Do you like it? Is it worth the extra cost of fuel? Have you had any issues? What kind is it?
We have three, two Dodge 3/4 tons and a Ford 3/4 ton.
The 4WD Dodge that I have made all sorts of modifications to gets really good mileage - I’ve had it get up to 25 on the highway. It’s also got a ton of torque; I use it in the mountains a lot. In fact, I just broke a mirror on it last weekend creeping through a Jeep trail. I really use that truck hard. It pulls a trailer like it’s not even there.
The other Dodge has a service body on it, and gets surprisingly good mileage for the weight it packs around every day. I rarely put serious highway miles on that one, and it gets about 18 mpg.
The Ford is my husband’s, and it gets about 18 as well. The big Dodge can beat it in a drag race, but it’s close. We have a gooseneck ball in that one for pulling the big trailer, and it’s a lot roomier on the interior. It only has seating for five, so if we all have to go somewhere, we take the Dodge, which seats six all cramped together.
I’ve tried both my father’s diesel SAAB 93s and they’re just great.
Especially the newer one, with its six speed gear box. 50mpg and it’ll keep up comfortably with anything else on the roads, you can hardly hear the diesel rumble either.
I’d love if Mum got one, her petrol Rover 45 is just too thirsty and harsh at anything over or around 60mph.
Well I can, but as it’s a Massey Ferguson 3095 (with after market turbo!), it’d be pointless 
What I can say is that diesels typically require servicing more often - oil and filter and fuel filters are the big three, if you want long, reliable life from one. So if you’re looking at a second hand one, get it checked and look for a service history.
The modern diesels with low sulphur fuel can apparently get longer service intervals, but diesel oil and filters are a bit dearer than petrol equivalents, so it always costs a bit more.
We had a Jetta TDI that we only traded in because it had a lot of non-engine related issues that would have cost far more than the car was worth to us. But it was definitely economical - high 40s to low 50s for mileage depending upon who drove. Our daughter has a New Beetle TDI and she just told me yesterday after her last fillup she was getting 51 - most of her commute is county roads with few stops. So even with the higher cost of fuel, she does very well.