My truck(B3-B) engine is a IND-251.I adjusted its tappets valve clearance months ago.It is very with a very good development now,but these days ago I did a consumption media.First I ran 59 kilometers,refill the tank with 31 liters.Media of=1,9 km/l.Today I did another consumption media.I ran 23 kilometers,refill the tank with 14 liters.Media of=1,6 km/l.Why?Which is the normal 251 consumption?Thanks for the inputs.