There's a lot of myths about oils that are or not suitable for our machines, and most of them have absolutely no factual basis.
"Don't use an energy Conserving oil or your clutch will slip."
"You must use a JASO MA rated oil in your engine or you'll cause premature failure and wear."
The myth about automotive oils making your clutch slip started when the Energy Conserving (EC) standard came into being. EC oils have much lower levels of zinc and phosphorous, because these additives can damage a catalytic converter. And the word moly automatically makes people think that the moly additive will cause buildup on the plates which will lead to slippage. But the truth is there is nothing wrong with oils that contain moly, and in fact many motorcycle-specific oils contain moly. I have yet to see any evidence to show that any so-called "friction-modified" (Energy Conserving, or EC) oil will cause any problems. In fact, all engine oils have friction modifiers of some sort in them. The Energy Conserving designation (EC) was devised to denote oils that met new emissions standards requiring lower levels of phosphorous. The EC standard is about emissions, not friction.
Since the standard requires a reduction in useful additives such as phosphorous and zinc, the manufacturers had to come up with replacements. One of the additives that the oil engineers can use to bring the lubrication properties back to the level that it was with the higher levels of phosphorus is molybdenum (moly).
The problem with the belief that the moly additive will make clutches slip is that oil companies don't use the form of moly that would cause this problem, Molybdenum Disulfide MoS2. That type of moly is typically used for the formulation of industrial gear lubes, chain lubes, and greases, not engine or transmission oils.
Engine oil formulators use Molybdenum DialkyldiThioCarbamate. This formulation of moly has been proven in both lab testing and actual use to not cause clutch problems at any level you are ever going to find in an oil bottle.
The funny thing is, many people will start beating the "moto-specific-oil" drum, and try to tell you that if you don't use motorcycle oil, your clutch will slip. But in fact, many JASO MA rated (certified for use in a wet-clutch environment) moto-specific oils contain levels of moly that are much higher than any EC-rated automotive oil. So if it's bad in an automotive oil, why then is it perfectly acceptable in a motorcycle oil?
Even the JASO MA rating is itself a scam in my opinion. All it means is that an oil has been submitted for certification as to it's ability to operate in a wet clutch environment. That does not, however, mean that a non- JASO MA oil will not perform equally well in the same wet-clutch environment. Many oils are simply not submitted for this certification, beca7use the manufacturers are not specifically targeting the motorcycle market, so they do not wish to invest the time and money required to obtain that certification. And in fact, there are more than a few motorcycle specific oils on the market that do not have the JASO MA certification.
Most any oil will be acceptable in your tranny, as long as it is changed at reasonable intervals. The problem is, what would be considered a reasonable interval for any other engine is not a reasonable interval for our bikes. The real enemy of oil in our trannies is in contamination from the clutch, and viscosity-shear from the gear teeth. The only solution for those problems is frequent oil changes. In most cases, choosing an oil that your budget allows you to change frequently is better than choosing a much more expensive oil that you aren't willing to change as often because of the high cost.
So called "diesel" oils are nothing more than automotive oils with a more robust additive package, especially higher detergent levels. Some of the best performing oils that you can find for our trannies are diesel oils such as Delo and Rotella T. And some of those high-dollar "boutique" moto-specific oils will shear out of viscosity faster than a standard off-the-shelf auto oil. Most oils will shear out of viscosity in our transmissions, under race conditions, in as little as 4 hours. If that doesn't convince you of the need for frequent changes, then nothing will.
I Use ATF type F in my two-stroke trannies. It's an excellent choice for a wet clutch environment, it has better thermal stability and shear resistance than most engine oils. It's also very cheap at $1.29 a quart, so I change it after every ride. You can also use gear oil, or any good engine oil. How often you change it is more important than what you put in it.
There are those that say ATF isn't a lubricant, it's a hydraulic fluid. Hogwash. It's an oil, like all hydraulic fluids. If it isn't a lubricant, then what lubricates the gears, clutches, bearings and shafts in an auto tranny?
I use the ATF in my KX250. For my YZ250F, I use Shell Rotella 10W40. I change it every 3-4 hours.
Of course, there will always be the nay-sayers that will swear that you are leading your machine to an early death if you don't run those so-called "moto-specific" JASO MA oils, or that you are going to do damage to your clutch. And that's just such a crock. There are many motorcycle oils that do not have the JASO MA rating, as well as many automotive oils that meet or exceed the same standards but simply haven't been submitted for certification because they aren't targeted at the motorcycle market. But, since so many dealers (that make a huge profit on oil sales) try to convince riders that they are doing their machines a disservice by not using these products, and the myth is perpetuated on sites such as this, the debate goes on and on...and it will probably never be resolved. But if running that high-dollar moto-specific oil makes you feel better, then by all means, use it, there's something to be said for the feel-good factor, after all.
