Ford started producing its 8N tractor in 1947 and continued producing it through 1952. As of 2010, it remains the best-selling tractor of all time. Ford 8Ns are still in use and with proper maintenance can last for years to come.
According to the Ford N-series tractor manual, use of 10-weight motor oil for temperatures between minus 10 and plus 10 degrees Fahrenheit, 20-weight motor oil for all temperatures between 10 and 90 degrees and straight 30-weight motor oil when the temperature is above 90 degrees.
When 8Ns were built, multi-grade, high-detergent oil did not exist, and they were designed to allow dirt to accumulate in the bottom of the sump. Modern multi-grade oils are engineered to keep dirt in suspension and make oil changes easier. Once the sump is flushed and cleaned to remove built-up dirt, the process no longer needs to be repeated with any regularity when using a 10-30 multi-grade oil.
For its 8N, Ford specified mild EP gear conforming to Ford specs M4864A (SAE 80) for temperatures below freezing and M4864B (SAE 90) for temperatures above freezing. This conforms to modern-day API gear oil designation of GL3.
