Hi,

This is a common problem with volume and stereo balance control pots.
Your radio sits above the ashtray and the pots can collect nicotine and other grunge to disturb happy operations. The old solution was to use tuner cleaner sold by Radio Shack and others.

Easy to use: Pull the knob off the offending control, spray with the nozzle tube directly into the center shaft where it goes through the support bushing, and work back and forth as you did. It will clean and lube usually with good results without having to remove the radio.

Rat Shack is kaput and looking for new sources for tuner cleaner,
check this link with several good options.

https://www.amazon.com/s?k=radio+shack+contact+cleaner&ref=nav_bb_sb

Walmart carries CRC contact cleaner about $10.
Amazon offers WD-40 contact cleaner for $8 non residual cleaner
DeOxit has a few options at steep prices.

I still have old fashioned tuner cleaner here, so I haven't tried this stuff.
but I'd try the CRC or WD-40 contact cleaners first.

Good luck, Bill