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Changing the oil...

Joined
Jun 19, 2007
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#1
I am kinda new to the dirtbike thing and am fully aware of how important it is to change the oil and ensure all maintenance is done correctly and when it should be. Hell.. your bike will last A LOT longer if you take care of it; this I know. But what oil to use is new to me when it comes to dirt wheels. I spoke to my dealer and he says that it is important to use oil designed for motorcycles. How I took it was "You must buy our highly over-priced oil!" Or does his reccommendation hold some water. Should I spend the extra money for the "Motorcycle" oil or can I just stick with good ol' Castrol GTXs?

By the way I am now riding an '06 CRF250x. I am not racing yet so my bike is not getting beat to hell yet so any advice about maintenance intervals would be greatly appreciated.

-Schnot
 

Jaybird

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#3
Hard to go wrong with whatever the mfg recommends. But their recommendations often leaves open the door to many oils.
Chosing the correct viscosity is probably more important than looking for a "motorcycle specific" oil.

Motorcycle oils (oils that have been certified as JASO MA, MA1, MA2) have very little testing requirements that speak to the chemistry and integrity of the oil, but they have gone through a frictional test to determine if the slip charactoristics are within the ranges deemed as suitible for wet clutch motorcycle operation (clutch and motor lubricated by same oil).

Many other oils that are not marketed towards the motorcycle niche can also pass these JASO certification standards, yet they are not designated as such since they are not really peddled to the moto crowd.
Many of the non-jaso certified oils are far more robust than many of the JASO oils avialable.
JASO states that an oil that has a service catagory of SG or later can be certified JASO MA if it meets the frictional testing requirements. Thing is, SG oil is a now an obsolete service catagory. Oils that carry the latest certifications such as SM or GF-4 are far better oils than any of the SG oils of old.
The way the JASO standards are set up, you could actually pick a JASO cerified oil that indeed passes the frictional benchmarks, yet may not be a very robust oil at all.
Using a moto specific JASO certified oil is not much insurance of anything at all, other than it probably won't make your clutch slip...at least in the first couple of hours of run time...

Finding an oil that will make a wet clutch slip is going to be hard to do, but there are some that make shifting feel different than others. Best bet is to try a fluid that others have been using with great success.
The heavy duty engine oils (that are often marketed to the diesel crowd) often make the best choices for dirt bike engines. 15w-40 Shell Rotella T, Mobil Delvac 1300, Chevron Delo 400 all make good choices for dirtbike engines, and at great pricing. Some like to use the "synthetic" offerings of these oils in 5w-40, more for the "feel good factor" of using a "synthetic" oil. But I find the conventional 15w-40's to be able to last longer. (I know this sounds contrary to conventional wisdom about synthetic oils, but these types of synthetics (group 3) are full of polymers that are the weak link as far as the oil holding viscosity for very long)

No matter what you chose to use, make certain that you can afford to change it out often. The contamination of a dirt bike clutch pack will foul the oil before it is out of grade and low on additive protection.