It’s not easy being green: the Microsoft MPG Challenge

What happens if you drive too slowlyI took the Microsoft MPG Challenge at work today. The basic idea was to learn how to drive a car more fuel efficiently and see how much of an improvement I could make to my MPG (miles per gallon) score. On my first drive around the residential mile-long course in a tinny little Seat car I managed just 24 MPG. After the instructor told me when to accelerate, change gear, and brake I managed 35 MPG, a 46% improvement! Not bad for simply accelerating more gently, allowing the car to decelerate more steadily, jumping from 3rd to 5th gear, and paying more attention to the road conditions ahead.

I had impressed myself, if not the driving instructor, so decided to put the theory to the test on my homeward commute in my Skoda Octavia around the M25. My car’s an automatic so some of the gear-changing theory was redundant. I also drive much of my commute on motorways so dropping to a lower constant speed was pretty much all I could think of changing.

Dicing with death amidst the lorries on the inside lane I activated cruise control at around 60mph, switched off non-essential comforts like air conditioning and sat nav, and put my feet up for the long crawl home. I even emptied my pipe before setting off (to reduce weight) and tuned the wireless to BBC Radio 3 for that authentic octogenarian driving experience. I was strict too. At one point I could have sworn I was lapped by a convoy of knackered army vehicles on their ways to the scrap yard.

Here, after much fevered calculation, are the results:

57 miles @ 60mph average speed at 43.6MPG taking 57 minutes
This consumes 1.307 gallons (5.943 litres) of diesel at a cost of £5.88 (@98.9p per litre)

57 miles @ 48mph average speed at 56.6MPG taking 71 minutes
This consumes 1.007 gallons (4.578 litres) of diesel at a cost of £4.53 (@98.9p per litre)

Quite a difference. So, here’s the good bit:

  • In one trip I’ve saved 1.365 litres of diesel worth £1.35, reducing my CO2 output by 3.7kg
  • Over the course of a year (based on 135 return trips) I could save £364.50 and reduce my carbon footprint by 999kg, just under 1 tonne
  • This would save me having to plant an acre of trees to help clear my eco-conscience

But, here’s the bad bit:

  • Each journey now lasts 14 minutes longer, that’s a 25% increase
  • Over the course of a year (based on 135 return trips) this would mean I spend 63 more hours commuting, that’s an additional 2 days and 15 hours
  • I would almost certainly be crushed to death within weeks by a weaving foreign lorry sideswiping me out of its blind spot, or suffer a massive cardiac arrest brought on by my blood pressure rising with every vehicle that passes me by

Due to a quirk of fate my home and workplace are in very different locations meaning I already spend more than 10.5 days of my life commuting to and from work in my car each year. The thought of passing even more time behind the wheel has very little appeal. Looking at it another way, if someone offered me £364.50 right now to go and sit in my car for the next 63 hours I’d tell them where to stick their gearstick.

So, with regret, much as one tonne of CO2 sounds like a worthy reduction to aim for, I can’t see me adjusting my driving habits any time soon. Life’s just too hectic and, selfishly, I value my time more highly than my exhaust fumes.

Thanks, Microsoft, for the lesson today. You reminded me how to anticipate road conditions ahead and to think about the environmental impact of my driving. But my busy job doesn’t afford me the luxury of driving so slowly and I value time with my family more highly than time inside my car. It’s so true what they say; it’s not easy being green.