Timing of the injection pulse(s) and then the addition time before the fuel burns
has a key effect on diesel fuel economy.

Timing has already been retarded from optimum to reduce NOx.

Cetane rating only partially measures this,
but certainly the easiest step for an owner to experiment with is to add an aftermarket additive Cetane improver.

Diesels are only around because
the first prototype engine ran SO MUCH better on peanut oil
than talcum power sized coal dust, which is the “free fuel” that Rudolf Diesel’s coal miner uncles urged him to build a engine for.

Sometimes it seems the government is trying to make owning a diesel such a pain that you go into despair and jump off the stern of a fast moving ship into near freezing sea water.