I just replaced my fuel pumps and filter on my car yesterday. The fuel filter was three years old. The old gas goming out was filthy. My mechanic suggests on my caer to replace the filter every 20k miles. Since this setup basically gravity feeds fuel from the bottom of the tank, does that mean my tank should be pretty clean and my filter takes the hit or is there going to be a build up of nasty crud at the bottom of the tank? Should I consider removing the tank and cleaning?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual