Any Advice?

[Chris152]

Hello all, new member here.
Until a few years ago I was a committed Volvo driver - 340, 240 saloon, 240 estate, 850, V70 then another v70 across three decades. Then I moved over to vw Transporter as we needed a van - shame Volvo don't make vans!

Anyway, that's a bit of background. New situation is my son wants a v cheap/ scrap car to work on and learn about mechanics, and will want a road-worthy car for driving once he passes his test.
Yesterday we hit a compromise car that ticks both boxes, having looked over a friend's car - a Volvo 240, preferably estate (so he can camp in the back - I used to do that lots when I was younger).
They look easier to work on than lots of newer cars (easier, certainly not easy for me, I know next to nothing about mechanics), lots of room around the engine etc. plus they look to be a decent investment. We both love them.

But then I looked at MPG on-line, and it seems people are getting around 20mpg?! I'm sure I used to get around 30 mpg from my 240 (I think it was a GLE) auto on average.
Sooo - two questions.

Am I right thinking they'd be good for him to learn about mechanics on?;
and what is a realistically achievable average mpg in a 240, and specifically, which one should we be looking for to get most mpg?

Any advice very much appreciated.
Chris