Mercedes-Benz is insisting its own air-conditioning refrigerant tests were based on real-life situations and were not anything out of the ordinary, despite claims from other quarters the German authorities have taken their own evaluations to extreme levels. 

The German automaker has set itself four square against a powerful coalition determined to stamp out its use of the r134a refrigerant in favour of the r1234yf alternative, which is claimed to be massively less polluting.

Mercedes-Benz counters the European-Union recommended variant can be highly flammable and has drawn some succor from last week's initial report by German road safety authority, KBA, elements of which however, have also pleased the pro-r1234yf camp.

"We have tests, in real life, in an environment that is not surreal," a Mercedes-Benz spokesman told just-auto from Stuttgart. "We looked at where there is the problem... and where there is a whole system break.

"That is the most normal situation that would break the system and from that point we said let's see what will the gas do. We are happy with our tests as we say it has shown something everybody was not expecting, not hoping for [flammability]."

The Mercedes spokesman added the automaker had "surprised itself" with the nature of the tests concerning r1234yf, one of whose manufacturers, Honeywell, stoutly defended its product to just-auto yesterday but which also questioned the KBA methodology in its own evaluation.

"We have not had any visibility on the test process - our concern is more around what is the test protocol - we have had no [KBA] response," Honeywell Fluorine Products Europe, Middle East, Africa and India managing director, Paul Sanders, told just-auto from Brussels. "We are surprised we [have] not been given the opportunity."

However, the polarised nature of the increasingly fractious debate that has drawn in the European Commission, Paris and Berlin governments, dealer associations, chemical producers, the highest French judicial court and automakers into its web, can be gleaned from Honeywell's insistence some aspects of the KBA testing were "farcical" and spurious.

Sanders mulled the possibility the tests could have involved a catastrophic hose failure with significantly raised engine temperature.

"They increased temperature to a level that does not even exist today," said Sanders, adding: "This is our concern. The risk of these events happening is as close to zero."

But Mercedes is pointing to what it claims is the realistic nature of its own evaluation.

"We don't see it as a very extreme case," said the Mercedes spokesman. "We are convinced our testing [is] real life testing, [it] has proved this refrigerant is not safe in our cars."

The German manufacturer is due to have its appeal to overturn a ban by Paris on its A, B, CLA and SL models in the country next week in France's Council of State, the top echelon of legal opinion.

"We are waiting for the next hearing - until then the situation has not changed," said the Mercedes spokesman. "It is important we get a decision as soon as possible from the court.

"The [banned] cars are growing day by day."