Making switch to Mobil 15-50W - question

[Mark W]

I was talking with a guy who works at a local cycle shop about switching to Mobil 15-50W syn oil in the KDX220 tranny. He said that if I have been running BelRay Gear Saver 80W (which I have) that it would be a msitake to make a change to the synthetic stuff as it would wear out my clutch disk quicker. He said that the best/only time to make a switch would be when I need to service the clutch.

Is this blowing smoke or is there some merit to his remarks?

Mark

 

[Rich Rohrich]

There is some merit to what he told you. Research has shown that clutch slippage in wet clutch motorcycles is most often caused by varnish buildup on the clutch plates, as well as the normal deposits that come from long term use. I've seen on a number of occasions where switching from mineral based oils to synthetics on old clutches seems to enhance this varnish slippage effect. When I bought my used high mileage XR650 I tested this specifically on the original clutch. It had minor slippage on the Castrol mineral oil that the previous owner used and a lot more as soon as I started using Mobil 1. After a fresh set of clutch plates and a ton of engine mods Mobil 1 never caused clutch slippage during the bike's life time. Not exactly the most scientific study but it certainly synced up with the experiences I had on my drag bikes and other people had in similar dirt bike applications.

In situations where people break in a new bike on mineral oil and then switch to synthetic, I've never seen a problem. The time on the clutch seems to be the key factor, so it's probably worth considering what he told you.

There is some additonal info on Mobil 1 here :
http://www.ericgorr.com/techarticles/mototech_june_1999.htm

 

[Rhodester]

I bought my KDX used. I don't know what was in the tranny at the time but the clutch got to the point after a while that it would slip a little under a hard load when shifting into the higher gears (I'm 223lbs). I decided to run ATF due to its super detergent qualities as well as its ability to increase the stickiness of the clutch plates. It seemed to work well. My tranny then decided to occasionally want to resist up-shifting out of 4th gear (after a time). I wasn't sure if this had any thing to do with the ATF or just old age and wear of the gears, but I decided to run Mobil 1 15-50 synthetic to see if that improved the shifting. It didn't completely eliminate the problem but made a major difference. It almost never happens now and my clutch doesn't slip at all. Perhaps the ATF cleaned the glazing off of the clutch plates and so they are now clean enough to not slip with the slippier (is that a word?) synthetic Mobil 1.

 

[skipro3]

My bike started life on a regular diet of dino oil in the tranny. I switched to Mobil 1 15-50 (red cap) about a year ago without any noticeable affects other than the thing was MUCH quieter. After installing an auto-clutch, (keeping the same clutch plates) I used ATF at the recommendation of the manufacturer. So much aluminum was showing up in the fluid, that I could not see through it, even after changing the ATF and running for only an hour. That scared me. I tore everything down and could not find anything that was aluminum wearing enough to justify the copious amounts of flecks I was seeing in the ATF. I changed back to Mobil 1 by flushing out the ATF and filling with Mobil 1 after 15 minutes of riding. (Just enough to warm it up). Now there is no meal flecks and the tranny is a quiet as ever. One other thing: the ATF made mis shifts going from neutral to first, as well as the tranny dropping out of first to neutral under load when used. I sure didn't like that. I realize many here use ATF but it will never go back into my bike after seeing that much metal, that many false first gear shifts, and that much clanking noise from my tranny when used.

Beware of Mobil 1 15-50 and be sure you get the older blend if you plan on using it. It's my understanding that it is reformulated and already on the shelves. Learn to read the codes on the circle lable so you know you are using the correct stuff.


According to Mobil, the latest formulation of the red cap has some friction modifiers but it's probably not enough to cause clutch problems. An alternative may be the yellow cap (Truck and SUV). The yellow cap is very similar in formulation to Mobil's Devlac 1 gas/diesel oil (it's rumored to be the same thing). Most gas/diesel oils work very well with wet clutches because some of the diesel manufacturer ratings such as the Allison C4 are for wet clutch operation. Fleet oils also have generous amounts of anti-wear additives. Delvac 1 works very well in the KDX but it's harder to get than the yellow cap. Delvac 1 and the yellow cap are a 5W40 but have a reputation of being very shear stable, so the 5W part shouldn't be a problem. And when warm, it's actually a little thicker than the Mobil 1 10W40 motorcycle oil. I currently have Delvac 1 in my KDX and shifting is better than with Mobil red cap, Mobil 1 10W40 MC oil or Amsoil 10W40.