[ReaperXI]

I own a 2017 M240i. I am getting around 20mpg (sometimes even much less) when I'm doing town driving as well as some slightly faster roads. I am in no way "thrashing" it but I've seen other owners of F-series M240i's averaging 30mpg while still having spirited drives. When I am stuck in traffic or driving round towns slow I even make it a point to switch it to Eco Pro mode, but it doesn't seem to improve the MPG figures I'm getting. Any idea why this is happening or how I can fix it? Hope someone can help!


Thanks

 

[OneTwenty]

This time of year is bad for fuel and MPG.

In the 6 years I've owned mine I've averaged around 26-27mpg over the year with mixed driving.

As a general rule these are the figures I get, depending how I drive and what mood I'm in:

Around town: 18-22mpg
Slightly further on A roads: 27mpg.
Further still with mixed A roads and DC/Motorway: 33mpg
Long run, mostly motorway with a few blasts at full throttle: 40-44mpg.

Winter is especially hard on the MPG but overall I think they are good on fuel for what they are. Never have an intake fitted though, as my annual MPG dropped from around 29mpg once I did that as the noise is so nice.

You could check your tyre pressures as if lower they will give worse mpg.

 

[padders]

Yep, I find the same. Around town in cold weather it can struggle to better 20mpg. On longer, faster runs it can do as much as 40mpg so unless you have a decent component of the latter you will typically return somewhere in the 20s for urban commuting.

Try a tank of Momentum 99 petrol. It costs about 4-5p more a litre than std 95 but anecdotally at least can add a mpg or two so may in fact be worth it. Oh and turning off your AC for part of journeys can help also, but leaving it off all winter is not recommended. If you are already using Eco-Pro you will notice that the car can steam up occasionally since limiting ac use is one of the strategies that mode uses.

Again I agree that tyre pressures may need to be higher when it is very cold out as the tyres don't come up to the same working temps as in summer so will be running at lower pressure and have greater drag. Try adding maybe 2psi as that would be the equivalent pressure change that 15ºC would make.

 

[muon]

Whats your average speed? Anything below 15mph I would say 20mpg is about right.

 

[ReaperXI]

This time of year is bad for fuel and MPG.

In the 6 years I've owned mine I've averaged around 26-27mpg over the year with mixed driving.

As a general rule these are the figures I get, depending how I drive and what mood I'm in:

Around town: 18-22mpg
Slightly further on A roads: 27mpg.
Further still with mixed A roads and DC/Motorway: 33mpg
Long run, mostly motorway with a few blasts at full throttle: 40-44mpg.

Winter is especially hard on the MPG but overall I think they are good on fuel for what they are. Never have an intake fitted though, as my annual MPG dropped from around 29mpg once I did that as the noise is so nice.

You could check your tyre pressures as if lower they will give worse mpg.

That's the thing, I haven't seen above 23 mpg. Admittedly, a lot of it is within a town with traffic - but still shocked as so many reviewers and owners report 30mpg average. That's also why everyone raves about the B58 - great performance, robust, and good economy for the performance. I haven't done a motorway run yet, so might need to test that.

Why do you say winter is especially hard on the MPG? I don't have an intake, luckily bought a used one that was totally stock! Tyre pressures are what they should be, even had a BMW technician confirm they should be 32psi all round according to the sticker on the door frame. Thanks for your reply though!

 

[ReaperXI]

Yep, I find the same. Around town in cold weather it can struggle to better 20mpg. On longer, faster runs it can do as much as 40mpg so unless you have a decent component of the latter you will typically return somewhere in the 20s for urban commuting.

Try a tank of Momentum 99 petrol. It costs about 4-5p more a litre than std 95 but anecdotally at least can add a mpg or two so may in fact be worth it. Oh and turning off your AC for part of journeys can help also, but leaving it off all winter is not recommended. If you are already using Eco-Pro you will notice that the car can steam up occasionally since limiting ac use is one of the strategies that mode uses.

Again I agree that tyre pressures may need to be higher when it is very cold out as the tyres don't come up to the same working temps as in summer so will be running at lower pressure and have greater drag. Try adding maybe 2psi as that would be the equivalent pressure change that 15ºC would make.

That's the thing, I haven't seen above 23 mpg. Admittedly, a lot of it is within a town with traffic - but still shocked as so many reviewers and owners report 30mpg average. That's also why everyone raves about the B58 - great performance, robust, and good economy for the performance. I haven't done a motorway run yet, so might need to test that.

I spoke to a friend at BMW who also suggested premium fuel - will give that a go next time I refill. I have my AC/heating on regularly in the winter - but that isn't something I can do without in the cold! I changed that setting within the iDrive menu for Eco Pro to not restrict ventilation functions.

My friend at BMW also recommended 32psi all round, hence why I stuck with those pressures as they're from the manufacturer!

 

[padders]

That's the thing, I haven't seen above 23 mpg. Admittedly, a lot of it is within a town with traffic - but still shocked as so many reviewers and owners report 30mpg average. That's also why everyone raves about the B58 - great performance, robust, and good economy for the performance. I haven't done a motorway run yet, so might need to test that.

I spoke to a friend at BMW who also suggested premium fuel - will give that a go next time I refill. I have my AC/heating on regularly in the winter - but that isn't something I can do without in the cold! I changed that setting within the iDrive menu for Eco Pro to not restrict ventilation functions.

My friend at BMW also recommended 32psi all round, hence why I stuck with those pressures as they're from the manufacturer!

23mpg is indeed low, but I can see that happening if I drove in the middle of London or any other big city with no faster unimpeded mileage. My commute ranges from 23mpg to 27mpg heading in and out of Birmingham which has less snarl ups that London in the main. As a comparison, on the same journey my 911 rarely exceeds 20mpg, so my B58 car is my economy choice! It will get better when it gets warmer, I gain 2-3mpg in summer.

Oh the heating uses no extra fuel at all, that is just waste engine heat, it is running the AC compressor that represents a small parasitic loss. You can have all the heat you want, but unless you actually need the ac on, to demist or cool down quickly for instance, you can get a slight mpg saving with the compressor off. Eco-Pro will only do this, cycle the compressor on and off, not throttle back the heat level. You can do it yourself with the button if you don't want the other Eco-Pro downsides but don't expect miracles.

 

[ReaperXI]

23mpg is indeed low, but I can see that happening if I drove in the middle of London or any other big city with no faster unimpeded mileage. My commute ranges from 23mpg to 27mpg heading in and out of Birmingham which has less snarl ups that London in the main. As a comparison, on the same journey my 911 rarely exceeds 20mpg, so my B58 car is my economy choice! It will get better when it gets warmer, I gain 2-3mpg in summer.

Oh the heating uses no extra fuel at all, that is just waste engine heat, it is running the AC compressor that represents a small parasitic loss. You can have all the heat you want, but unless you actually need the ac on, to demist or cool down quickly for instance, you can get a slight mpg saving with the compressor off. Eco-Pro will only do this, cycle the compressor on and off, not throttle back the heat level. You can do it yourself with the button if you don't want the other Eco-Pro downsides but don't expect miracles.

Right I see. Have you got an M240i as well or just another car with the same engine?

Got you on the heating/AC situation. If it's a tiny difference then that's fine, if it was significant then I might change it around a bit.

So in conclusion I shouldn't be worried? Just concerned as I mentioned that around town its saying im averaging 12-17mpg. It only increases when I go onto faster roads. I'll keep an eye on it through summer, how come mpg figures increase in the summer? Also I'll try other suggestions such as using premium fuel for the next time I refill.

At what point should I "be concerned" and maybe get BMW to have a look if there's anything wrong mechanically?

 

[padders]

My car is the coupe, the M240i. Look in my sig. this performs basically the same as yours as it is very similar.

I’d say you should be worried if you car doesn’t easily return mid 30s+ on any decent run above 40mph when you don’t have to stop start too much. A motorway run for instance. One other thing. If your journeys are very short, like 15mins or less then you may be suffering a bigger effect on mpg of the warm up phase. It takes that long to get the engine up to temp and it burns more fuel when cold.

 

[ReaperXI]

My car is the coupe, the M240i. Look in my sig. this performs basically the same as yours as it is very similar.

I’d say you should be worried if you car doesn’t easily return mid 30s+ on any decent run above 40mph when you don’t have to stop start too much. A motorway run for instance. One other thing. If your journeys are very short, like 15mins or less then you may be suffering a bigger effect on mpg of the warm up phase. It takes that long to get the engine up to temp and it burns more fuel when cold.

Right I see.

One of these days I'll do a roundtrip on a motorway and see what the mpg turns into (I assume test it in the comfort/sport mode rather than eco pro). SHould I reset the average MPG before going on this run or just leave it at what it was?

Journeys are relatively short, so that could be the issue. I always make it a point to let the engine warm up before moving off, letting the needle drop and for the cold start to finish but I also get that despite doing that, the engine isn't as warm as it would be if I did a 1 hour journey as opposed to a 15 minute one, even if I let the car warm up on start-up for the same duration.

 

[OneTwenty]

That's the thing, I haven't seen above 23 mpg. Admittedly, a lot of it is within a town with traffic - but still shocked as so many reviewers and owners report 30mpg average. That's also why everyone raves about the B58 - great performance, robust, and good economy for the performance. I haven't done a motorway run yet, so might need to test that.

Why do you say winter is especially hard on the MPG? I don't have an intake, luckily bought a used one that was totally stock! Tyre pressures are what they should be, even had a BMW technician confirm they should be 32psi all round according to the sticker on the door frame. Thanks for your reply though!

When the weather is much colder it takes a lot longer for the engine to warm up so uses more fuel. Also colder air does tend to increase fuel usage somewhat. All my cars have dipped in winter on fuel economy, especially my old 120d which would drop 10mpg in winter.

I don't use mine much during the week, but I do go in to town 2-3 times which is a 5 mile each way run on the main roads. If I drive carefully I can get 25mpg, but you only need a few jams and traffic stops and it drops down to 20mpg. If I give it some it can be as low as 17-18.

But if we go on a longer run and I just take it easy in Comfort, sticking to 60-70 and with maybe 6-7 full throttle blasts in a 50 mile round trip it normally does 28-30mpg quite easily. We go to York quite a bit which is around 90 miles each way, no motorway etc and I normally get around 33-35mpg on that run. That's 4 up and me overtaking whenever I get chance and enjoying the power every now and then, so I don't try to get good fuel.

Try going on a longer run and sticking to "normal" driving in Comfort with the odd overtake and see what you get. I never really use Eco Pro as it happens.

 

[OneTwenty]

I always make it a point to let the engine warm up before moving off, letting the needle drop and for the cold start to finish but I also get that despite doing that, the engine isn't as warm as it would be if I did a 1 hour journey as opposed to a 15 minute one, even if I let the car warm up on start-up for the same duration.

Just on that last point, that's about one of the worse things you can do for an engine, especially a B58. The owners manual even says drive off immediately and don't wait. Although I think you mean you just let the cold start finish, rather than actually waiting for the engine to be up to temp which would take 10-15 minutes!!

Either way, just drive off straight away once you start the car and don't give it full beans for a few miles.

One other question - is yours an auto or manual? The auto is much better on fuel allegedly.

 

[ReaperXI]

Just on that last point, that's about one of the worse things you can do for an engine, especially a B58. The owners manual even says drive off immediately and don't wait. Although I think you mean you just let the cold start finish, rather than actually waiting for the engine to be up to temp which would take 10-15 minutes!!

Either way, just drive off straight away once you start the car and don't give it full beans for a few miles.

One other question - is yours an auto or manual? The auto is much better on fuel allegedly.

Yeah I will try all the stuff you suggested in your last reply - thanks for all the suggestions!

Yes! I did mean I wait just until the cold start finished. I don't sit and wait for it to get to temperature first as if I did I wouldn't get anywhere on time 😂 And yes, I am cautious for the first few miles before really going for it with any car I drive, so I do the same with a performance car too.

It is indeed an auto - which was also one of the reasons I started this thread as I'm aware they're meant to be better on fuel than manuals, yet I'm still getting really low averages. Must just be a mix of time of year, town driving and things like that. Determined to get to the bottom of this and hopefully see some improvements. Any suggestions? Or at what point do I then consider taking it to BMW for a check to make sure there isn't any mechanical issues?

 

[OneTwenty]

I’d wait until it warms up. This was one of my trips tonight. Admittedly I was late due to a stupid wagon driver doing a 3 point turn on a main road, but it was 70% chilled driving.

 

[ReaperXI]

I’d wait until it warms up. This was one of my trips tonight. Admittedly I was late due to a stupid wagon driver doing a 3 point turn on a main road, but it was 70% chilled driving.

View attachment 20686

Thought you just said waiting til it warms up is bad for the B58 🤔

 

[padders]

Thought you just said waiting til it warms up is bad for the B58 🤔

I presume he was referring to the ambient temperature outside rather than the car.

I know you say you think your tyre pressures are ok, but check them on the drive first thing when there is frost on the ground like this morning and you might get a shock. Its easy enough, it is one of the options in Vehicle Status on the idrive . The 32psi shown on the door plate is for summer temps and is too low in winter since it will be more like 29psi at 0ºC and the tyres don't heat up as much at this time of year. The TPMS wheel sensors do typically under read by a psi or two but I bet you get a number in the high 20s rather than the 32 you might be expecting. Note the pressures they list for M+S tyres is a rather higher 35psi, despite the size being the same. I suspect this is to account for the pressure drop at lower temps rather than anything different about the tyre makeup.

 

[ReaperXI]

I presume he was referring to the ambient temperature outside rather than the car.

I know you say you think your tyre pressures are ok, but check them on the drive first thing when there is frost on the ground like this morning and you might get a shock. Its easy enough, it is one of the options in Vehicle Status on the idrive . The 32psi shown on the door plate is for summer temps and is too low in winter since it will be more like 29psi at 0ºC and the tyres don't heat up as much at this time of year. The TPMS wheel sensors do typically under read by a psi or two but I bet you get a number in the high 20s rather than the 32 you might be expecting. Note the pressures they list for M+S tyres is a rather higher 35psi, despite the size being the same. I suspect this is to account for the pressure drop at lower temps rather than anything different about the tyre makeup.

Ah right I see.
Yeah that makes sense about the tyre pressure. I’ll check it when I get in later. What PSI do you recommend for my tyres in the winter then? 35psi all round?

 

[padders]

Ah right I see.
Yeah that makes sense about the tyre pressure. I’ll check it when I get in later. What PSI do you recommend for my tyres in the winter then? 35psi all round?

It depends on when you are setting them really. On cold morning like today, I'd just make sure you have around 32psi in them. If you were setting the same tyres on a warmer day you'd need to put more in to allow for the drop on colder days. All the pressures on the door jamb are quoted at sea level and 20ºC, a temp not often seen at this time of year. In short, you need to change them for summer and winter really. This is why there was a fad of filling with Nitrogen, it's pressure doesn't change as much as air with temp.

 

[OneTwenty]

Thought you just said waiting til it warms up is bad for the B58 🤔

The weather!!

Mine is bad on fuel until around April time. In summer it's very good indeed.

 

[muon]

I’d wait until it warms up. This was one of my trips tonight. Admittedly I was late due to a stupid wagon driver doing a 3 point turn on a main road, but it was 70% chilled driving.

View attachment 20686

That is really bad for 25mph average.