Kid:I bought a Mitsubishi Fuso truck for my business a few years back and it came with the 140w gear oil. The truck came from California and the service manual stated that the heavier weight was for year round sustained hot climates(100 plus deg) and heavy loads. I know this is an apple and oranges comparison but the same may hold true for our trucks.I'm sticking with the 75-90w mobil 1 synthetic.
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