Hi, first time poster in the Mechanics area (I'm usually up to no good in the C&V arena). I had the opportunity to work on a fairly recent vintage (at least for me) bicycle, and flip/flop hubbed Critical brand single speeder. It had some cheapy plastic pedals, which one of them was really rough, spinning wise. After desperately trying to pop the end cap off, with no success, and very recently ruining another bikes pedal trying to pop off what appeared to be and end cap (it was not) I decided to use the "flush and oil" method. That is to say, I ran some degreaser thru them, drained them, and used some 3-in-1 oil (which is what I had around at the time) and dripped a ample amount into them, and stood them on end, leaving gravity to do most of the work. Well, a few days later, after leaving the pedals pretty much untouched, I happen to notice the end caps were oily... huh? And, finding a smaller/thinner bladed screwdriver than I usually have around (don't tell her, by I borrowed from my wife's tool box) I was able to get under the edge of the cap and pop it off. The oil residue clued me into the fact that the caps weren't molded in, or glued in, as I had imagined they were. Where the cap had a "key" or cut out notch (to allow it to slightly compress when snapped in place) a small amount of oil had seeped it's way thru on one of the pedals. If I hadn't procrastinated, I would have never uncovered the fact that the caps did indeed pop off, providing access to the end nut. Procrastination once again rules the day!

Tiny pin hole in the plastic cap. + a needle tip grease gun and you can flush out old grease pushing in new.. excess will come out on the inside end, where it attaches to the crank-arm.

If they are cheap dump them they are disposable items really like tyres, better quality ones can be rebuilt installing new bearings both ends DE & NDE, some have caps at NDE some do not, many years ago there was a little cover with two screws to allow access but not now, cheap ones have no seals oil will lost very quickly, you need to think is it worth the effort.

Thanks, OP. That's a great tip.