Toyota avensis 1999 consumption

[Xkrtwi]

I have yearmodel 1999 toyota avensis 1.6 4afe and the fuel consumption has been about 15l/100km where to start looking for problem?

[TonyHSD]

That’s almost double of what should be. Start from when and if the car been serviced, run diagnostic, check plugs, air filter, any smoke from exhaust, change garage where you usually fill up, add some petrol cleaner additives, is it cold weather where you are now? How do you drive the car, short trips in town, motorway high speeds ., all these will take you into right direction to find out why your car consumption is higher than usual. 
Good luck 👍 

[Xkrtwi]

I changed the oil and filter 1000 km ago im aware that it burna very small amount of oil due to high mileage. I drive the car short distances to work, the usual temperature here is about -20 degrees ill start by changing the plugs and run a diagnostic