I am a new HD owner of a used 2003 FLHTC-I. I am trying to get a handle of the oil requirements. According to the original owners manual I should use HD brand or I can substitute with a same weight oil for diesel engines. The trouble is, I cannot locate 20W-50 in a API Service CH-4 (Diesel) without buying the HD brand. From the sound of it, most are ignoring the Diesel requirement and using fossil or synthetic 20W-50 oils without problems. Is a 20W-50 API Service SL or better changed every 3000 to 4000 miles adequate? Why are the diesel additives suggested for a gasoline engine? I can easily find 15W-40 CH-4. It would seem to me that the correct viscosity would be more important than additives that are designed for a fuel that is not used.

 

You can put 20w-50 diesel oil in your bike "in a pinch". It is not recommended for normal oil changes. Either use HD 360, if going with conventional oil, or use a synthetic MC oil. I personally use 20w-50 HD 360 in the crankcase and HD formula+ in the primary and transmission. I change engine oil every 2500 miles and change primary and transmission oil every 5000 miles. If you do the math, and with the cost of synthetic motor oil, you will save money using HD 360 and changing every 2500 vice 5000 miles.

 

why not motorcycle oil that has additives for higher sustained heat?

 

You can use any 20W50 synthetic Motorcycle oil AMSOIL MCV 20W50 works great. so does Mobil V Twin. Redline is an automotive oil, not formulated for Motorcycle use but a lot of folks use it and like it.
You can use Petroleum oil of the same weight but you would be far better off with a synthetic. Up to you. I use the AMSOIL MCV in the motor and primary but use AMSOIL SVG 75W90 Gear oil in the trans and am very satisfied with the performance.

 

That is pretty much what the manual says. My interpretation is that HD 360 is a cracked crude product that must have some diesel type additives. The manual recommends 8000 mile oil changes. The research I have read indicates that typical motorcycle designed oils that are not synthetic lose viscosity at about the same rate as automotive cracked crude products. Synthetics last more than twice as long but I intend to change every 3000-4000 miles since I don't put many miles on per year. Synthetics and the MC oils don't indicate that they contain diesel type additives yet they are used commonly without problems. So what is it with the diesel additives?

 

Why must it be a synthetic. I understand that synthetics will last more than twice as long as cracked petroleum products, but I intend to change my oil every 3000-4000 miles instead of the 8000 mile recommended with the HD 360. Can the additive that HD uses be that much superior to the typical additives in an API service rated SL oil to double the service life?

 

To my way of thinking, the oil is the cheapest part of the investment. Synthetics are far superior in every way except cost. They will poor freely at -75 F and still function perfectly at over 600deg F. They have none of the contaminents that naturally occur in Petroleum oils thus the engine stays cleaner, runs cooler and will require less maintenance.

The top oils like AMSOIL and Mobil have anti corosive additives that are extremely important if the bike sits a lot or is in a climate with large temp changes where the metals sweat.

I recently read in a lubes and greases magazine a statement from a lube engineer, He stated that with the state of the art of synthetics today he can't imagine why anyone would run a petroleum oil in an engine In the end the choice is still up to you.

 

I use Mobile V-Twin in the engine and primary. And Mobile synthetic 75/90 gear oil in the transmission.

With the heat that it has to take in hot weather I want something that won't give up the ghost.

I bought a $20,000 motorcycle. Why would I skimp on $30 worth of oil.

Harley doesn't want you to use anything but Harley.

You don't need to get Diesel oil.

 

guess we're lucky down here

20w60 diesel available EVERYWHERE

rated gasoline and diesel

loaded up with zinc etc

why bother with a skimpy little car oil ???

i'd use 20w50 auto oil " at a pinch " and change it out pretty quick

 

I was able to find Mobil 1 15W-50 in two local stores and it looks like it will be my choice as it is a synthetic and CF rated (diesel). My problem is that I did not want to have to drive the 60 mile round trip to my closest Harley dealer every time I needed oil. My consideration was more about getting adequate protection from readily available products - not cost. I also did not want to foolishly waste my cash. With all the good information that I have researched on this forum, some local shopping, and some help from you and others, I have been able to make an informed choice.
Thank you all!