The recent improvements to the Aston Martin V8 Vantage reaffirm the car’s position as one of the world’s most exhilarating sports cars.  The process shaved 0.2 seconds from the 0 – 60 sprint, and, it was claimed, also improved efficiency figures.  That may be true, but the new V8 Vantage weighs in with a combined fuel figures of slightly over 20 mpg, with 14.2 mpg on the urban cycle.  It’s hard to use the term “economy” when talking about such a thirsty motor.

The Aston will now reach 60 mph in 4.7 seconds, which is impressive in anyone’s book, but with the fuel economy figures quoted and the current cost of fuel, it’s a costly exercise. 

Nobody is pretending that people with enough in the bank to spend a six figure sum on a car are going to be that worried about the running costs, but in the current climate, when it is only sensible to think about fuel economy? It does beg the question, can you get performance and economy from the same car?

Well, yes you can. But I don’t think we give them enough credit.

Surely the BMW 330d which can get from standing to 60mph in 6.5 seconds but still return combined economy figures of 46 mpg, should be given greater plaudits for it’s achievements?  After all, we’re trying to squeeze more and more from smaller amounts of fuel so why not reflect this in the car’s vital statistics as released by manufacturers?

Many so called premium car makers; Aston Martin, Bentley, Ferrari, Porsche all make great cars that offer sensational performance, but they do so at a high cost in fuel and, you might argue, to the planet.  The Bentley Continental Flying Spur offers very impressive performance figures with 0 – 60 in 4.9 seconds and a top speed of 195mph, but it does so at a combined fuel cost of 16mpg. Yes, I said sixteen miles per gallon.  That’s on the combined cycle, so the urban figure is likely to be nearer 10 mpg.  Even if we call it a gentlemen’s twelve you’re still burning around 45p per mile of fuel alone, that’s at 117p per litre for petrol.

Is it time for performance car manufacturers to get with the programme and start focusing on fuel efficiency? Being green and being fast should no longer be mutually exclusive.

It’s all too easy to pump more fuel into the engine to make the cars faster.  If that is all we’re going to do it may prove cheaper to allow manufacturers to include a nitrous oxide boost to production cars, “sure you can get this little beauty to 60 mph in less than five seconds, just give it a burst of laughing gas, and hold on tight”. 

Another factor that’s crucial to the performance of any car is it’s weight.  Many Japanese car makers are looking at new materials to lower the weight of their cars and in doing so improve their performance and economy.  If this factor was also added to the mix, car makers would be able to release their cars with a performance/efficiency rating. 

At Yourdriving we think its time to publish efficiency/performance stats so that we can see what cars give you the quickest bang for your environmentally friendly buck.

Manufacturers should release a figure with their cars statistics that was derived from the cars power to weight ratio multiplied by their fuel economy.  This figure gives a good performance/economy rating.  The higher the figure the better performance against the cars economy.

There would be three ways of raising this figure; more power, better economy or lighter weight.  Two of the three factors measured would result in better economy, so manufacturers would be better to invest their time in lowering weight and improving economy than just pouring more petrol down the engines throat to increase performance. 

If we look at five examples we can see the figures at work.

BWM 330d

Power to weight ratio of 227 bhp over 1535 kg, multiplied by 46 mpg gives a performance/efficiency rating of 6.8

Bentley Continental Flying Spur

Power to weight ratio of 400 bhp over 2475 kg, multiplied by 14 mpg gives a performance/efficiency rating of 2.3

Seat Leon Cupra

Power to weight ratio of 243 bhp over 1345 kg, multiplied by 34 mpg gives a performance/efficiency rating of 6.1

Toyota Prius

Power to weight ratio of 76 bhp over 1300 kg, multiplied by 65 mpg gives a performance/efficiency rating of 3.8

Lotue Elise

Power to weight ratio of 120 bhp over 785 kg, multiplied by 38mpg gives a performance/efficiency rating of 5.8

As you can see the Bentley is the worst performer, it’s weight and fuel figure being it’s undoing.  Toyota’s Prius gets a reasonable rating, not because of it’s performance, but because of it’s low weight and good economy.  The BMW and Seat are both great cars, with real powerhouse engines, but it’s the Seats light weight that has given it such a good rating, although it’s economy is reasonable for the class of car.  The Elise makes great use of a relatively low power output because it's such a light weight vehicle.

This doesn't take into account the number of seats and therefore weight of the possible passengers, but as all the figures quoted by the manufacturers are obtained in the workshop it seems right to keep everything constant with the workshop numbers.  safety equipment and luxurious finish add extra weight to the cars and this is obviously a factor on the weight of the cars, but that is for the carmakers to contend with.  We're just looking to get the best performance for the fuel consumed.

In the days of shrinking oil supplies and soaring costs of fuel surely it’s time to implement a new metric with which to measure cars relative performances.  If cars were sold with a performance/efficiency rating it would help re-focus the modern requirements of cars, namely getting the most from your fuel.  This would also help guide the public as to which cars were going to give them the best performance, for the right price.

A car’s performance alone isn’t enough to help you decide which model to buy lets include a rating scheme to help people chose the real performers from those that do perform but at a price.

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