Reply To: 1926 series 80

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Unless the oil passages in the crankshaft have been cleaned out, use non-detergent SAE 30. In view of the sludge you found in the oil pan, some may also be in the crankshaft oil passages. Detergent oil (which all multi-viscosity oil is) can loosen up the sludge in the crankshaft and pug an oil passage to a bearing causing failure. For the transmission and differential, you can also use SAE 250 gear oil. A bulk plant with Chevron products should have it. I mix 25% Power Punch with the gear oil. This is an additive made for trucks. It has the consistancy of STP and provides better lubrication when the gear oil is cold and acts as a viscosity stablizer when the gear oil is hot.