105 drinking a lot of petrol

[Ristov105]

Hi guys I have a 105 petrol 4.5 I’m lucky to get 450kms out of both tanks please help me out thanks in advance

 

[weblife]

Wow. I have a 98 105 Petrol 4.5 and I get around 750 which equates to close to 20L/100km or 5km/litre or 11.7mpg.
My best so far is 16.8L/100km or 6km/L or 14MPG or 850ks on the tank if I drive it like a granny (and I mean averaging 80km/h or less just cruising through the countryside)