What is JASO VTWR?

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Jun 11, 2002
Fort Smith, AR
What is the JASO valvetrain wear requirement? Is it a significant test for oil to meet? It seems that only better oils and synthetics pass it. Virtually everyone lists the GM, Ford, or Chyrsler specs they meet. And those that meet the ACEA or Mercedes Benz specs are sure to list those too. Every Ford I've owned points out in the owners manual that oil used should meet their WSS-M2C-specs, but I've never seen a Japanese vehicle spell out the need for an oil to meet the JASO specs. And then there is Castrol...they just say an oil meets the Japanese "engine wear" tests. [I dont know] Is any of this really important, or just more marketing noise in the system?
The test that you are referring to is the JASO M354-1999 for measuring cam lobe wear. It involves the Mitsubishi 4D34T4 engine which is a 3.9 liter in-line 4-cylinder with charge-air inter-cooling. It is operated for 160 hours at a steady state of 3200 rpms with 10% overfueling. A maximum limit for wear is 95.0 microinches. It is one of the three valvetrain wear tests called out in the Global Engine Oil Service Specification DHD-1.
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