Harley-Davidson motorcycle engines are air-cooled, which sets them apart from many water-cooled engines. Air-cooled engines run warm and therefore require a higher viscosity (thicker) motor oil. Harley-Davidson has made nine different types of engines, starting in 1929. Each Harley-Davidson model may have a different oil recommendation, and other variables exist: "Refer to your Harley-Davidson owner's manual for the proper SAE grade recommendation based on the climate and temperature range you ride in," according to the Harley-Davidson official website. Harley-Davidson recommends the use of its own Harley-Davidson H-D 360 motorcycle oil, made of 75 percent premium mineral oil and 25 percent performance additives.
Harley-Davidson recommends SAE 20W50 viscosity grade oil for "all temperature conditions," according to the Harley-Davidson website. The SAE 20W50 oil covers the biggest range of operating temperatures and is ideally used in ambient temperatures ranging from 60 to 80 degree Fahrenheit.
Low temperatures, those of 40 degrees Fahrenheit or less, call for Harley-Davidson SAE 10W40 H-D Motorcycle Oil. Harley-Davidson classifies this oil viscosity as "appropriate for low temperature climates." The SAE 10W40 H-D Motorcycle Oil is formulated to guard against low-temperature problems such as erratic idle and lack of power.
Harley-Davidson recommends SAE 60 H-D Motorcycle Oil for ambient temperatures above 80 degrees Fahrenheit. SAE 60 H-D Motorcycle Oil is formulated to prevent engine overheating in high temperatures. Since Harley-Davidson engines already run warm, it is important to guard against overheating by using the proper oil in high-temperature conditions.
