MIL-PRF-21260E
4.3.3.5.1 Four-stroke cycle diesel engine - low sulfur fuel. The oils shall be tested in
accordance with Caterpillar 1N test procedure using low-sulfur fuel. (Only one test is required;
however, the test limits are adjusted according to the number of tests submitted and equivalency
to original limits.) The test results shall meet the following criteria:
1 Test
2 Tests
3 Tests
Top groove filling, % avg. max.
20
23
25
WDN, demerits, avg. max.
286
311.7
323.0
Top land heavy carbon, % avg. max.
3
4
5
Oil consumption, grams per kilowatt hour
(g/kW-h)
0.5
0.5
0.5
Scuffing, piston/rings/liners, avg. max.
none
none
none
Stuck rings, avg. max.
none
none
none
4.3.3.5.2 Four-stroke cycle diesel engine - higher sulfur fuel. The oils shall be tested in
accordance with Caterpillar 1M-PC test procedure using high-sulfur fuel. (Only one test is
required; however, when three or more tests are run, one test may be discarded and the average
determined from the remaining test results). The test results shall meet the following criteria:
1 Test
Top groove filling, % avg. max.
70
WDN, avg. max.
240
Ring side clearance loss, millimeter max.
0.013
Piston ring sticking
none
Scuffing, piston/rings/liners
none
4.3.3.5.3 Two-stroke cycle diesel engine. The oils shall be tested in accordance with
ASTM D5862. (Only one test is required; however, if more than one test is run, the test limits
are adjusted according to the number of tests run, maximum of three tests, and equivalency to
original limits.) The test results shall meet the following criteria:
1 Test
2 Tests
3 Tests
Average ring face distress, demerits (max.)
Fire ring, avg.
0.33
0.34
0.36
Nos. 2 and 3 compression rings, avg.
0.28
0.29
0.30
Broken rings
none
none
none
Cylinder liner area
Avg. liner distress, % area, avg. max.
60.0
63.5
65.0
Port plugging, % area, avg. max.
Avg.
2
2
2
Single cylinder
5
5
5
14
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