I'm still driving my '96 Ford F250 diesel automatic. It's never been to a mechanic although I've changed out several things in the back yard myself, like a radiator and water pump. It's pretty simple to work on.
On the road solo, I can make 21mpg at 70mph.
On the road towing a travel trailer, I can make 14mpg at 60 mph.
When I bought the truck 22 years ago, diesel was cheaper than gas. Nowadays, gas is cheaper than diesel. And to make things worse, I read a discouraging article the other day indicating that due to the high pressure being put on diesel supplies as other countries catch up with our modern life style, the price of diesel will becoming increasingly expensive compared with gas. It seems that most of the world favors diesel, so more pressure on its price is being forecast. I don't like the trend, but there it is.