I was having a bunch of problems with my Shimano Acera shifters, both the front and rear derailleur over the past few weeks. The problems had started really slowly; first I lost efficiency with shifting to my high speed front gear (danced between 2/3), then I lost my 7th rear gear (danced between 6th/7th). After another wipeout, I lost the entire 3rd front gear.
I had cleaned the bike after each ride and applied extra dry chain lube to the chain with no improvement. I tried turning the derailleur adjuster knobs, which worked to get better shifting to the biggest or lowest gear, but invariably, if I cranked it up to the biggest gear, I'd actually lose the small ones, and vice versa. So that simply replaced one problem with another one.
On some advice on this forum, I squirted some lube into my derailleur and a drop or two into the cable housing. I'm not sure if this did the trick, but I just rode my bike today, and everything's totally back to normal and working 100%. No gear dropouts at all.
Was it the lube, or do you think something else did the trick?