Fuel sulphur is an important factor that affects conversion of NO to NO₂ on the oxidation catalyst and hence the efficiency of CRT.  Fuel sulphur lower than 30-ppm has been found necessary to maintain the functioning of CRT at an acceptable level. In Europe, where low sulphur fuel is available several thousand vehicles with CRT are in operation. To achieve the best performance of CRT, the following conditions should be met:

• Sulphur-free fuel (sulphur <30ppm) is necessary to prevent catalyst poisoning
• For best performance temperature should be in the range 250 – 450º C.
• The / soot ratio should be adequately high otherwise available will be too low to oxidize soot.