The Yamaha Road Star Warrior Forum

I'm plannining running Mobile 1 synthetic 10w-40w for mororcycles in my Warrior and it's comatible with wet clutches. But I see that some on this 4M are running Amsoil synthetic for V-twins 20w-50w. My Yami dealer is also recomending Amsoil 20w-50w. But the manual calls for 20w-40w so wouldn't it make more sense to run the 10w-40w. I'm conflicted to wich one. Appriciate any advive

You can use either but 50W increases the oil pressure & it wont protect any better than the 40W.The important number is the 2nd one as the 1st number is for when the oil is cold.Basically all Jap bike motors call for 10W40.Amsoil is rated best by an independent lab & you can probably get it cheaper than Mobil1 for bikes.You can use oil for cars as long as it doesn't have the energy conserving star on the label which you wont find on any 10W40 or 15W50 that I know of.Walmart has both of those weights in Mobil 1 for $22.88 for a 5 qt jug.I use the 10W40 Mobil 1 in both of my bikes & it works fine.Any full synthetic brand in those 2 weights you can't go wrong with.I change it once a year regardless of miles but I rarely put over 5000 miles on either bike in a year.The guys here use all 3 weights & different brands so it's your choice.

My thinking is the heavier 50w would rob power and gas milege, where 40w seems plenty heavy even for extreme conditions. but I'm no expert on oils

You'll find that a lot of members here also use Mobil 1 V-Twin Full Synthetic oil...This is what I run and have had NO problems...It seems to smooth out the shifting and quiet it down a bit, as well...

My friend who owns a Victory Hammer just tried Amsoil and he switched back to the Mobil 1 V-Twin because he said the bike just didn't seem to run as well with the Amsoil.

You can get the Mobil 1 V-Twin at most auto parts stores, like AutoZone for around $8 to $9.00 a quart.

Mark aka Mad Man

If using Amsoil or Mobil 1, 10w-40 is the correct replacement for the Yamalube 20w-40.  Many prefer 20w-50, it will not hurt anything, but as correctly described above, the difference will be the greater resistance to flow using a little more power to run the oil pump instead of the rear tire.

Oil Geek stuff:

Viscosity is ordinarily expressed in terms of the time required for a standard quantity of the fluid at a certain temperature to flow through a standard orifice. The higher the value, the more viscous the fluid. Since viscosity varies inversely with temperature, its value is meaningless unless accompanied by the temperature at which it is determined. With petroleum oils, viscosity is now commonly reported in centistokes (cSt), measured at either 40°C or 100 °C (ASTM Method D445 - Kinematic Viscosity).

The numbers on the oil bottle are converted from cSt to an SAE number.  The SAE numbers are the 20 and the 50.

Here is a description of how multiviscosity oils work:

At cold temperatures, the polymers [viscosity improving additives] are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up, the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C, the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

I'll stop here unless someone has insomnia.

If you want more testing and definitions and technical info, see this Link 

I'll throw in my .02.

I always used Mobil 1 v-twin 20w-50 and on a hot summer day in traffic, oil pressure would get lower than I liked....even with my idle set correctly, it would drop to 12-15psi at idle.  That's how I could tell the bike was getting hot.  You really notice it when you have an oil pressure gauge. 

Just my .02...I wouldn't run a lighter oil in a hot climate or if you get stuck in traffic very often.

Another vote for Mobile 1 V Twin 20-50 synthetic . Best oil I've used.

Slickest shifting opil I have ever used is Motul full syn - I buy the Mobil1 a wallyworld because the price is right and its a good oil...the tranny is the only place I have felt a difference in performance with oil.

I run Mobil-1 V-Twin, and find it smoother shifting and smoother running, especially when engine is hot.

Local Walmarts are no longer selling the Mobil1, are yours still selling it?

Tomasa:

Local Walmarts are no longer selling the Mobil1, are yours still selling it?

 +1

messx03:

Another vote for Mobile 1 V Twin 20-50 synthetic . Best oil I've used.

I can only find Mobil ! Synthetic 10/40 in a high milage oil. Is anyone running this? I didn"t know if it had an additive I should't use. I did a search but can't find any info on this. I want to change to synthetic 10/40 but didn't want to pay the 8-9 dollars a quart for a motorcycle specific oil. Thanks for any replies. 

You can normally find the Mobil 1 at Autozone.  After using it, I personally wouldn't got back to Yami lube due to the reasons listed above.  Don't think about it being $8-9/qt, think about it the same way you would a tire, head light bulb, or any other part that wears out on a regular basis.  How many of us will spend big $$$ on mods, but go cheap the really important stuff to protect our investment?  The difference in price is about a tank of gas if that puts it into prespective.

 Would synth blends be a no-no ?