[RobManser]

I own a 2016 530d M Sport, bought from a BMW dealer at 50,000 miles last December. Back then it got just over 60mpg if I was careful on a long journey, 50-55 if I wasn't careful. In mixed local driving, I got 50 and 45mpg respectively. A year later I'm at 59k miles and all these figures have dropped by about 10mpg. On Boxing Day I drove 80 miles non stop on the motorway with the cruise set at 65mph and it recorded 49mpg - in the past it would have been over 60mpg without an issue if I did that. The other problem is it's started sticking and then jerking free when pulling away from rest.

The changes are obviously that the car's a year and 9,000 miles older, but also that I now work from home, so instead of doing two 37 mile trips per day commuting I'm doing two 7 mile trips a day. I do occasionally go further and stress the car more: I tow a heavy trailer on 1-2 hour trips, go to the coast windsurfing with the roof loaded up (again, 1-2 hours), and do some long trips (Cornwall this summer for example), but these are once a month occurrences now, not regular things. Have my short trips affected the engine and/or drivetrain? Can it be rectified? I tried a bottle of Forte, but that didn't really help. Once the car's fully warm on a longer trip I use full throttle and revs when I can, so it doesn't just chug about.

Thanks in advance.

[RobManser]

Any ideas before I take it to BMW and empty my wallet?

[Sylverlee]

same thing happens to me. Lost about 10-15% mpg from 30k miles 535i to 65k miles.

[Global-F10]

Have you kept up with scheduled maintenance? Air filter for example?

Unscheduled maintenance like tires, tire pressure and alignment could affect your MPGs although slightly

[Sylverlee]

I have. Although haven't done walnut blasting. I've also had some mods done after. XHP transmission tune, MHD.

[HighlandPete]

Originally Posted by RobManser

Any ideas before I take it to BMW and empty my wallet?

I'd be checking engine coolant temperature, (ECT), as a first simple check. Check out warm up time and where ECT settles for constant running. Low ECT will mean more fuel is burned.

EGR system could also be an issue. If the EGR valve is sticking, flow rates can affect mpg.

Carbon build up in the inlet manifold/porting is another possibility, with more short trips and running colder.

[RobManser]

Originally Posted by Global-F10

Have you kept up with scheduled maintenance? Air filter for example?

Unscheduled maintenance like tires, tire pressure and alignment could affect your MPGs although slightly

Thank you. I've had every service done on time by BMW, and it's recently been to them for a service. I think I can sense a minor alignment issue though on turn-in to corners, so that's next on my list, but I thought I'd wait for new tyres first.

[RobManser]

Originally Posted by HighlandPete

I'd be checking engine coolant temperature, (ECT), as a first simple check. Check out warm up time and where ECT settles for constant running. Low ECT will mean more fuel is burned.

EGR system could also be an issue. If the EGR valve is sticking, flow rates can affect mpg.

Carbon build up in the inlet manifold/porting is another possibility, with more short trips and running colder.

Thanks. EGR sounds like a possibility. Would that show up when the dealer plugged into the car? It's just been for a service.

[TEF]

Your M5 diesel is likely to have the higher output I6 diesel relative to a 535d here in the US. Despite that, your initial mpg figure of 60 mpg is much higher than what I've achieved in the US. My 2016, bought new, gets around 46 mpg at 70 mph and around 50 mpg at 55 mph. Suburban driving yields about 38 mpg. Therefore, even your lower mpg figures exceed my best numbers. Just curious, does the UK still dispense fuel in "imperial gallons"? Here in US one gallon is 3.78541 liters. Is the same true for a gallon of fuel in the Berkshire?

Just a thought, your shorter commutes of only 7 miles each way may be the reason for lower mpg number. Generally, diesels perform best a their designated operating temperature. Relative to your 37-mile commutes, your car is now spending a larger percentage of the journey at colder temperatures, so hence poorer mpg. BMW tries to offset this by installing shutters in space between grill openings and radiator, so if theses are not operating as they should (i.e. stuck open), that too could affect your mpg figures.

[RobManser]

Originally Posted by TEF

Your M5 diesel is likely to have the higher output I6 diesel relative to a 535d here in the US. Despite that, your initial mpg figure of 60 mpg is much higher than what I've achieved in the US. My 2016, bought new, gets around 46 mpg at 70 mph and around 50 mpg at 55 mph. Suburban driving yields about 38 mpg. Therefore, even your lower mpg figures exceed my best numbers. Just curious, does the UK still dispense fuel in "imperial gallons"? Here in US one gallon is 3.78541 liters. Is the same true for a gallon of fuel in the Berkshire?

Just a thought, your shorter commutes of only 7 miles each way may be the reason for lower mpg number. Generally, diesels perform best a their designated operating temperature. Relative to your 37-mile commutes, your car is now spending a larger percentage of the journey at colder temperatures, so hence poorer mpg. BMW tries to offset this by installing shutters in space between grill openings and radiator, so if theses are not operating as they should (i.e. stuck open), that too could affect your mpg figures.

Thanks for your thoughts.

M Sport just refers to the suspension (and I think the gearbox?) - it's a standard '30d engine. No relation to the M5.

Yes, the mpg is of course terrible on my 7 mile trips to nursery and back with my son, as a good proportion of it is with a cold engine. The change is permanent though - I'm getting bad mpg on all trips, including long trips across the country.

[Blue Angel]

The 530d is mechanically the same car as the North American 535d with a few minor differences as far as I can tell; the lack of active grille shutters being one (my NA 2016 535d does not have active shutters).

On a recent trip averaging 90-100 km-h (55-60 MPH) I got 5.3 L/100km (44 US MPG, 53 Imp MPG). This is an XDrive car with new snow tires and temps below freezing, so this could be slightly higher in better conditions, but not by a lot, and is slightly down on what a rwd car would get.

I'm pretty sure this is normal for my car, though I did buy it with 88k kms on it.

The only thing that comes to mind is regen of the dpf. Perhaps your short trips are requiring the car to do a dpf regen whenever you get on the highway and up to temperature? If you have the BimmerLink app and an OBD BT dongle you can check the regen status. I would expect lower mileage on any drive where a regen takes place.

[Blue Angel]

"…it's started sticking and then jerking free when pulling away from rest."

This could be a sticking brake caliper, though if it was causing such a drastic mileage reduction you would probably notice it getting extremely hot and smelling burnt. To check this, go for a short drive where you don't use the brakes much, then stop and check if one brake is any hotter than the rest. You should be able to tell by putting your hand near the rotor and feeling for radiating heat (I wouldn't touch the actual brake disc as it could be very hot). Use an infrared temperature gun if you have one.

If you use the Auto Hold feature the brakes stay applied until you touch the accelerator, which could lead to that sticking feeling? Just putting that out there in case it's engaged by accident or something.

[RobManser]

Originally Posted by Blue Angel

"…it's started sticking and then jerking free when pulling away from rest."

This could be a sticking brake caliper, though if it was causing such a drastic mileage reduction you would probably notice it getting extremely hot and smelling burnt. To check this, go for a short drive where you don't use the brakes much, then stop and check if one brake is any hotter than the rest. You should be able to tell by putting your hand near the rotor and feeling for radiating heat (I wouldn't touch the actual brake disc as it could be very hot). Use an infrared temperature gun if you have one.

If you use the Auto Hold feature the brakes stay applied until you touch the accelerator, which could lead to that sticking feeling? Just putting that out there in case it's engaged by accident or something.

Thanks, I'll try that. I doubt it, because when the car comes to rest I'd expect it to stop quicker than expected, but it's worth a look and is something I hadn't thought of.

The Auto Hold feature sounds great until you realise it keeps your brake lights lit up, annoying the person behind you! I just use Park now do I don't piss people off.