In internal combustion engines with manual transmission be sure not to overdo that, high gear and very low RPMs are bad for the engine/transmission due to high

In internal combustion engines with manual transmission be sure not to overdo that, high gear and very low RPMs are bad for the engine/transmission due to high load and minimal oil lubrication, it's also not efficient on fuel, there were local magazine tests done, but I don't have references now sorry. On an automatic transmission the transmission control module will figure out the gear for you at given conditions (won't let you get too low in the same gear) and what you say will be true.