Besides!

While reduced RPM and lower power extraction have a certain contribution, to the lower fuel consumption, of a glow engine that has been converted to Diesel, the main factor to this is the higher potency of the fuel.

An ounce of model Diesel fuel has nearly twice the BTUs of an ounce of low nitro model glow fuel.

It is this that allows a diesel to make a comparable amount of HP, at similar RPM levels, while using much less fuel to do it.

This does not necessarily mean that we must all run our Diesels at the same RPM, they ran in their previous 'glow' life, but a reduction in fuel consumption should not promote us to running them at very low RPM, as this contribution is only partial.


And as to what Martin wrote; using lower compression to lower the load on the engine's working parts... Running any engine at a lesser load AND at lower RPM (but at proper working temperature - i.e. not too cold), will contribute to its longevity.
But don't some well made glow engines (Jett, for instance) run for over 100 hours at 17,000 RPM and at very high load?


I have no doubt the muffler's back pressure comes deeper into play, as RPM rises further.