Motor oil for tropical application - Harley Forum

admin · #1 05-25-2007, 01:46 PM

I live on a tropical island in the South Pacific, I've decided to use straight 50W from HD as motor oil, istead of 20-50W. Anybody out there know if I'm correct doing this?

Posted by: Borafatboy on Dec 6, 06 9:07:51 pm

admin · #2 05-25-2007, 01:46 PM

Don't do it.

Period, end of discussion.

Use a synthetic though, high heat is one of the real reasons to use it in the engine, mainly due to increased oxidation resistance.

The viscocities of both are about the same at operating temp. It's startup that will kill your engine.

What you should realize is that there are 3 temps oil is measured at.

Pour point given in degrees

Viscocity at 40C given in CentiStokes

Viscocity at 100C in CSt

An example 20W50 and a 50 show the folowing

20W50 pour point -17F 40C visc 162 100C visc 18.1

50 pour point -15F 40C visc 195 100C visc 18

From this you can see that there is reduced flow at lower temps. So how much lube is flowing at start up?

Posted by: BluesFan on Dec 7, 06 1:14:36 pm

Syntheticoilexpert · #3 09-13-2007, 07:01 PM

BoraFatBoy, BluesFan is correct, don't do it. Straight 50W is too heavy.

Older Harley's, way older used a straight 60 weight, but new bikes, stay with the 20W-50 and go synthetic, way cooler in hot temps, plus better engine protection.

indcoltz · #4 07-14-2009, 01:39 PM

I have 08 Ultra Screaming Eagle 110, I live in Southern Indiana where the summer temps can get in the high 90s. I have started using Amsoil Syn 60w in my bike. Used it to go to the UP in Michigan the first of July, morning temps up there dropped to the low 50s. I had no problems. Coming home the temps jumped to the high 90s. The bike never ran cooler before and the engine was never as quiet, even in the Upper Michigan. So you guys think I shouldn't be using a straight Syn 60w? Why?

milindh · #5 07-14-2009, 02:23 PM

Hey Indcoltz

I'll jump in here and give my take on why multi-viscosity oils are better.

When an engine is cold all the moving parts are kinda shrunk down cuz metal and most things do that when they are cold. Round surfaces like cylinder walls and outer bearing sleeves (like wrist pin bushings) get tighter against their pistons and inner surfaces (like wrist pins). That means less clearance for oil to get into upon start up.

Now, multiviscosity oils are actually thinner upon start up when cold and the heat generated by the engine as it warms up makes the oil get thicker as it is heated (that is until the oil gets so hot that is starts to break down and get thinner again).

20w 50w is 20w when cold and 50w as it heats up.

Straight 50w (or 60w in your case Indcoltz) is thicker upon startup and has a harder time getting into those tight spots when the engine is cold. After the engine is warmed up it is still 50w (or 60w). Also keep in mind in Indiana it might be 50 degrees in the morning and 95 deg in the late afternoon.

In the Bad Old Days engines were built and run with looser fitting parts and tolerances but today's engines are built to much tighter tolerances and are actually designed to run on multiviscosity oils from the get go. They didn't even have multivis oil back then. It is this theoretical oil starving of the bearing surfaces when the engine is cold that is said to cause premature surface wear with the straight weight oils.

Ok, so there's the theory as I understand it. How much actual extra wear you are causing by running straight 60w is hard to tell but I'd bet it's significant. I run Mobil 1 15w50w synthetic in my pumped up FXR and it gets way hotter out here in Cali than in Indiana. Over 100 today and go inland five miles and it'll be 105.

If your bike is still on the warranty I wouldn't tell the dealer you have been doing this. They'd probably void your warranty.

Good Luck dude

indcoltz · #6 07-14-2009, 07:08 PM

Don't take me wrong sometimes I come across as a smartass and don't mean too. We have already had several days in June with a heat index of over 105 degrees. I work for the dealer here so I'm not worried about any warranty issues. Yes I know the tolerances are much tighter now than back 25 years ago when I had only been riding a couple of years. But correct me if I'm wrong I have been told that Synthetic Oils leave a longer lasting film of oil. When the engine hits it's running temp of around 230 degrees what would be the difference of a 20w50 getting into the small areas than a straight 50 or 60 in synthetic oil? I know and understand what you are saying about cold starts. I'm not one that races the engine or as I call them a throttle jockey while the engine is warming, I rarely even start out until the headers are close to being hot. I'm not trying to justify why I put the 60w synthetic oil in I just appreciate the input to open my mind to other theories. Again thanks and please don't think I'm trying to be a smartass just want a better understanding of all the bull**** there is on oil. I wonder why Harley recomends 60w oil in the engine under 60 degree weather and above?

milindh · #7 07-14-2009, 10:05 PM

Indcoltz

You don't come off as a smartass at all. The only people that could definitively settle this would be the Harley engineers that have surely tested this thoroughly. Working at a dealer might give you access to some of those guys. I'd like to hear what those guys have to say.

unclepsycho · #8 07-14-2009, 10:40 PM

Oh.... I thought the heading said...''motor oil for TOPICAL application''

I was gonna change sun tan lotion... but now....

(yeah, I am a smart-ass

and my wife says I am good at it.)

It got to 105 here today, an hour and a half north of the golden gate bridge....

unclepsycho · #9 07-14-2009, 10:47 PM

On the serious side..... Multi weight is thinner when cold, then gets thicher when heated.... I have thought that's what this means ever since i can remember..... so why do I start the engine and let it warm up before I change the oil? I have always done it that way.... but now... it sounds like it should be changed when cold???

the laws of physics are messin with me here..

I work with epoxy at times... we got some low viscosity epoxy to pump in concrete walls to seal the cracks, after we applied a 'higher' viscosity epoxy on the outer part of the crack to hold the low stuff in there....
the low viscosity epoxy is runny
the high viscosity is more like paste.

is this anology even close ? or am I comparing apples to bicycles....

Whopper · #10 07-15-2009, 08:58 AM

I was taught that multiweight oil's viscosity thins at a different rate than straight grade oil. A 20W50 oil would have the viscosity of a straight 20W when cold but would have the same viscosity as 50W when hot. If I remember correctly, they measure the viscosity at 32F and 212F. A straight 50W would be thicker than 20W50 at 32F but they would have the same viscosity at 212F.