Which adapter to get

The fastest: the BMW units’ own readings come about twice as often as through any other adapter. On firmware older than 5.13.1 it was slower and reset itself; update it with the OBDLink app.

Revs and speed as often as on the CX or more; the BMW units’ own readings about half as often.

Revs and speed as often as on the CX or more; the BMW units’ own readings about half as often.

Revs and speed as often as on the CX or more; the BMW units’ own readings about half as often.

Every reading the car gives arrives; tiles refresh a little less often than on the fast ones.

A plain ELM327: every reading arrives, tiles refresh less often than on the fast ones. Now and then the data paused for 10–20 seconds, and the first figures took a few seconds longer to come.

The Bluetooth LE one of the three iCar Pro models, and the only one an iPhone can talk to. It cuts long answers short now and then, and the data then pauses for 10–30 seconds, two or three times an hour.

A plain ELM327 clone: every reading arrived whole, long ones included, and the link held steady over 16 drives; tiles refresh less often than on the medium ones.

The slowest we measured: every reading arrives, tiles refresh about half as often as on the fast ones. About once an hour it fell silent and the app reconnected.