I've owned the car for two years now, throughout which I have been collecting data on fuel economy, starting from the very day I purchased it. I use an Android app called aCar which I'd highly recommend.

With the current level of data collected, I think I can now make a well informed comment on what fuel consumption the E46 330d is capable of, and compare that against what BMW claimed it could do. All this bearing in mind the car is 11 years old and has just this week ticked over 150,000 miles.

BMW E46 330d Official MPG Fuel Economy


Let's start with the fuel consumption figures BMW claimed the E46 330d could achieve. The figures below have been taken straight from the owner's manual.
  • Urban - 30.7mpg (9.2)
  • Extra-urban - 53.3mpg (5.3)
  • Combined - 42.2mpg (6.7)

(Numbers in brackets are in litres/100km)

Before I delve into my data, it's important to understand some elements that will have affected the MPG.
  • The fuel used has always been standard diesel (not V Power or any other premium diesel)
  • Mileage range of fill ups: 123,000 - 150,000
  • Type of roads driven on (this is an estimate).
    • 2011
      • Urban - 50%
      • Extra-urban - 50%
    • 2012
      • Urban - 40%
      • Extra-urban - 60%
    • 2013
      • Urban - 40%
      • Extra-urban - 60%
  • Less than 1500 of the 27,000 miles driven has been on motorways.
  • The figures presented are actual, calculated MPG figures, NOT what the OBC (On Board Computer) reads.


BMW E46 330d Real World MPG Fuel Economy


The all important bit then, my results;

  • Minimum MPG recorded - 30.4
  • Maximum MPG recorded - 44.2
  • Average MPG overall - 37.3
    • Average MPG 2013 - 39.3
    • Average MPG 2012 - 37.1
    • Average MPG 2011 - 34.9

So what did the OBC say? Unfortunately for BMW it was very optimistic, for example, the maximum recorded MPG actually read 51.3mpg on the OBC. It seams that the higher the actual MPG is, the more inaccurate the OBC is.


Click to enlarge


Explaining The Numbers


There are a number of things that might have influenced the figures I've recorded, so I will divulge such that you can understand my results and take your own opinions on my findings. You could also interpret how the figures might change based on your own circumstances.

When I bought the 330d I had gotten straight out of a 1.4 litre petrol Rover 25 into the 2.9 litre diesel BMW. A considerable increase in power, combined with a differing driving style required between petrol and diesel. I was also doing less extra-urban driving. After it had failed I had to replace the thermostat in the latter months of 2011. All of these factors account for the lower MPG average for 2011.

In 2012 I started a new job, which involved an extended drive to the office, this accounts for the shift in urban/extra-urban percentages. Throughout the year I gained experience and learnt how to get the best out of the car leading to the overall improvement in average MPG.

You may note, on the graph above, a significant dip in the results in December of 2012, this is when my holidays from work are and as such, much more short trips and town driving (or a combination of the both).

I have also noticed that outside temperature makes a big difference to MPG. A general rule of thumb is that the warmer it is outside the higher your MPG, until you have to use air conditioning and it levels out or drops slightly.

In 2013 I have been undertaking a personal mission to increase the MPG I've been getting out of the car. I've been reading up on driving styles and practices and the results have paid off, with the highest average MPG of the three years and with the highest single MPG recorded.


How To Improve Your E46 330d's Fuel Economy


First of all, make sure you are regularly doing a full service on your car, so far I've done three services, one at 124k, 134k and 144k.

The EGR valve on the M57 engine can get significantly clogged with carbon build up, make sure yours is clean and functioning correctly using my DIY guide to cleaning out the EGR valve. To avoid any future build up, use my guide to bypassing the EGR valve completely.

Two more cheap options are to clean your MAF sensor and use a fuel treatment like Comma's Diesel Magic to clean your fuel system.

Finally, a couple of freebies, get all the clutter out of the boot, glovebox, door bins to make the car as light as possible. I'm not saying remove the rear seats or don't have a few CDs in the glovebox, just make sure you're not carrying round your full detailing kit etc.

Make sure your tyres are correctly inflated, and check them regularly (once a month), a couple of degrees change in ambient temperature can make quite a difference to your tyre pressure.


How To Change Your Driving Style To Maximise MPG


I'm guessing, like me, you didn't buy your 330d to drive it around like your Nan, if you wanted the best fuel consumption you'd have gone for a 318 or 320d right?

Thankfully there are a couple of things you can do to improve your fuel economy without confiding yourself to the slow lane.
  • Be analogue not digital
    • Don't stand on the brakes and/or accelerator, read the road ahead to avoid stop start driving. Quite often, even in commuter traffic, if you leave a bigger gap to the car in front you can usually get away with not braking most of the time. When you see the car 5 or so in front indicating to turn, ease off the gas.
  • Use cruise control, where sensible (motorway), to maintain constant speed
    • Again read the road ahead, if you're approaching a down hill you might be better off to turn the cruise control off whilst still on the flat, then use the hill to gain speed.

Conclusion


Excluding the OBC readings, my findings are a fantastic result for BMW. A car over 11 years old with over 150,000 miles on the clock, and the MPG is continuing to rise.

In fact, I have achieved MPG figures above the official combined number from BMW, 44.2 vs 42.2. At 44.2 MPG a full tank of fuel will last you just shy of 600 miles (I managed 596). It is my aim this year to achieve over 600 miles to a tank, which I think is entirely possible even with urban driving percentages as much as 40%.

Would I recommend the 330d for fuel economy? Yes, you simply can't buy anything from a premium brand of that age, that price with the same outstanding performance and driving ability.

If you have any questions do let me know in the comments section below.

What's the best MPG you've achieved from your E46? Got any tips not covered above for improving MPG?