The benefits of high-octane unleaded petrol outweigh the extra cost of the fuel, expert tests have concluded.
Thorney Motorsport compared two identical Vauxhall Astra VXRs on the same routes over a four-month period.
Standard Tesco unleaded was used in one, Tesco's 99 Octane brand in the other.
The car running 99 Octane averaged 25mpg during the tests, while the lower-octane fuelled car returned 22mpg. That's an overall improvement of 14 per cent.
Daily dyno tests also revealed that the VXR running on 99 Octane produced 252bhp on average, compared with standard fuelled car's 235bhp.
Thorney Motorsport concludes that it's worth paying extra for the Tesco 99 Octane fuel, because you can go further on a tank.
However, high-octane unleaded is known to have a greater effect on heavily tuned and turbocharged cars like the VXR than it does on lower-spec, naturally aspirated models.