"Thomas Borchert" wrote

And the modern diesel
engines use less fuel for the same power. Much less. But the engines, at
least the ones certificated, are not lighter. Some are heavier than
comparable Avgas engines.

It can be argued that an aviation diesel can be much smaller than an
aviation gas engine, displacement wise, and still perform the same. The
superior torque of a diesel, plus the longer duration of the power stroke
just seems to turn a prop better. Thus, you can come closer with the weight
comparison.
--
Jim in NC