The issue of whether carmakers can specify servicing techniques is under investigation following a complaint from a Smart owner who was told non-franchised work would invalidate the vehicle’s warranty.

The Automotive Distribution Federation is seeking legal advice on the case, in which a Mercedes dealer allegedly quoted £180 for a ‘simple’ service.

The owner was told the warranty would be invalidated by non-franchised servicing, because suction equipment is needed to change the oil as the ForTwo has no sump plug.

According to the ADF, the customer was quoted £70 for the same service by an independent garage which said it would remove the sump to drain the oil.

Smart has requested more details to pursue the matter, and says inexpensive suction equipment is available to independent garages. Its spokesman says it does not dictate labour rates, but its average is £59 per hour.