Not an Eco-Warrior? You can still cut your driving emissions — Part Two.


Blimey, what a difference a few weeks makes. Since Part One of this post was published, the UK has seen full-on petrol and diesel shortages, with queues, punch-ups on the forecourts, and petrol stations running dry. Things seemed to have calmed down for the moment, but the situation remains precarious.

So, faced with the possibility of no fuel, and higher prices at the pump, you might consider that reducing your car’s emissions is going to have to wait for a while. You can get back to saving the planet when you’re not worrying about getting to work.

Ah, but here’s the thing: it’s not a one-or-the-other choice. In fact, if you’re sticking with your current car, using less fuel is the same thing as reducing your emissions. It’s one of those rare cases where thinking about your wallet lines up perfectly with protecting the environment.

With that in mind, we’ll look at some of the ways you can do both. We’ve put them in rough order of increasing effectiveness:

1. Less junk in the trunk

Every motoring advice page on increasing fuel efficiency seems to mention this old chestnut: to increase your fuel economy (and therefore reduce emissions), clear out any excess weight from the car.

On the face of it, this makes perfect sense. So it’s a pity it doesn’t work very well. OK, if you’re Tony Soprano lugging around a couple of former business rivals in the boot, then the increased weight will noticeably decrease your fuel economy. But for the rest of us, removing something like a toolbox probably doesn’t make that much difference.

For example, let’s say that you remove 10kg of junk —a fair bit — from your 1445kg VW Tiguan. That brings the weight down by a less-than-impressive 0.7%. Don’t expect that to do anything to your emissions or fuel consumption. Because cars weigh hundreds and hundreds of kilos, small weight reductions only lead to minimal improvements in fuel economy.

By all means try it, but we think you will find there are much better methods.

2. Get pumped up

Part of car ownership 101 is regularly checking your tyre pressure is what the manufacturer recommends. This is because under or overinflated tyres wear faster, don’t perform as well, and are more likely to suffer a blowout.

However, underinflated tyres also increase your vehicle emissions and reduce fuel economy. How much difference this makes is open to some debate. For example, one widely-cited study found that underinflation by 10% (say 29psi insted of 32psi) led to a 4% increase in fuel consumption. On the other hand, Which? magazine found that deflating the tyres on a hatchback by 15 psi (which is an enormous drop) only increased fuel consumption by 3%.

What we can say is that if you’re really trying to lower emissions and increase fuel economy, checking your tyre pressure may be worthwhile. And of course, everybody should be doing it anyway.

3. Not so fast, not so furious

Ah, now we’re talking. Changes to driving style have a huge impact on your emissions and your fuel bill.

If you like putting your foot down on fast roads, just be aware that even modest increases to your speed have a surprising effect on your car’s thirstiness. The technical reason for this is that drag increases in proportion to the square of a vehicle’s speed and the power needed to overcome that drag increases in proportion to the cube of the velocity. Got that? In other words, the engine has to work much harder than you would imagine to get a few extra mph.

Putting it in real terms, going from 70mph to 80mph reduces fuel economy by  a hefty 15.4%. Of course, you do gain some time — over a 100 mile journey at 80mph, you’d get there a whole ten minutes sooner than travelling at the speed limit!

Smoother, calmer driving can also do wonders for your emissions, fuel bill and possibly your blood pressure. It’s pretty obvious stuff:

  • accelerate smoothly, without mashing the go-pedal
  • anticipate traffic conditions ahead to reduce braking
  • don’t hoon round corners
  • shift gear at lower revs, rather than at the redline.

So, essentially, take all the fun out of driving? We’ll leave that for you to decide, but if you normally think you’re Vin Diesel, we reckon that even two weeks of not-so-fast-and-furious driving would see a noticeable difference in your fuel consumption.

4. Use the car less, especially on short journeys

A very effective way of reducing your car’s emissions is — who would have thought it? — not using it so much. Reducing short car journeys has a particularly large effect on emissions and fuel bills, because the engine is running less efficiently while it’s warming up.

Of course, the car is often the fastest or cheapest or easiest way to get around. Sometimes it’s the only practical option. Other times, however, it’s just a habit. Just take a look at these stats from the ever-helpful RAC:

Car use (both as driver and passenger) accounts for only 8 per cent of the trips under half a mile in length but rises to 76 per cent of all trips in the 2 – 3 mile band and 80 per cent of trips longer than five miles in length; above one mile, more than half of all trips are by car.

As confirmed car-addicts, even we were surprised to see that over three-quarters of 2-3 mile trips are made by by car. Fair enough, a proportion of these journeys may be much harder or impossible without a car (school runs, shopping, trips for people with limited mobility). But that surely leaves millions upon millions of journeys where there’s already a viable alternative. Electric bike, anyone?

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