"Don't fill with biodiesel at the supermarket..."

[romeogolf]

A colleague has a diesel Audi A3 - I think it's a 59 plate model (all she can tell me is that it's S-line and it's black). This weekend she had the exhaust system looked at as a fault light appeared on the dash.

Apparently, the garage told her not to fill up at Tesco or Sainsbury's because they use biodiesel and this "damages the sensors" - She should only fill up at Shell or BP.

Besides the issue of someone driving 4 miles to work and back in a diesel, is there any truth to this claim that (a) the supermarkets sell biodiesel and (b) this damages the vehicle?

I smell bullst but the PH collective may be able to educate me...