crud/residue/dregs on the tub's inside walls might be st
There is crud/residue/dregs on the tub's inside walls behind the basket that rotates too. With a modern FL washer there is not much water used, most of the stationary plastic tub just gets "splashed" with water; ie it does not sit in water.
With boats I have seen that the bilge has a gasoline or diesel leak, 3 decades ago I dumped several gallons of 409 cleaner and let it sat, then pumped it out. On a very hot day one can still often get a whiff of crud decades later.
There will be always traces of the crud clinging to surfaces. The drop in smell happens with each cleaning one does, but unless it is scrubbed out there can be heavy stubborn dregs/residue that lingers.
In rebuilding a FL washer; there is often a scum line above the highest ever water level due to splashing. In old machines with a metal tub that rusts, one can have fuzz from clothes "stuck" on rust deposits right at the scum line. In a modern FL washer; some have screws on the back side of the basket that collect a wad of fuzz from clothes, and this crud absorbs the dregs too.
With all the great cleaners folks have mentioned, there can still be dregs/crud high up on the tubs walls that are just splashed hardly ever. Thus the bottom of the tub can be super5 clean and the upper walls still with areas of thick sticky diesel residue that will take many washes to remove.
Here I have a vacuum cleaner that was used to vacuum up some dried dregs dried chunks in a diesel fuel tank. Now the vacuum smells like diesel when it is run. I took the entire vacuum apart, motor, fan's rotor and stator. The metal parts were cleaned in parts cleaners and degreasers. The remaining smell is in the plastic filter holder, the smell is in the plastic! will all my cleaning an labor spent, there is still a trace of diesel smell.
Thus with a plastic tub washer, the plastic itself can absorb smells. The Odor/smell gets into the plastic's skin. Thus a bloodhound could find your washer in a land fill 100 years from now and detect the diesel smell in the parts per billion level.
Things like "you should have some rags in the cylinder so that when the machine goes into spin, the detergent solution spun out of the rags will spray onto the upper part of the outer tub to help clean it"
are great, you want to get the cleaners to the upper tub areas where there is just splashing.
Plastics vary all over the place in the absorbing of odors. Folks ability to sense smell varies too. In Katrina, many folks threw away there refrigerators because their food rotted and the smell got into the plastic liner.
With a California Refrigerator, I once had some special frozen epoxy in the freezer. Somebody shut off the breaker to the unit by mistake and the epoxy thawed out. This unit then became filled with epoxy smell, totally unusable for food too. Ten years later one could smell the epoxy. We left the unit outside with the doors open for an entire first summer with the sun directly on the plastic to remove much of the odor.
