Fuel consumption is very high on my Audi A4 engine size 1.8l year 1996 on 1996 Audi A4

what could cause this because I service it on time

3 answers
Exactly which engine is in your car? You give 2 choices. Then post MPG.
seek a diag and have fuel trim read on scanner to determine isssue. you should have eng codes
What is your deffinition of 'service' include? Are factory plugs included. Does it have any exhaust leaks/intake leaks. Best bet IS to have it scanned (live data) to see what's actually going on. Only engine listed on A4 is 2.8L V-6. Is it an A4 Quattro? Automatic or manual trans.?