roads, rarely accelerating strongly.

When I bought it, the odometer indicated 34.4mpg average over about 50k miles. While it must have been mostly driven on motorways, I still expected the fuel consumption to land around 30mpg, even with a mix of city and road driving. I first filled up a tank with E10 as it was all I could find, and since did a premium fuel refill.

The car is stored outside at night which I know impacts fuel consumption at the start, especially when it's cold. However it's running on the smaller 17' wheels, with tyres well inflated and the oil level is kept in check on the dashboard.

Am I missing something which could be causing a higher fuel consumption, or do I simply have wrong expectations? Not a biggie but I would be curious to get your average MPGs and your conditions/styles of driving with the same engine

Please feel free to point me to a similar thread if there's already one. Thanks!
 
I think you have the wrong expectations, winter weather can drop mpg by 10% easily and city use will drop it even more - stop/start driving means the car hardly spends any time cruising in top gear which is where it needs to be for good economy.
Rob
 
Only other thing I can think of is to check your wheels after a run to see how hot they are. A binding brake could affect fuel consumption.
Don't think wheel size should make any difference as the combination of wheel and tyre size should keep the rolling circumference roughly the same.
 
I had a 30i manual, also on 17 inch wheels and kept outside overnight. I lived in Zone 1 London at the time so as you can imagine there was minimum 30 minutes of stop start driving on any drive, but I struggled to get less than 30mpg, even in winter. Average mpg for the 9 months I had it was about 31.

Obviously there are many variables, but your mpg does sound very low - unless you've yet to go above 2nd gear! :driving:

Have you verified your trip computer readout with your own calculation?
 
Always a good idea to check your air filter but to be honest I would just enjoy the car.
The 23i was my introduction to the Zed and while it might not be the fastest it is certainly the most fun with a great exhaust note in my opinion.
I would drive mine across the truly twisty roads of dartmoor, revs up, sport mode for more valve lift and usually in 3rd gear, the car sings when its set up like that and drives beautifully. I miss that car to be honest.....
 
I also drive a 23i
Mainly along country roads to work, rarely on the motorway but I’m getting a higher mpg than you.
I would’ve thought 30 isn’t an unreasonable expectation
 
32 mpg here over 14 months of ownership. Mostly 70 - 80 mph motorway. Plenty of short urban trips however. Yours feels a bit low I would agree
 
mcbutler said:
Always a good idea to check your air filter but to be honest I would just enjoy the car.
The 23i was my introduction to the Zed and while it might not be the fastest it is certainly the most fun with a great exhaust note in my opinion.
I would drive mine across the truly twisty roads of dartmoor, revs up, sport mode for more valve lift and usually in 3rd gear, the car sings when its set up like that and drives beautifully. I miss that car to be honest.....
Click to expand...

The extra valve lift only changes the throttle response (due to the lack of a throttle body) it doesn’t actually increase the power output :thumbsup:
Rob
 
Smartbear said:
mcbutler said:
Always a good idea to check your air filter but to be honest I would just enjoy the car.
The 23i was my introduction to the Zed and while it might not be the fastest it is certainly the most fun with a great exhaust note in my opinion.
I would drive mine across the truly twisty roads of dartmoor, revs up, sport mode for more valve lift and usually in 3rd gear, the car sings when its set up like that and drives beautifully. I miss that car to be honest.....
Click to expand...

The extra valve lift only changes the throttle response (due to the lack of a throttle body) it doesn’t actually increase the power output :thumbsup:
Rob
Click to expand...
I know I didnt state that it increases power, just valve lift - a very good video on YT about the N52 valve gear shows exactly how it works.
Although if you consider they used to fit 'high lift cams' to increase power in the old days I wonder why the dramatic increase in valve lift that the N52 gets makes no difference....... odd dont you think....
 
mcbutler said:
Smartbear said:
mcbutler said:
Always a good idea to check your air filter but to be honest I would just enjoy the car.
The 23i was my introduction to the Zed and while it might not be the fastest it is certainly the most fun with a great exhaust note in my opinion.
I would drive mine across the truly twisty roads of dartmoor, revs up, sport mode for more valve lift and usually in 3rd gear, the car sings when its set up like that and drives beautifully. I miss that car to be honest.....
Click to expand...

The extra valve lift only changes the throttle response (due to the lack of a throttle body) it doesn’t actually increase the power output :thumbsup:
Rob
Click to expand...
I know I didnt state that it increases power, just valve lift - a very good video on YT about the N52 valve gear shows exactly how it works.
Although if you consider they used to fit 'high lift cams' to increase power in the old days I wonder why the dramatic increase in valve lift that the N52 gets makes no difference....... odd dont you think....
Click to expand...

It’s because it doesn’t increase max valve lift, only a small amount of extra lift at the very bottom end of the scale to alter the throttle mapping.
The n52 gets some of its good economy from this method as it’s far more efficient than using a throttle butterfly to regulate the air flow.
Rob
 
My 7 mile daily journey to work, 3 urban 4 country, so barely up to temp. my 23i can achieve anything from 28 to 38 depending how it's driven and time of year.
If significant amount of motorway can get 44-48 mpg.

If shuffling along in urban traffic, i bet it would drop to 24. They are Autobahn cars.
I never baby the engine, at least every journey i push it to redline, which gives just under 60mph in 2nd.

Also see if putting key in, ignition on, wait several seconds, then ignition off.
Then start, tell me if that makes a difference. Does on my car, acceleration seems more rapid and lively, might improve mpg.

Also run through a tankful of Vpower super unleaded. (makes exhaust pop more).
 
Thanks all for your comments. Sounds like mine's a bit low-ish compared to what it should be. This is only based on computer readout though, so as suggested I'll do my own calculations at the next refill.

That's good to know about the air filter and binding brake, maybe something I can get checked by a local garage as maintenance isn't due until next March. I doubt it's either though as it's been well-maintained so far.

Now, I forgot to mention the gearbox - it's an automatic. I'm assuming this has a big influence on the MPG vs a manual? Still, if the few previous owners managed to get 34.4mpg overall then I should be able to get at least 30mpg..

I'm also planning on getting a cruise control retrofitted which should help improve fuel economy on longer drives.

And thanks for the suggestion flybobbie, I'll give that a go when I next go for a drive!
 
Mixture of motorway and urban driving (60 / 40) I am getting an average of 35.4 over the 4K miles I have driven since I bought the car.

Will see 40+ on a motorway but 30 locally and it will drop quite quickly after a motorway stint.

Still think thats pretty impressive as SWMBO only get 37 to 38 our of her 1.2 3cylinder DS
 
That does seem a bit low for anything with an N52 engine, but maybe it's a lot of shortish journeys so the engine isn't up to temperature much of the time?

I've had two E86s, a 325i and a 330i all with the N52 and they have all averaged between 31 and 34 mpg in the time I've had them (a total of 37K miles) but that is by my own measurement rather than the OBC.

And to be fair 90% of the miles were on motorways and A Roads for round trips of 50 or more miles outside of rush hours, although I have given all of them some welly once warmed up!

Although my current 330i is the lowest of them all at 31mpg because I had it during lockdown, so did loads more short trips last year.
 
Mr Tidy said:
That does seem a bit low for anything with an N52 engine, but maybe it's a lot of shortish journeys so the engine isn't up to temperature much of the time?

I've had two E86s, a 325i and a 330i all with the N52 and they have all averaged between 31 and 34 mpg in the time I've had them (a total of 37K miles) but that is by my own measurement rather than the OBC.

And to be fair 90% of the miles were on motorways and A Roads for round trips of 50 or more miles outside of rush hours, although I have given all of them some welly once warmed up!

Although my current 330i is the lowest of them all at 31mpg because I had it during lockdown, so did loads more short trips last year.
Click to expand...

Yes, there have been a few short journeys where the engine didn't quite get to temperature. Overall, it must be a combo of short city rides, automatic gearbox, first tank with E10 and recent cold temperatures. I also recently reinflated the tyres which I'm sure will help.

Thanks all for sharing your MPGs, and the few things to try if it doesn't improve. I'll keep monitoring and will report back :)
 
To be fair even high 20s is pretty good for any 6 cylinder petrol - I never got close to 30mpg with any of my previous 6s, but then they were older cars.

But I don't get too hung up on fuel consumption especially since I bought the M - I'd rather just enjoy the car! :D
 
I have a 23 Manual I drive around Surrey too - I get around 25-30 or at best 35 on a run according to the dodad in the dash but I do drive it hard once it's warmed up. You know I never thought about fuel economy until now, I much prefer the noise of redlining it through the Hindhead tunnel to an extra few MPG.
 
joolsburger said:
I have a 23 Manual I drive around Surrey too - I get around 25-30 or at best 35 on a run according to the dodad in the dash but I do drive it hard once it's warmed up. You know I never thought about fuel economy until now, I much prefer the noise of redlining it through the Hindhead tunnel to an extra few MPG.
Click to expand...

Fair enough, I haven't driven it through the Hindhead tunnel yet but I'll give it a go when I'm next down on the IOW! I have now driven it over slightly longer runs though and got around 40 mpg. In fairness, I had done a lot of inner city driving so all things considered 25-26 mpg was still decent considering BMW quote 24 mpg in these conditions.

Based on previous recommendations, I have checked the air filter which looks brand new (despite being 2 years old) and I doubt there's a binding brake as this would have come up on the MOT when I bought it.

Out of curiosity, what premium fuel do you put in? I haven't tried Vpower super unleaded as suggested above but a recent run on BP Ultimate seems to have done it some good
 
Good to know it does much better on longer runs, so it looks like your average is more to do with how you use the car than any issue with it.

As for fuel BMW recommend 98 RON whenever possible and AFAIK the only ones meeting that are Esso Synergy Supreme and Tesco Momentum which are 99 RON. The rest like Shell V-Power are 97 RON.

My nearest filling station is a Tesco so I tend to use their Momentum whenever possible, and they only charge an extra 7p a litre for it - all the brands like Esso, Sheel, BP, etc. tend to charge much more of a premium for their Superplus fuel.
 
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