BMW 535d Touring M Sport

Road test editor Oliver Marriage hits cruise control to manage M-way returns

In order to see how far we can improve our economy, first we need to know what fuel returns we’ve been getting so far. That’s a simple task, because all of our long-term cars carry log books which are filled out every time they’re refuelled.

And we’ve been highly impressed with the 535d. Not only is it enormously fast, but thanks to BMW’s Efficient Dynamics package – which uses brake energy regeneration to charge the battery rather than drawing power from the engine – it has proved economical, too. Over the last 16,000 miles, we’ve averaged 34.8mpg overall, with this figure rising to 37.1mpg on motorways.

Mind you, expand that out over 40,000 miles, and with an average pump price of 103.7ppl, my yearly fuel bill is more than £5,000. All this from a car that’s totally suited to motorway use – it has a drag factor of just 0.29Cd and at 70mph pulls a mere 1,700rpm in sixth.

I’m not afraid to admit that I cruise at over the posted motorway limit on my 70-mile pre-dawn route to the office. So it doesn’t take a genius to work out that the easiest way for me to get extra miles for my money would be to slow down. But there’s more to saving fuel on motorways than that.

I often travel with a bike rack on the car, the air-con switched on when it’s not needed and am guilty of filling up at pricey motorway service stations. (The highest I’ve seen is £1.12, although I now check out www.petrolprices.com among various other price comparison websites.)

So for the last 2,000 miles, I’ve eased off the gas, kept a very close eye on the BMW’s trip computer and followed the advice laid down by the Government’s Act On CO2 website (www.dft.gov.uk/ActOnCO2), using every technique in the book to minimise consumption.

Dropping below 70mph and looking further ahead to anticipate traffic slowing or vehicles moving lanes means I barely need to use the brakes at all – and pressing the middle pedal is the biggest enemy to achieving good mpg.

Why? BP’s product development manager Brian Macey told us: “When braking, you waste all the energy and momentum that’s built up in the car. It’s far more efficient to coast where possible.” Even though the BMW’s intelligent alternator converts brake energy to battery power, the 535d fared far better when the middle pedal was used as rarely as possible. Keeping to just below the speed limit saw motorway economy rise by more than 10mpg – which, over the course of a year’s driving (40,000 miles in my case) means I’d save more than £1,000, not to mention reduce my carbon footprint by 2.8 tonnes.

But is it all good news? Well, the discipline required to hold a steady speed was made easier by activating the cruise control, and to be honest I soon got used to the reduced pace. I did miss the twin-turbo’s 580Nm of torque, and my journey times increased – but only by about six minutes over the course of 40 miles on the M4.

Most impressively, overall we’ve managed to beat BMW’s official claimed combined figure of 40.9mpg. Our 41.7mpg return isn’t bad given that our offices are based in central London, I travel home in the middle of rush hour and my weekends are filled with short trips, often with the car fully loaded. I’m really happy with the savings I’ve made – so can the other two do any better?

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