The Fiat 500 from 1957 got 43mpg. Imagine what could be done, if car manufacturers were not focussed on the lease market, meeting the newest emissions regulations (more relevant in Europe), and filling cars with electronic toys.
Yep, there are modern engines that will do that. I was using the example of an older engine, because they are generally much more fixable (which was OP's original point).
Yes, modern engines are optimised for fuel and emissions efficiency to within an inch of their lives. This was my entire point - we could move a couple of people in a Fiat 500 and get 43mpg, in 1957. Without the incentives I mentioned in my first post, we could easily make an engine much more efficient than that, and fixable.
As you ignored my comment on our other discussion, and continue the conversation here - I also assume you have electric heating and hot water at your house. After all, everyone needs to do everything possible to reduce fossil fuel usage, right?
No current company makes any of their modern cars deliberately easy to work on. No matter the %, the fact is you can get a car from VW, BMW, Daimler, Hyundai, Nissan and so on.