9.5 average is not that bad for large petrol car. But if you are traveling often, cheapest solution probably will be 1.4/1.9 SDI Seat Ibiza or Cordoba. They are very cheap compared to a VW but are as good and reliable as a VW.

If it's the Ibiza it has 3 cyl engine that gets something like crazy 3.5/4 l per 100 km highway. The cordoba is 4 cyl but gets almost same mileage. I had a 1,9 cordoba and with 1 tank I could go 1200 km highway without problem or 800 city.

Only issue is diesel can be very expensive to maintain and to repair if something goes wrong.

And if you search for a petrol you won't find anything that gets better than 5.5/6 l on the highway so your save will be minimal and almost not worth it to get a 2nd car.