kinda thought so. Lol. So essentially you could use 5 qts of synthetic oil (hypothetically of course), and everything would be fine. Just never really gave it much thought. Thanks!

 

That is absolutely correct. I did a comparison a few years ago. You actually save money with syn. Just engine oil/filter for 15K miles = dino oil cost $232.45, syn oil cost $178.41 a saving of $54.04. Plus, time saved on less syn changes - AND - less crap going into landfills.

If you want to change back and forth - go for it, you will not destroy your engine. Just make sure you change the oil at the recommended intervals for each.

 

Red Line Motorcycle 20W-50 @ Bezos World for $14.97 per quart in 12 per case. Best price I found, for those that use it.

I didn't check on Mobil 1 V-Twin 20W-50 prices - I cruise, so do lots of stops and starts in high temp traffic and only need to change once a year (<5,000 miles / year), so I use the expensive stuff.

 

 

My 99 EVO does not like synthetic. I tried Mobil 1 and within a couple of hundred miles the base gaskets started weeping oil. Switched back to Castrol 20-50 non synthetic, and they stopped leaking. I only have 65,000 miles on it, but have had no problems and it uses so little oil between changes that I never have to add any. Synthetic probably works well in the newer engines, but the older ones seem to work better with non synthetic. At least mine does. Of course, the EVO is just an improved Shovel Head. Not much difference except for the alloy cylinders.

Heck, I use to use 90wt. gear lube in my 42 Flat head. Back in 1955. It was 50 miles from our little town to the nearest Harley shop. It seem to run fine on the gear lube. But "45" Flat Heads were pretty bullet proof. I was 14 and treated that bike terrible, but it just kept running. Wish I still had it. It was no speed demon, but a hoot to ride. To this day a foot clutch and hand shift seem normal to me.

 

I know this gets kicked around a lot, I just visited a different HD site where I read it suggested to run 75/90 in the Primary.

On a Harley Davidson you have three different oil requirements, and I get creative just for the joy of choosing the best for each:
1. Engine oil.- Your do not need motorcycle specific oil here (with special additives to avoid clutch slippage, or gearbox specific additives, like antifoam), because this oil is not shared with the cavity where the clutch is, or the gearbox. Therefore, I use Liquimoly 20W60 Racing, Group IV PAO base oil
2. Gearbox.- Here, you need antifoam additives, so I use Liquimoly 75W90, gearbox specific
3. Primary (where the clutch is).- Here you YOU DO NEED a motorcycle specific oil, so I use FOR THIS CAVITY ONLY Liquimoly HD Synth 20W50 synthetic Group IV PAO base oil. Do not use gearbox oil here, because it will cause the clutch to slip.
Oil is the most controversial topic you will find anywhere, have fun!! Hope this helps.

 

I have a 2017 M8 Road King Special, my first and only Harley. Older Harleys may have different preferences.

 

did ding ding we have a winner !!! for the longest lubrication description name ever !! with a name like that how could one possibly go wrong !!!

my choice is at the complete opposite end of the pendulum for name length with only 4 characters... SYN3

 

What about GT1?