According to the HF Compressor manual ( This one is the 175 PSI, 21 Gallon oil-less) They want you to open the drain valve and run it for 30 minutes straight as
User manual for Sears Air Compressor 921.16471 - a user manual, servicing manual, settings and specifications ofSears Air Compressor 921.16471 - User manuals and advice for your devices - User-Manual.info
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