Why does Jag XF 0-60mph time vary?

**Q: I'm considering buying a Jaguar XF 2.7D, and took one out for a test drive last week. It wasn't as quick as I expected, given that Jaguar claims a 0-60mph time of 7.7sec.

I then read the full road test in the March issue of What Car?, and you gave a time of 8.9sec - quite a bit slower. Why the difference?
John Baker**

A: The 0-60mph time of 8.9sec was one we recorded ourselves, using the latest GPS satellite timing gear. There could be several reasons our time differs from Jaguar's official figure of 7.7sec.

First, official 0-60mph times are recorded with a 75kg driver and no passengers. We test cars with a driver and front passenger.

Also, manufacturers submit cars kitted out in basic European trim for official testing. We test the popular trim levels, so any extra equipment not present on the base-level trim will add to the car's weight and harm its acceleration.

All our cars are tested with a full tank of fuel, too, which also adds to the car's weight.

Nevertheless, the Jaguar XF is still quick enough for most people's requirements. It's a fabulous all-round car, having recently won our Car of the Year Award in 2008, but if you want a diesel saloon with a bit more punch, check out the BMW 530d.