Lubricant deposit and degradation test data are presented for 34 lubricants 29 MIL-L-7808 type and five MIL-L-23699 type lubricants. The compatibility of selected lubricants when blended with lubricants of the same general class was also evaluated. In addition, a brief study was conducted with two lubricants wherein standard 48-hour test data were compared with results using the 100-hour CRC test procedure under Type 1 temperature conditions. All test lubricants were evaluated with the 48-hour procedure at 350 F test-oil sump and 500 F bearing temperatures. Mild lubricant degradation occurred as indicated by sample viscosity change however, several fluids experienced significant increases in neutralization number. Using an arbitrary division point at 80, ten of the 34 lubricants were satisfactory on the basis of over-all deposit rating. 350500 F bearing tests revealed no incompatibility of lubricant blends with regard to lubricant deterioration. The effect of lubricant blending on deposit rating was dependent upon lubricant type and in some instances markedly influenced deposition. Results on four lubricants at 425575 F temperature conditions indicated significant acceleration of oxidative degradation and, with one exception, of lubricant deposition. A comparison of data obtained on ten oils using 48-hour and 100-hour test procedures indicated a negligible effect for test duration under Type 1 temperature conditions.