Royal Purple question

[mjpxs11sh]

someone had a post i couldnt find again, about putting Royal Purple Max Gear-Oil 75W140 in the middle gear box/final drive. i researched and found they also make 75W90. my question is about the weights. why 75W140 instead of 75W90? the latter more closely matches the OEM spec 80W90. thats what i put in mine and not happy with the whine. will 100% Synthetic quiet it down? thanx

[jetmechmarty]

will 100% Synthetic quiet it down?

Maybe a little. Maybe not. I run Mobil 1 75W90 in mine.

[TADracer]

I wonder also what the advantage of 75/140 would be. Not much heat is developed in the middle/final drives so that is probably the reason that the spec'd. lubricant is so close in viscosity number. I am thinking that unless the units really heat up the viscosity will not change toward the lower number much and in effect you are using oil that might be way too thick.

[3Phase]

... my question is about the weights. why 75W140 instead of 75W90? the latter more closely matches the OEM spec 80W90. thats what i put in mine and not happy with the whine. will 100% Synthetic quiet it down? thanx

It depends on what's whining and why. The XS11 does have some whine and gear noise but it's usually not too bad. A lot of noise comes from the HyVo chain on the crankshaft/primary shaft and from the straight-cut gears in the transmission and the output gears to the middle drive. If you add fresh or thicker engine oil and that cuts the whine then it's probably not the middle or final drive that you're hearing.


Check the driveshaft splines and the splines in the middle drive yoke and final drive coupler to see if they're running dry and need some grease or if they're worn out and hammered. They'll make noise if they run dry or get damaged.


If the whine is from the middle drive you can try the 75W-140. The middle drive temperature is almost the same temperature as the rest of the engine and transmission so a 75W-140 should work really well. If that doesn't do it then get another middle drive that doesn't whine or at least doesn't whine as much as the one you have.


The final drive itself shouldn't whine too much or get too hot unless there is something wrong with it. Normally a 75W-90 is just fine but you can use 75W-140 if you want to and you won't have to buy and keep two different grades of gear oil.

If it really is the final drive itself that's whining then just get another final drive. Stock XS11 final drives are cheap so there's no real reason to mess around with putting thicker oil in a worn out final drive.


You could also try out a 750/850 final drive and see if you like it.

[crazy steve]

my question is about the weights. why 75W140 instead of 75W90? the latter more closely matches the OEM spec 80W90. thats what i put in mine and not happy with the whine...

There's still a misconception out there about how multi-grade lubricants work... The number with the 'W' after it is the actual viscosity, so a 20W50 is 20 weight, and 75W140 is 75 weight. They don't 'thicken' to the higher viscosity when warm, contrary to what you'll read some places. Don't believe me (or them), check it yourself with a viscometer; get some 10W40 and straight 40W oil, check them cold, then heat them and re-check. The straight-weight oil will still be thicker, and both will be thinner heated than when cold...

How multi-grades work is the thinner lubricant is bolstered with additives so it will carry the same load as a heavier lubricant, designated by the second number. So a 75W gear oil will always be 75W, the second number tells you the equivilent straight-grade load it will carry. So you can use either 75W90 or 75W140 gear oil, the only difference being the 75W140 is capable of carrying higher loads like a 140W and is the 'better' oil.

Why the difference? The bigger 'spread' between actual viscosity and 'rated' viscosity means they have to add more/better additives, making it more expensive to produce. The downside to multi-grade oils is as they are exposed to heat/'wear'/contaminates those additive will start to break down, leading to a reduction in load-carrying capabilities, so your 20W50 will slowly degrade into a 20W30 or even just 20W.

[XSive Okie]

Steve is 100% correct. 10W40 is 10 weight oil that has an additive package that allows it to protect like a 40 weight. In essence, the thinner oil is more easily pumped through the mechanism (engine, trans, etc.) allowing increased fuel mileage, while giving better protection. That is why automotive manufacturers have pretty much all switched to 5W20 or even 0W20 oil.

[mjpxs11sh]

75W140 gear oil

thanx all! Steve, now i see why ur a Guru. my understanding is the SAE 75W= viscosity when cold and the 140 is the viscosity at normal operating temp. is that correct mr. Guru?

[crazy steve]

... In essence, the thinner oil is more easily pumped through the mechanism (engine, trans, etc.) allowing increased fuel mileage, while giving better protection..

Absolutely correct. But mileage wasn't the original reason multigrades were developed; they discovered that something like 90% of most engine wear occurs during start-up because the oil has drained off/out of the places it's supposed to protect. By using a lower viscosity oil, the oil 'pumps up' faster, reducing that 'start up' wear.

There is a caveat attached to multigrade oils; the motor needs to be designed for them. Switching from a 20W40 to a 10W40 really shouldn't be done if the motor was designed for 20W. Pressurized bearings will generally tolerate a lower viscosity as long as you don't go too low, but 'rubbing' sufaces like the pistons/rings/cylinders or cams/lifter don't like the lower viscosity oil as it leaves a thinner film. Go too thin and you'll wipe out the cylinders.

As far as gear oils (the original question), there's basically no difference between 75W90 and 80W90, and you could use the 75W140 with no issues...

[mjpxs11sh]

Great 411! i know when i tried to start my XS11 with 20W50 engine oil in Chicago January, it barely turned over. i had to jump it with my cars alt amps to get er goin. that was after she had been alone for over 10yrs. have a good one all!

[crazy steve]

thanx all! Steve, now i see why ur a Guru. my understanding is the SAE 75W= viscosity when cold and the 140 is the viscosity at normal operating temp. is that correct mr. Guru?

Nope...

Viscosity does change as temp goes up; it goes down. Unless you overheat it and boil the lighter oil components out, then it will thicken but you've killed whatever you were trying to lube.

The 140 number (or whatever number comes after the 'W') is the 'equivilent to' rating. In other words, a 75W140 is a 75 weight oil that can perform the same lubricating and load carrying as a 140W.

Now, there are some synthetics out there that retain viscosity better when heated than conventional oils, so from that standpoint you can possibly say they 'thicken'. But they're really only not thinning out as much.

[Rickrider]

oil viscosity or gear oil viscosity

As I recall from working with my Dad in the oil fuel distribution business many years ago the "W" in an oil or gear oil rating means "Winter" and is the viscosity of the oil at zero deg C. The following number is the rating at 100 Deg C. So 75W140 is 75 viscosity gear oil at 0 deg C and 140 deg viscosity at 100 deg C. And note that oil viscosity and gear oil viscosity are not the same. Again digging into the past, I believe that for example 80 viscosity gear oil is about the same as 40 viscosity engine oil.

My .02 cents.

[mjpxs11sh]

great input Rick. right on the money. i dont think everyone knows that SAE gear oil is rated differently than motor oil. for everyone in the USA, 0 deg c=32 deg farhenheit and 100 deg c= 210 deg f or normal operating temp.

[jwhughes3]

wikipedia motorcycle oils

I wanted to copy and post the info from Wikipedia about motorcycle oils and why its important for motorcycles to use motorcycle specific oils designed for use in the engine AND transmission - (note where it states how the tranny cogs shear the oil - I bet many of the XS11 2nd gear issues relate to use of regular oils instead of MC oils)

Motorcycle Oils are a range of lubricants, including engine oils, which are specifically developed and marketed for use in the internal combustion engines and transmissions of motorcycles and may also be recommended for use in vehicles utilizing drive-trains similar to those of motorcycles, such as quad-bikes.

The vast majority of modern motorcycles use the same oil to lubricate the engine, transmission, and (with the exception of bikes with dry clutches, such as Ducatis and some BMWs) the clutch. Normal, "car-derived" motor oils are designed just for engines, but were historically suitable in motorcycles. However, some of the latest American Petroleum Institute, or API specifications are completely unsuitable for motorcycles with wet clutches. Representative organisations of motorcycle manufactures, particularly Japanese Automotive Standards Organization, or JASO, work with lubricants manufacturers to create "motorcycle-specific" standards for oils, and the relevant oil companies then develop and test oils which are specifically made for motorcycles and in return, they have two different products with the same chemical content.

Transmission lubrication

Motorcycle transmissions, just like all gear-based automotive transmissions can quickly degrade a multi-viscosity, or multi-grade engine oil. Conventional car and truck transmission oils have specific EP, and other specialised anti-wear additives, but these EP additives are not suitable for the combined application of lubricating the engine and transmission with the same oil, as is the norm in motorcycles

Multi-viscosity oils contain viscosity improver chemicals known as VIs that keep the oil from becoming too thin at high temperatures. The VIs are large chemicals that tend to shear between the cogs of a motorcycle transmission. That can have the effect of reducing a 10W-40 oil to a 10W-30 in a relatively short number of miles.

One solution to shearing is to use single weight oils, which do not have VIs and aren't susceptible to degradation in the transmission. However, single weight oils do not flow well in cold conditions, reducing overall lubrication until the oil has warmed up. An alternative is to use a synthetic oil. Synthetic oil are designed to have good cold-flow properties yet maintain high viscosity with fewer VIs.

Clutch lubrication

Energy Conserving (EC) oil can cause wet clutches to slip
Many motorcycles have a wet clutch, where the clutch plates are immersed in oil. Some oils make the friction plates in the clutch slippery so that the clutch doesn't engage properly when shifting gears, or the clutch slips when the engine exceeds a certain torque. Some oils contain friction reducing chemicals. One element of the JASO-MA standard is a friction test designed to determine suitability for wet clutch usage. An oil that meets JASO-MA is considered appropriate for wet clutch operations. Oils marketed as motorcycle-specific will carry the JASO-MA label. A properly specified motorcycle oil will still allow for the appropriate lubrication and cooling of a motorcycle clutch, whilst maintaining 100% of the drive to be transmitted by the clutch, even under arduous operating conditions.

John

[BA80]

I've been using Royal Purple 75w140 in my middle and final drives since I got the bike.

The fully synthetic 75w140 is what is used in the most picky of automotive differentials ( late model Ford F series trucks).

[jwhughes3]

I heard good things about RP gear oil

From 3Phase - I am thinking of using that very 75W140 synthetic in my middle and final drives as well... In my truck I have always used Mobil1 - but am open to new choices.

John