Ford Ranger or similar

that's the first time I've seen 2.0 ltr & gas guzzler in the same sentence 😉😉

Just for info ... I can get close to 24mpg towing my heavy twin axle with my ML350 👍

JK , I just saw online that Practical Caravan are doing a review of said beast . Maybe of interest.🤔.

I had the 2.0 ltr bi turbo in a Ford Edge with the 6 speed auto. Superb tow car for our twin axle Bailey. I didn't really work out the fuel consumption but I can say that it towed for 230 miles on just over half a tank (70 Litre tank). Very strong engine and I believe they upped the power output from my model which was 441 nm torque.

I only changed it  due to wanting a heavier tow car.

Try the ssangyong musso pick up can tow 3ton with good results 

One factor to consider, is that any pickup will be classed as a commercial vehicle and you won’t find private insurance for it. It doesn’t matter even its only ever used for private use. Parking can be a pain in supermarkets and public car parks due to size.

That said, my Nissan outlaw was a terrific tow vehicle and gave good mpg towing, but was a heavy  drinker solo around town.