Technical High fuel consumption with the 1.4 T-Jet engine

[FirstTimeFiatDriver]

The car is a 2018 Tipo with the 1.4 T-Jet engine and also has a factory installed LPG system.

Recently fuel consumption has reached very high numbers for both petrol and LPG fuels during urban driving, 19 l / 100 km and >20 l /100 km respectively. About a year ago consumption was around 14 l / 100 km when driving with LPG.

• A few months ago there was high LPG consumption. There was no check engine light or engine codes and no symptoms other than frequent refueling. LTFT for LPG had reached -30, but it was normal for petrol. Changing the LPG injectors fixed the problem and LTFT came back to normal.
• A little over a year ago both Oxygen sensors were changed because one of them threw a code.
• Right now there is no check engine light, no error codes (at least according to a cheap ELM327 scan tool) and the car drives fine without any symptoms. LTFT for petrol is close to 0 and for LPG around -5.5.

Any ideas? What could be the cause, what should be checked?