Here are the front and back labels found on a Mobil 1 10W40 4T Racing Full Synthetic motorcycle oil container. This oil has a professional ratings from both API and JASO. Its available at many auto parts and department stores like Autozone and Walmart. I've used Harley Davidson oil in the past without any problems, but there are a few reasons why you might want to go with another brand of motor oil for your Harley Davidson motorcycle:
1) Harley Davidson motor oils are only offered in 20W50, SAE 50 and SAE 60 viscosity. The 20W-50 oil viscosity is not recommended by Harley Davidson for use in ambient temperatures below 30.2F and the other viscosity's don't even come close to that colder temperature. The cold temperature limit was 40F for Harley's 20W-50 motor oil, but that was before Harley went with a full synthetic oil and before they axed their 10W-40 motor oil. In colder ambient temperatures it's a good idea to use an oil with a viscosity more suitable for colder weather riding like 10W40. Harley Davidson no longer offers an oil viscosity suitable for these conditions.
2) Harley Davidson oil can be hard to find. Harley Davidson SYN3 motor oil is only available at Harley Davidson dealerships and online. If you need a quart of oil when your away from home it can be hard to find a quart of Harley Davidson SYN3 unless your close to a dealership during operating hours. Other brands like Mobil 1 and Valvoline are much easier to find.
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