....Not sure what they mean buy extreme condition. But I live in the houston Texas area. I pull a 6500 pound tractor about 3 days a week for my side business. I also pull a travel trailer several times a year. So I am not sure what oil to use......
Here you go!
Engine lubrication for severe service operation
The following conditions define severe operation for which engine
operation with SAE 5W-40 API CJ-4 is recommended. Oil and oil filter
change intervals will be determined by the Intelligent Oil Life Monitor™
as noted previously.
• frequent or extended idling (over 10 minutes per hour of normal
• low-speed operation/stationary use
• if vehicle is operated in sustained ambient temperatures below -10°F
(-23°C) or above 100°F (38°C)
• frequent low-speed operation, consistent heavy traffic less than
25 mph (40 km/h)
• operating in severe dust conditions
• operating the vehicle off road
• towing a trailer over 1,000 miles (1,600 km)
• sustained, high-speed driving at Gross Vehicle Weight Rating
(maximum loaded weight for vehicle operation)
• use of fuels with sulfur content other than ultra-low sulfur diesel
• use of high-sulfur diesel fuel
Maintenance and Specifications
2011 Diesel (eco)
Supplement, 5th Printing