I called uo Compressor Works (mfg of R4's) and asked about the sump. They insist it is sumpless. They said, for proper lubrication, there must be proper amount of refrigerant/oil mix and PROPER FLOW. I said there is a cavity in the bottom of the R4 that can hold oil and he says there may be 1/2 to 1 oz of oil in there. Anyway I am just going by what I see and I am sure Compressor Works is right. Maybe that 1/2 moon thing is a counter weight., but, if there is oil which touches the half moon, it will work as an oil slinger.

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85 300D turbo pristine w 157k when purchased 167,870 July 2025
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked