why do motorcycle oils never fall below 10W ?

[kmrcstintn]

I usually run 10w-40 in my common sump bikes...tried 15w-50 in a yamaha v-star 650 (lost the feel for gear engagement); tried 20w-50 in a Suzuki gz250 (engine worked very hard and was very, very hot during idling in traffic); tried a 10w-40 & 20w-50 blend in my honda shadow 750 (very hard shifting engagement); if I want to thicken oil during warm temps I add some 15w-40...40wt is what they like so that's what they get! same thing with the scoot...10w-40 & 15w-40 blend

 

[barryh]

For those that do ride during the winter or as I do commute to work, one of the issues is the oil just isn't going to get up to full operation temperature on an air cooled engine. To me that is a good reason for using a 5W40 or even a 0W40 oil. It's all very well saying 10W40 is still pumpable down to some ungodly temperature but I like the starter to spin the engine as fast as possible and I'm interested in the viscosity being thinner than a 10W40 would be during the ride when the oil is not going to get anywhere near 100 Deg C. I have a dry clutch and separate gearbox oil so the shearing concerns don't apply.

 

[Mik]

Originally Posted By: Panzerman
Polaris came out with 0w40 motor oil for thier first four stroke ATVs in the mid 90s and I remember thinking that was crazy. Now you see 0w oils everywhere.


Polaris ATVs do not have a wet clutch and constant-mesh gearbox, however (they use CVTs). A VERY important difference with shared sump design motorcycles.

 

[Analyzer]

Originally Posted By: Mik
Originally Posted By: Panzerman
Polaris came out with 0w40 motor oil for thier first four stroke ATVs in the mid 90s and I remember thinking that was crazy. Now you see 0w oils everywhere.


Polaris ATVs do not have a wet clutch and constant-mesh gearbox, however (they use CVTs). A VERY important difference with shared sump design motorcycles.


Very true indeed. Beyond that Polaris now specs either a 5W50 or 10W50 viscosity oil for motor (plus their AGL fluid for the transmission and rear differential).

 

[BrocLuno]

I think the OP was referring to OEM recommended lubricants - MFG branded oils... They do not want engine failures in warranty. Better safe than sorry

 

[bonjo]

Add silcolene to the 5w-xx list

If by expanding plastic in the oil you are referring to "polymer", I understand this is used for mineral & group III oil and the higher the VI, the more is needed and they sheer!

I also understand (and hope) full synthetic (Grp IV & V) do not need these additives)

you can experiment with 5w-xx if you live in cool / cold climate. I ride all year and sometimes in temperatures below 5, still find 10w50 excellent. I think the key is to use a fully synthetic oil

 

[SuperSalad]

Originally Posted By: bonjo
Add silcolene to the 5w-xx list

If by expanding plastic in the oil you are referring to "polymer", I understand this is used for mineral & group III oil and the higher the VI, the more is needed and they sheer!

I also understand (and hope) full synthetic (Grp IV & V) do not need these additives)

you can experiment with 5w-xx if you live in cool / cold climate. I ride all year and sometimes in temperatures below 5, still find 10w50 excellent. I think the key is to use a fully synthetic oil

Full synthetics also commonly use viscosity modifying polymers in their formulas. They are pretty universally utilized except for monograde oils and the occasional exception which I'm sure exists.

 

[bonjo]

didn't know that.

thanks

 

[donnyj08]

MV Agusta specs 5w40 Eni Agip for their bikes.