You are right. I used too general term "engine". But brand new engines for initial couple of kilometers burn more fuel than usual. (Not making it up: Do brand new cars use more fuel at first? )
He mentioned that he is getting poor fuel mileage, which i believe is 1) he is measuring it wrong, and 2) He is not aware of 'more fuel consumption' in initial runs.
I don't know the real reason for that. Maybe i have to dig up for more technical answer. Let me know as well if you find it.