If a car stands still for a long time the fuel it has degrades. So it nolonger is even ron95 probably. (Draining the left over fuel and replace it with new fuel is not a bad idea.)
Fuel is not indefinately good. It gets bad just like fruit
Further more you should give the car at least a service because the oilfilter and other bits need replacing.
But your mechanic will sort it out probably.
What was the reason the car stood still for a long time?
This will give a good clue for the problems ahead. I don't think anybody has a 155Q4 just standing around unless:
- he/she can't pay the upcoming bill
- has something nicer to drive? (But then why keep the Q4 at all?)
- The asking price is much to high
- Lost his or her driving licence
- The car was part of the goods of a deceased family member and it took some time to sort it all out.
- the car was crashed and it took some time to get it "fixed".
I hope it is okay but have it closely inspected if you haven't done so already!
I hope it is in good condition for your sake.