I don’t know if cars are the same these days but ‘back in the day’ I never let my car get low on petrol. I was told that an emptyish tank would suck up the grit and sludge at the bottom of the tank . This would imp[air the running of the car. I think I was over zealous, a half empty tank meant a visit to the petrol pump.
When I pray ‘search me, O Lord,’ I imagine Him scouring out my soul. He exposes the sin deep within me which no-one else ever sees. My heart and soul contain plenty of muck and grime which He needs to deal with. My heart needs a good clean out, then my spiritual performance will be enhanced. I pray, ‘Renew a right spirit within me me, O Lord.’