I have the TPMS fitted to my E350 and although I rarely pay it much attention, I have been keeping a close eye on it over the last few days as I have lost a bit of pressure. Mine shows pressure in bar rather than PSI. Whilst I know it is a relatively simple conversion, most airnlines in the UK seem kitted out for PSI and my mind works in PSI. Does anyone know if this can be changed? I can't find a setting for this anywhere. Also, how accurate is it? My tyre had a nail/screw in it about 2 months ago. It lost the head after a day or so if me discvering it and pressure never changed, so I didn't get the tyre looked at. Just done 500 motorway miles and discovered today that this particular tyre was down by 0.4 bar. I pumped it back up and checked it constantly and it hasn't moved again despite doing another 50 motorway miles afterwards, so I assume it was the heat of 500 motorway miles that caused air to escape. I just wondered how accurate it was and whether it could be trusted as an indicator of true pressure.