First of all, have you seen this article from the BBC?
Secondly, I was interested to hear that the Government will be trying to produce more realistic mpg and exhaust emission tests. The thing is though, what is normal driving? About thirty years ago, I had an Austin Mini 850cc petrol. Up here in the Midlands it reliably returned about 45mpg, almost wherever I went. But, when I had a spell living in London, this then dropped down to 27mpg, but immediately recovered once I got out of The Smoke of London. So, which would be considered normal motoring conditions for the UK ñ the stop-start misery of London, or the relatively easier conditions in a modern UK city, or maybe out in some rural town?
Today I have a 1.6 diesel Octavia. We have owned her for three years and the average mpg has settled at 56mpg, which represents the reality of short stop-start journeys in an urban environment. However, when we head out on a cross country trip, I would expect to see 64mpg on the readout, and brim-to-brim filling has confirmed the accuracy of the electronic readout. Hit the motorway though, and I would still expect to see 65 or more mpg, unless Iím driving in bad weather. Sorry, but all of the lights, wipers, demisters, etc., eat up fuel! But a trip around the Wolverhampton ring road will drag the fuel consumption down to under 40mpg. Hardly surprising, as you will hit a red light at almost every other set of traffic lights, and Wolverhamptonís highway engineers love their traffic lights! After each of these, you have to accelerate hard just to slam on the brakes at the next one. A few weeks ago though, I had a business trip down to London, on which I averaged 66mpg for the whole trip, even though the section in London was a match for the Wolverhampton ring road. Which brings us back to the unanswerable question, what is average motoring in the UK?
Hello David. Many thanks for your thoughtful e-mail. I had already been forwarded the BBC emissions comparison report by editor Ian Robertson, and a rather long-winded and, I feel, not particularly clever comparison it is. I don’t think it really adds to the understanding of emissions, because the petrol car in question is something of an exception, and not the sort of petrol versus diesel comparison that is relevant today. All it really exposes is how far the various EC regulations have come, and how much cleaner all cars on the roads are today, compared to what they were 15 years ago, but it’s not really a good comparison of petrol versus diesel today.
What is “normal” driving, you ask, to which there is no answer, as you say. To be fair, it exposes the problems of making valid estimations of fuel consumption and emissions, and just why “official” figures for both will always be (justifiably) open to criticism. I don’t think the new RDE real driving emissions tests are going to add a lot to the picture, and there’s no real big step forward, because on-road testing will always be open to variations of driving style, traffic density, average speeds, and the skill and style of the driver.
You write “Hardly surprising, as you will hit a red light at almost every other set of traffic lights, and Wolverhamptonís highways engineers love their traffic lights. After which you have to accelerate hard, just to slam on the brakes at the next.” But do you always need to accelerate hard and slam on the brakes? No, is the strictly correct answer, but the pressures of heavy traffic generate this style of driving, and it adds very little to the speed of progress of traffic. Bring in some genuine technological assistance, with linked/phased traffic light systems, all aimed at persuading drivers that maintaining an average speed of 30mph between sets of lights gives you a clear run; with all the lights on green, and intelligent reactive traffic lights that give you a “green” when there’s no traffic waiting from the left and right, and we might make some progress. All this vast amount of new technology to stop you running up the rear end of another car when you lose concentration, and perhaps slip out of lane in front of somebody else (who is overtaking in your blind spot) is all very well for accident prevention. But what you really need is disciplined traffic in two or three lanes, all happily and steadily progressing at 30/40/50mph, knowing that there’s nothing to be gained by overtaking. What really ticks me off, to use the polite expression, are the people who attempt to overtake you when you’re going around a roundabout, or out-brake you when you are slowing down to enter a roundabout, when the lanes are narrow, and when it’s just too easy to obstruct such press-on drivers. I’ve been there and been hooted a few times, because such people seem to think you should be aware of them in your blind spot, and are unappreciative that you may not know the road as well as them, and which lane of an exit road is the best one to take.
From the mpg figures that you have quoted, you’re quite an economical driver David, and that’s meant as a compliment. But do you feel you get pressurised by other drivers into driving more aggressively in town and heavy traffic? I’m old and (hopefully) wise, and I tend to take it a bit easy in such situations, as I reflect on the fact that I’m possibly a calming influence, and it doesn’t worry me too much (although it does annoy me!) when some people think I am getting in their way. It adds so little to journey times to take it a bit easy, add another car length to the distance from the car in front, and reduce the likelihood of needing to brake hard, and then use precious fuel to accelerate up to speed again. Some of my most memorable driving experiences are still of driving in the USA, around big cities like Chicago, where three lanes of traffic flow along steadily, all at the same speed, with very few aggressive types switching lanes to gain a few yards. You only have to watch the way some drivers switch lanes back and forth between two lanes in heavy UK motorway traffic, hoping to gain some advantage that often doesn’t ever materialise, and it’s all so utterly pointless. Funnily enough, I have had few problems on the M25, and usually find it quite a relaxing place when there are no real hold-ups, but perhaps I’m lucky and avoid the worst times for traffic. I just look for the quietest lane and try to stay there, keeping the biggest distance I can (within reason) between the car in front and the car behind, knowing that space is a great buffer against someone doing anything daft, and that a steady speed with no braking, be it a bit faster or slower than I might wish for, is the most economical and stress-free speed.
I haven’t answered your question, because there is no answer I’m afraid. Best regards,