Diesel Trends 9
PC-9-Building a Better Oil

The ASTM Proposed Category 9 (PC-9) has been under development for the past 18 months. It represents a significant improvement in engine oil performance and will be required for diesel engines equipped with exhaust gas recirculation (EGR). These new engines should hit the U.S. marketplace by mid 2002. It is anticipated that EGR-equipped engines will require oils that are better than the API CH-4 oils currently available in the U.S. in terms of soot handling, lead and copper corrosion protection, and oxidation control.

There are three new engine tests and one new bench test proposed for PC-9. They are: the 300-hour Cummins M-11 High Soot Test, the Mack T-10 test, and the Caterpillar 1Q test.

M-11 is a 300-hour version of the current 200-hour test. It will be used to measure an oil's ability to protect the boundary lubrication areas in the engine, particularly the valve train, under high soot-laden conditions. The test alternates between a 50-hour soot generation phase and a 50-hour wear phase. The EGR rate during the soot generation phase is typically 14% to 15%, and must be 8.5% to 9.5% during the high-output wear phase.

T-10 measures multiple engine oil performance properties. It tests ring and liner wear, lead-bearing corrosion, and high-temperature engine oil oxidation. The T-10 engine is an EGR-equipped Mack E7 V-Mack II engine. It is a 300-hour test, 200 hours shorter than the current T-9. Even though it is shorter than the T-9, it is more severe due to the addition of the EGR. The test includes a 75-hour soot generation cycle followed by a 225-hour wear cycle. The EGR rate during the first phase of the test is not controlled, but runs about 15%. The EGR rate during the wear phase is controlled to about 17% using O 2 sensor readings.

Since the T-10 runs significantly hotter than the T-9, it has been proposed as an oxidation test by the EMA for PC-9. It would replace the Sequence IIIE, which is used to measure an oil's ability to protect against oxidation in the current CH-4 category. Final details have not been worked out regarding the use of the T-10 to measure an oil's ability to protect against oxidation.

If the T-10 is not used as an oxidation test, the new Sequence IIIF test could be added to PC-9.

Caterpillar 1Q is a single cylinder Caterpillar test engine. The test runs 200 hours longer than the current Caterpillar 1P, and appears to be a more difficult test, challenging the oil's ability to protect against high-temperature piston deposit control. The test runs under steady-state conditions for 504 hours, with an EGR rate of 17%. The test stand is similar to the Caterpillar 1P used for CH-4, but it uses a different piston and ring pack.

Two new bench tests have also been proposed for inclusion in PC-9:

1. An elastomer compatibility test using four different seal materials: nitrile, polyacrylate, silicone, and fluoroelastomer. The test compares the seal compatibility performance of the candidate oil to the performance of a known reference fluid. To pass the test, the candidate must provide equivalent or better performance than the reference in terms of volume change, hardness, tensile strength, elongation, and reversion.

2. A low-temperature viscosity requirement for used oils. Some oils demonstrate an ability to meet SAE J300 pumpability as new oil. However, they do not pump well in low-temperature conditions and fall out of pumpability specification when they become contaminated during normal field service. Work is ongoing to study this phenome-non. The goal is to determine which PC-9 end-of-test oil samples, and which low-temperature viscosity apparatus and test conditions, are best suited for measuring a used oil's low temperature pumpability characteristics.

Volatility Limits Tightened
Volatility limits for PC-9 are also being tightened. The current CH-4 limit of 17% Noack will be reduced to at least 15% for PC-9. A 13% Noack volatility standard is also being considered. The benefit to this lower limit is that it would harmonize the PC-9 volatility limits with the current ACEA European volatility limits for the top-tier performance categories E3 and E5.

Additional PC-9 Tests
The Navistar 7.3l HEUI, Mack T8-E, Caterpillar 1K, and the GM Roller Follower Wear Test will also be included in PC-9. In addition, the sequence IIIF oxidation test is also to be considered for inclusion. These tests will roll over into the new category using their current CH-4 limits, with no changes.

The impact of EGR on potentially reducing current extended drain interval recommendations is not known at this time. However, the EMA have indicated that their customer base will continue to expect drain intervals equal to, or longer than, the drain intervals they are using in current non-EGR engines. The new API category defined for PC-9 should be API licensable by mid-2002. The following chart summarizes the engine and bench tests required for PC-9.

Characteristic Proposed Test
Piston Deposits (Fe/Al);
Oil Consumption Caterpillar 1Q (EGR)
Ring and Liner Wear; Mack T-10 (EGR)
Bearing Corrosion
Sliding Valve Train Wear; Cummins M-11 (EGR)
Valve Stem/Guide Wear
Piston Deposits (Al); Caterpillar 1K or 1N
Oil Consumption
Oxidation Mack T-10 / Sequence IIIF
Soot, Viscosity Control Mack T-8E
Valve Train Wear (Pin wear) Roller Follower Wear Test
Oil Aeration Navistar 7.3L (HEUI)
Elastomer Compatibility Bench Test
Used Oil Viscometrics SAE J300 Bench Tests
(Low Temp.)
Corrosion Bench Test Current HTCBT
(High Temp.)
Shear Stability ASTM D 6278 Orbahn
Volatility ASTM D 5800 Noack
Foaming Tendencies ASTM D 892

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