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Chris28

Poor MPG 540i

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I’m struggling to get my MPG on my 2001 540i above 15 - 17 mpg. Obviously I didn’t by a 4.4 V8 for economy but I’m confident I should be getting 20 - 25mpg. I don’t drive the car hard and when it’s on long carriage way and motorway journeys the highest I can get it to is 17mpg. And that’s trying to drive economically!

I’ve changed the MAF sensor which didn’t help. I’ve only had the car a few months. The car is a Japanese import and its recently been fully serviced. It’s showing no faults.

I’ve read the Japanese cars came with a different ratio diff, but it sits happily at 3k RPM at 70mph so I don’t think this is the reason.

What would be the first thing I should look to change or check? Fuel filter? Maybe possible vacuum leaks? New coil packs?

 

Any suggestions would be great. Thanks.

 

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Was it an OEM MAF or aftermarket? Might be worth getting the codes read, just in case. Re MAF / sesnsors, usually OEM BMW is recommended for engine sensors FYI

 

Thinking the lambda sensors may need looking at/changing and making sure there is no extra air being sucked in either (although rough running would have reared it’s ugly head by now if it were this)

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12 minutes ago, d_a_n1979 said:

Was it an OEM MAF or aftermarket? Might be worth getting the codes read, just in case. Re MAF / sesnsors, usually OEM BMW is recommended for engine sensors FYI

 

Thinking the lambda sensors may need looking at/changing and making sure there is no extra air being sucked in either (although rough running would have reared it’s ugly head by now if it were this)

 

Theres no idle problems. And the MAF is a good quality Bosch one.

Would the lambda sensors be a cheap job? I’d be willing to swap them out to see if it helps, if it’s too not expensive.

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2 hours ago, pidgeonpost said:

I'm not at all familiar with this model, but is 3k rpm at 70mph normal? Our E60 only registers around 1600-1700 rpm at that speed. 

I imagine your E60 is a diesel? 

3k @70 sounds fine for a petrol engine, esp with a Japanese Market final drive. 

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8 minutes ago, duncan-uk said:

Daft question is this calculated mpg or on the obc? If the latter might it be set to US gallons?

 

I hope not! 16 US gallon is only 13 imperial gallon. 

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I’m going to do a vacuum test tonight. I watched a couple of videos online of people squirting brake cleaner at all the intake pipes and gaskets. If the idle changes when you squirt an area then there’s a leak there. Sounds a hill-billy but I’ll give it a go.

 

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21 minutes ago, duncan-uk said:

Daft question is this calculated mpg or on the obc? If the latter might it be set to US gallons?

 

Actually I've totally worked that out wrong. I googled it there. 1 US gallon is 0.83 imperial. So 16 MPG would be 18.72? I think I worked that out right? Either way, it’s not great.

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1 hour ago, jonbill said:

I imagine your E60 is a diesel? 

3k @70 sounds fine for a petrol engine, esp with a Japanese Market final drive. 

 

I just double checked it on the way to work. It’s 2500 rpm at 70mph.

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36 minutes ago, grapefruit said:

Have you checked the thermostats - via the hidden menu - to make sure it's getting up to temperature?

 

I’m not too sure about this one. What’s the secret menu?

i did swap the thermostat a few weeks ago though because it was showing a fault with it. It had a rough idle back then and the new thermostat fixed it.

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4 hours ago, pidgeonpost said:

I'm not at all familiar with this model, but is 3k rpm at 70mph normal? Our E60 only registers around 1600-1700 rpm at that speed. 

 

That's diesel though; petrols rev higher

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You should be doing better than that. On a steady run at 70/85 mph my Jap 540 will achieve around 30mpg. Not relied on the computer figues, but have done full to full calculations as well. 

 

Local running about, short journeys, 18 to 24 mpg.

Edited by Loadmaster

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2 hours ago, Chris28 said:

 

I just double checked it on the way to work. It’s 2500 rpm at 70mph.

 

1 hour ago, d_a_n1979 said:

 

That's diesel though; petrols rev higher

True. I'm sure I've made that mistake before.  :rolleyes:

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26 minutes ago, pidgeonpost said:

 

True. I'm sure I've made that mistake before.  :rolleyes:

 

Haha I'm still not used to it; moving from a 530i to a 730D; it just feels under-revved :lol: 

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3 hours ago, Loadmaster said:

You should be doing better than that. On a steady run at 70/85 mph my Jap 540 will achieve around 30mpg. Not relied on the computer figues, but have done full to full calculations as well. 

 

Local running about, short journeys, 18 to 24 mpg.

 

Cool, so theres room for improvement then. Thanks for letting me know what your getting.

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6 hours ago, Loadmaster said:

You should be doing better than that. On a steady run at 70/85 mph my Jap 540 will achieve around 30mpg. Not relied on the computer figues, but have done full to full calculations as well. 

 

Local running about, short journeys, 18 to 24 mpg.

 

Agreed. Similar figures to what I'm getting in my 540i

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 My 540 will do around 16-18mpg around town, 25-28mpg mixed driving and 30mpg on a steady run. A 70mph cruise will see the revs at just under 2k. OP, are you calculating the mpg yourself or relying on the trip computer, if the latter are you resetting it everytime you fill up?

 

22 hours ago, Chris28 said:

 

Theres no idle problems. And the MAF is a good quality Bosch one.

Would the lambda sensors be a cheap job? I’d be willing to swap them out to see if it helps, if it’s too not expensive.

 

 Lambdas aren't that expensive (about £50 for Bosch ones if I recall correctly) but it's  money wasted if it doesn't cure the fault, do you have INPA software? You can look at the live data on there which will tell you if your lambdas are working correctly, other than that, I would echo the advice on checking it's getting up to temperature, if it's running cold it'll drink fuel. 

 

Edit, INPA will show you exactly how hot/cool the engine is running too and very nice motor by the way! :)

Edited by NWJW

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22 minutes ago, NWJW said:

 

 My 540 will do around 16-18mpg around town, 25-28mpg mixed driving and 30mpg on a steady run. A 70mph cruise will see the revs at just under 2k. OP, are you calculating the mpg yourself or relying on the trip computer, if the latter are you resetting it everytime you fill up?

 

 

 Lambdas aren't that expensive (about £50 for Bosch ones if I recall correctly) but it's  money wasted if it doesn't cure the fault, do you have INPA software? You can look at the live data on there which will tell you if your lambdas are working correctly, other than that, I would echo the advice on checking it's getting up to temperature, if it's running cold it'll drink fuel. 

 

Edit, INPA will show you exactly how hot/cool the engine is running too and very nice motor by the way! :)

 

+1 

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3 hours ago, NWJW said:

 

 My 540 will do around 16-18mpg around town, 25-28mpg mixed driving and 30mpg on a steady run. A 70mph cruise will see the revs at just under 2k. OP, are you calculating the mpg yourself or relying on the trip computer, if the latter are you resetting it everytime you fill up?

 

 

 Lambdas aren't that expensive (about £50 for Bosch ones if I recall correctly) but it's  money wasted if it doesn't cure the fault, do you have INPA software? You can look at the live data on there which will tell you if your lambdas are working correctly, other than that, I would echo the advice on checking it's getting up to temperature, if it's running cold it'll drink fuel. 

 

Edit, INPA will show you exactly how hot/cool the engine is running too and very nice motor by the way! :)

 

I’ve been using the trip computer for the MPG. I rarely let the tank go to empty so I haven’t had the chance to check it the old fashioned way. Are the trip computers prone to being inaccurate? 

The thermostat is brand new so I’d like to think the cars getting up to temp but who knows.

I do have INPA software though I’m new to it all. Can you point me into the right direction to check it’s getting up to temp? 

Thanks.

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