Glad the info is of some use...
Another area is the clutch, the setup for the lower/mid range reels is very similar for the respective size reels..4000/5000 etc things change a little in the Shimano range once you get to the Sustain, Twin power etc (basically the clutch receives more protection). Obviously the best of all is the Stella..
Pic of a Stradic after exposure to water, sand and wind...
If you fish off the beach etc you will eventually get sand under the rotor...on the lower/mid range reels the clutch is more or less open to the elements and the combination will start to cause corrosion...
This can be fixed by disassembling and cleaning each part...this can take a bit of time depending on the state of the reel...on occasion hours
However once done, it will be fine...as long as the parts are still serviceable and functioning
The clutch is fairly robust despite the small springs etc and will normally only fail when it is over oiled or full of gunk rendering the springs useless. Again a good lightweight oil is the go, just a thin coat on the parts/rollers etc..no grease
No need to get too tied up over brands or viscosity...3 in 1 is better than nothing...but ReelX, Super lube synthetic is better if you have it.