Piston engine oil temperature model from David Luff:

Piston engine oil temperature model from David Luff:

Attached is a patch to add oil temperature to the YASim piston engine
model.  This brings to life one of the pa28-161's otherwise 'dead'
guages.  It's a pretty simple 'model' based on temperatures and warmup
times I've observed in the labs on auto engines and run through my
dodgy-memory filter.  It does the job of populating the guage with
something plausible though.