The conclusion from our tests was emphatic: although all but one of the superfuels we tested delivered some mileage benefit, none was worth the extra money in terms of the extra mileage it delivered.
The biggest improvement recorded was with Tesco Momentum unleaded, which delivered 45.4mpg as opposed to 44.5mpg when we ran the Polo on standard Tesco fuel an efficiency increase of 2%. However, this was still a long way off the claimed potential improvement of 17.25%, based on Tescos own tests in a supermini, and did not justify the 5p per litre extra charge, which is 3.7% more than the standard Tesco fuel.
The worst performance we recorded was with Total Excellium diesel, which delivered worse mpg than standard Total diesel.
Average economy fell from 48.5 to 48.2mpg when we used Excellium, a drop of 0.6%.
How far can you go? See how much farther regular fuel can take you on the cash saved over superfuels. Click hereWhat the fuel firms say
Despite our rigorous test procedures, BP, Esso and Total all challenged our results, pointing to their own research over millions of miles.
However, even if you accept the official claims, only Tescos demonstrates an improvement in fuel efficiency that outweighs the extra cost of buying the superfuel. All the other official figures deliver smaller mpg gains than the extra cost of buying the fuel. BP, Esso and Total argue that the performance, emissions and engine cleaning benefits of superfuels should also be taken into account when considering the additional cost.
Total would not comment on the fact we recorded worse economy with
Excellium diesel than its standard diesel. Instead, a spokesman stood by its claimed figures, citing extensive fleet tests.
In contrast, Tesco promised a review of its claims which are by far the highest of any fuel maker (see table, left). A spokesman said: We are concerned that What Car?s test results are significantly different from ours. Our clear goal is to provide accurate information to our customers on the real world benefits of using high octane fuel. We are carrying out further independent testing.
What Car? says
Although the superfuels tested here advertise economy benefits among their advantages, none of them delivers enough extra efficiency to outweigh the additional cost.