Syn3/Sunoco is ok at best. there are much better full synthetic oils out there...
Not sure why you want to go backwards with the "dino" oil, but yes you can just drain the old and put the new in.

 

While you're at it, drain that stuff out of your tranny and put some tranny fluid in there. You'll like the difference.

 

Worst oil I ever used. Breaks down way to easy. Go with a PURE synthetic such as Amsoil, Mobil 1, or ANYTHING even Dino oil just get away from Syn 3. I think HD put Syn 3 on the market just to casue motor problems. Everyone I know that ran the crap and got over 60ish thousand had motor problems. People running TRUE synthetic have less problems from what I have seen.

 

The additive packages on motorcycle syn and dino are about the same. They are mandated by the EPA and manufacturers of the oil. Harley would not put out an oil that was harmful to the engine. I have 107K on my 1988 FLHS using dino exclusively. If I could afford a new bike I might look further into a synthetic. The only advantage a synthetic really has is longer time between changes. If you are changing at 2500-3000 miles then syn is a bit of a waste of money. If you change at a lot longer distance as Harley now recommends then I would use dino but I have an old habit from my Shovel Head days of 2500 miles and do well with dino. Use the internet and do some research.

 

Using Synthetic does NOT increase your oil change intervals. It is better at handling slightly high temperatures without breaking down.

At 14K I put cams and a 103 kit on my 2010 Heritage Softail. I have had a Harley Oil Cooler since 1,500 miles. Other than at 500 miles and 1,500 miles, I have changed the oil and the oil filter every 2K but have alternated between synthetic and dino. I've built a lot of engines in my day and with this kind of oil change frequency the inside of the engine should have been spotless . . . and to a large extent it was (Crankcase, Cam Chest, etc.). BUT, the Rocker Boxes (where the Rocker Arms and Valve Springs, etc. live) had a film of olefin (wax) that indicated to me that oil has gotten hot enough in that location to begin breaking down. Having read a History of this engine, Harley restricted the oil flow to the Heads/Rocker Boxes as part of a developmental solution on the Twinkie engines to manage a temperature control issue they were having. Fromm what I saw, the solution is very hard on the oil that does get into the Rocker Boxes. Ergo, the engine will now get synthetic oil at every oil change.

 

Been using Mobile synthetic 20/50 for a long time and now use Mobile v-twin synthetic at a higher price. Like others have said change your transmission to a thicker multi weight synthetic and enjoy the difference.

 

Actually most syn lubes are recommended to be changed at every 7,500 miles.
This benefit is not widely promoted by the major oil producers most likely because they want you to pay a premium for their synthetic oils every 3000 miles just like their regular oils.

 

The whole idea behind synthetic oil is that it handles higher temperatures better then conventional oil. It doesn't break down as easily under pressure, synthetic has better lubricity properties (hangs to internal parts much longer so during start ups there is much better "filming" of the parts), synthetic's usually do a better job of suspending foreign material so it filters better. Added up, this is the reason oil change intervals are lengthened for synthetic's, but the filters are suggested to be changed out at the same time as conventional oils. Change the filter @ 2-2.5 add synthetic to top it off and then change both oil and filter @ 5K. My opinion only.

 

If that's true, then why is SYN3 labeled as "full synthetic" and why does Harley also sell a synthetic blend?

 

SYN 3 AND MOST OTHER HARLEY LUBES ARE MADE BY CITGO

Use what makes you happy...just know that when you buy H-D oil and Citgo (Petro Express), you are helping support Chavez (he owns Citgo) and his profit goes to any cause to harm the USA.

You would think that an American icon like Harley Davidson would drop Citgo like a warm turd!!!