well I must be the exception, I have an extension pipe (1mtr of 30mm waste pipe) which saves bending down, used all day and it only needed filling twice, which at around £20 per 5ltrs, I reckon worked out to around £5 worth if that, the BIG DIFFERENCE is that although the smoke smells weird, you dont go home with a stonking headache which you do (or I did) when using a petrol engine,
the difference is, no noise, so alot of places that may not want the drone of an engine being rev'd all day may well give you that permission,