Hi all,

Got this VW Golf, failed MOT on CO% and HC.

CO% around 0.8
HC around 400
Lambda around 1.015

No faults stored and live data looks good. No exhaust or inlet leaks, had a new cat a few months ago as it was rattling (that was probably an indication of the problem starting then), performed engine service including oil flush, still the same. Customer has mentioned she has had to top the oil up a bit, tried an oil treatment for worn engines, HC's down to about 350 and CO% still around 0.8, have managed to extract from her the amount of oil she has been using, at least 5L in the past year. Performed compression check, all quite high although 1 cylinder was a little lower than the rest. Vehicle has just gone over the 100k miles and drives really nice, for a VW

I'm suspecting worn engine and the oil usage is the problem, but ive had vehicles burning the same amount of oil in a month and still pass the emissions easily.

Any other ideas?