BMWZ4 (2009-2016)

How we test ease of driving

To find out how easy a car is to drive, we assess cars across a number of areas from visibility and handling to the layout of the cabin and how smoothly the engine delivers its power.

How we test performance

We test braking distances and whether the effectivess of the brakes fade with repeat use. Performanc is based on in-gear acceleration.

How we test comfort and practicality

Comfort and practicality includes how easy it is, or not, to get in and out of the car and the maximum height of occupants. We also measure road, wind and engine noise and assess how well the car deals with bumps from large potholes to jittery surfaces like cobble stones.

How we test euro ncap

Any car that receives a rating of two stars or less from Euro NCAP is made a Don't Buy. Any car that receives three stars can't be a Best Buy. If a car has been available for more than four years and has not been tested by Euro NCAP, it cannot be a Best Buy.

How we test safety kit

We factor in the safety equipment that’s factory-fitted or optional, along with how well the car protects its occupants and pedestrians in the event of an accident. We also test how easy it is to fit a variety of child car seats.

How we test brand reliability 0-4 years

Our reliability ratings are based on the feedback from tens of thousands of UK motorists, as collected in our annual Which? car survey. We divide all reliability feedback into three age groups: cars aged up to four years, five to nine years, and 10 to 15 years.