I have a old camping cooker from Trangia.
It comes with an aluminum pan (no non-stick coating, just plain aluminum), and when I last used it and made some eggs, due to the cooker being slightly tilted, there is now burned-in oil on it.
It is very hard to remove with mechanical means, even using a mild abrasive cleaner.
Since it is aluminum, I can not use the aggressive grease removers. Is there any advice on how to clean burned oil from aluminum pans?
The ultimate way to remove burnt-on stuff from aluminium is a motorised wire brush. Solid brass is fairly aggressive but manageable (watch out for brass-plated steel, which is too hard). Sets are available with nylon and brass brushes in various shapes to mount in a drill. Brass will scratch up the surface, but you can polish the worst of the scratches out with abrasive cleaner if you really want to.
Before that it might be worth trying the most aggressive kitchen degreaser you can find, sprayed on, left for a few minutes, then scrubbed with a nylon scouring pad. One I've used does slightly soften burnt-on grease, though it doesn't dissolve it.
The manufacturers Bar Keeper's Friend recommend it for use on aluminium, including for burnt-on oil, but I haven't tested it myself.
The degreasers to avoid are the strong alkaline solutions
