15w50 vs 20w50 whats the difference?
Supporter
Joined: Mar 2011
Posts: 587
Likes: 1
From: Ga.
Since most wear in an engine occurs in the first few seconds of operation after a cold start, I would think better flow when cold would be an asset. The protection of engines with "looser tolerances" is more than adequate with both oils' ability to protect like a 50-wt. when hot. You will not incur more wear using a 15w50 over a 20w50, all other factors being equal. If anything the 15w50 may actually provide better overall lubrication because it has more friction modifiers in the formula.
Much of the oil recommendation is to allow the mfr. to display a higher gas-mileage rating, not only to spur sales but to better satisfy the government's CAFE requirements.
Much ado is made over oil brands and types, and the truth is that any synthetic oil near HD's viscosity spec is fine. That would include 14w50, 20w50, 20w60, etc. I know people with high-mileage bikes who use M1 15w50, as well as a few who use the much-maligned Syn3. It's all good, but IMO the biggest factor for choosing the right oil is cost. Ask an oil engineer who is willing to give you a non-corporate opinion.
I might as well tell this story again for the 10th time: A friend and very-qualified tech performed a BB upgrade on his and a friend's bikes, both 2000 FLH's. He had used M1 15w50 in his bike and the other guy 20w50 Amsoil MC oil. When they disassembled the pertinent componets of both bikes there was no visible or measurable wear on cylinders, pistons, or valve-train components. The M1 bike had 60k and the Amsoil 50k on the clock.
Much of the oil recommendation is to allow the mfr. to display a higher gas-mileage rating, not only to spur sales but to better satisfy the government's CAFE requirements.
Much ado is made over oil brands and types, and the truth is that any synthetic oil near HD's viscosity spec is fine. That would include 14w50, 20w50, 20w60, etc. I know people with high-mileage bikes who use M1 15w50, as well as a few who use the much-maligned Syn3. It's all good, but IMO the biggest factor for choosing the right oil is cost. Ask an oil engineer who is willing to give you a non-corporate opinion.
I might as well tell this story again for the 10th time: A friend and very-qualified tech performed a BB upgrade on his and a friend's bikes, both 2000 FLH's. He had used M1 15w50 in his bike and the other guy 20w50 Amsoil MC oil. When they disassembled the pertinent componets of both bikes there was no visible or measurable wear on cylinders, pistons, or valve-train components. The M1 bike had 60k and the Amsoil 50k on the clock.
I also agree about the oil manufacturers, the reason I said, why would I trust any oil company. I mean I know that some labeling is done to increase price, on a lot of items.
I see that while I was typing, you basically replied what I was typing, so once again, I really believe we are on the same page, just different wording.
Last edited by Copyless; Mar 26, 2011 at 08:15 PM.
Road Captain
Joined: Jun 2009
Posts: 659
Likes: 2
From: Central Ohio
I am with iclick and bigdumbnoitall00. Mobil 1 15w50 in the motor and primary. Gallon jug from Walmart covers that. Bel Ray Clutch in the tranny. The 15w50 in the tranny is not a good idea. Change fluids and filter twice a year after running long and hard. Fluids come out with minimal break down and components run cooler and quiter. 
Road Warrior
Joined: Jan 2006
Posts: 1,282
Likes: 115
From: British Columbia
Thanks guys for the info, I will go back to the M1 15/50. I used to use it for years till someone scared me off of it. I have amsoil in my bike right now and I find the motor is quite a bit noisier with it, wil be going back to the M1 asap.
Extreme HDF Member
Joined: Sep 2005
Posts: 11,615
Likes: 50
From: Baton Rouge, LA
Oddly, no--but I recommend it to friends frequently. I have a friend who is a distributor for a competitive brand and I get my oil, grease, etc. at wholesale prices by the case or 5-gal. pail--plus he delivers it to my door. All of the name-brand products are good and if this source faded away M1 15w50 would certainly be on my short list. Again, I think the biggest difference between oils is price, and that is dictated by what the manufacturer thinks he can get for it, driven by whatever hype he can throw at the customer. Believe me, there is plenty of hype in this industry, much of it coming from over-zealous customers who think their oil is some sort of panacea. The more I learn about oil the more I know there is no oil that is superior to others in all categories.
Last edited by iclick; Mar 26, 2011 at 09:48 PM.
Extreme HDF Member
Joined: Sep 2005
Posts: 11,615
Likes: 50
From: Baton Rouge, LA
Indeed, I would avoid the 15w50 in the primary, but although the 20w50 is technically correct I think it is severe overkill. You don't need a high-tech synthetic in the primary. I use a cheap 20w50 fossil oil and it works well. My old Evo ran $1/qt. no-name 10w40 fossil motor oil from Wal-Mart for >100k miles and I never had any problems in the primary. The primary oil only needs to lubricate the chain and a few roller bearings, plus keep the clutch disks cool. You could probably use peanut oil in the primary, but I'll let someone else experiment with that. Some guy ran his new RK a few hundred miles before discovering the factory or dealer forgot to insert the primary oil, so it doesn't take much lubricity to keep things working in there. OTOH, I wouldn't suggest that!
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