The 100mpg challenge: Pushing my 22-year-old Audi A2 to the limit

Given that my Audi A2 was returning 75mpg in normal use, I had idly wondered what I could get out of this 1.4-litre diesel hatch if I tried.

It was a bank holiday Monday, I was in no rush and I was driving from Bicester to Petersfield and back to visit family. So I had a go. Traffic was light, I found the odd van to slipstream and nobody had binned a BMW M3 into a hedge on the A272. The answer, without trying that hard, because I don't like being a 40mph menace, was 94mpg.

I figured I could do better than that. In fact, I thought I could get 100mpg out of it. Which is why I'm on the A34, again, with nearly a full tank of fuel, again, and slipstreaming a truck, again – not so close as to be a nuisance but not so far back that there's no benefit. This time, though, I have a goal, and a Morgan Plus Four with a cameraman hanging out of it for company.

I'm driving from a filling station near my house to the seafront in Lee-on-the-Solent. Snapper Jack Harrison wonders if it's because that's where the hovercraft museum is and hopes we will have time for a visit.

Alas, no (and it's shut on weekdays): it's just precisely 100 miles from where I started, according to a map. I've calibrated the odometer (against motorway kilometre markers) and the trip computer (via brim-to-brim fills) so I know what level of fibs they're telling.

Not very big ones, as it goes, and they're pessimistic ones. If the trip says I've done 100mpg, I'll have done closer to 103mpg. If the trip says it's right, it's right: I'll have used less than a gallon of fuel to cover 100 miles in a 22-year-old hatchback.

I love this old hatchback. To recap, early last year I paid only £500 for it, because it didn't have an MOT. I thought I'd keep it for 1000 miles and then sell so I could write about how you can be paid to drive, but it has become a car I use all the time and can't imagine selling.