2010 ML350 Bluetec tire pressure question
 

Hello - I have a 2010 ML350 Bluetec with the original Bridgestone Dueler H/L 400 tires. The vehicle gas cap says the cold-tire pressure should be 32 PSI (or 32-36 on the rear tires depending on the load weight). I just had a servicing at the MB dealer and they reset the cold-tire pressure to 38 PSI on all 4 tires. I asked them about this and they said 38 is correct. Can anyone explain the discrepancy and/or advise what tire pressure is appropriate? Thank you.