up and down fuel economy

[J_Dub]

got a 4wd 95 l300 petrol 2.4 inj

owned it maybe 2 months now
shocking fuel economy
towing maybe get 320ks
no towing maybe get 360ks

but this last full tank I got 470ks

wtf, thats like 30% beter economy

all thats different from the last week is

replaced front shocks as both were seized
engine flush oil/filter change
and I used a different gas station and different company

pretty stoked to get that much more but any ideas why its so up and down??

could using a different gas station/company mean that the 1 i was using have shit gas??????

[nizmo]

faulty oxygen sensor or sticky auto choke, we have had problems with both at work, thanks nick,