The development of a liquid-phase micro panel coker and a vapor-phase micro panel coker is described. The devices are intended primarily for use in screening synthetic lubricants on the basis of deposit formation in instances where only research-size sample quantities are available. Each model requires less than 75 ml of sample per test and is capable of operation to 1000 F panel temperature. Both micro coker models were utilized in an experimental investigation of the effects of lubricants, panel temperature, and dry and moist air on lubricant deposition. In addition, the liquid-phase micro coker data are examined in comparison with full-scale panel coker and bearing deposition test results.Presented as an American Society of Lubrication Engineers paper at the ASME/ASLE Lubrication Conference held in Atlantic City, New Jersey, October 8–10, 1968.