Mobil 1 15/50 red label

I know this has been asked over and over again here but I need to be 100% on this one. After two months I finally got the 420 back together with new bottom end and case bearings, piston/rings, etc. I used to run it on Mobil 1 15/50 like most of you do here. Brian over at Moto-X here in Laval, Qc. Canada who did my cases says to keep away from Mobil 1, he calls it 'car oil'. He is very knowlegeable and used to road race and aluded that my choice of oil was the cause for my bottom end failure. But then again all of you here are very knowledgeable also! What do you think? Should I go back to Golden Spectro?


Check out the post " Amsoil" on the YZ250 F forum.

I have heard that the motorcycle specific oils have more of something in them (phosperous?) which is supposed to help prevent seizing in high temp/pressure situations. By seizing I don't mean when the entire motor locks up, but seizing which causes things like gailing, scoring, etc.. which can lead to many wonderful problems. I've heard that the car oils don't have this because it causes trouble with the catalytic converters. This is why I have avoided car oils. However this is all hearsay, I don't have anyhing written to back this up.

On the flip side, see the email which I received from Spectro posted in this thread:

It has some interesting information in it about motorcycle oils.

The phosphates (and zinc) are only in an oil in an attempt at preventing galling/scoring *during* a catastrophic occurance. Seems a little late at that point.


MX Tuner

Thanks Guys! I will go back to the Spectro after all. Up mu way the Spectro and Mobil 1 are same price.

I have an 01 wr426 and I've used Mobil 1 5w-50(red) for about 3 mos. with no problems. My buddy also uses it in his KDX gear box with no problems. The guys on the wr side seem to really trust it. This oil apparently doesn't have any friction modifiers in it that can cause clutch slippage like most "car" synthetics do. I have heard of problems with Castrol's actevo oils, and I even had some clutch slip in my VFR street bike using golden spectro syn blend, a motercycle specific oil.

Everyone does say to use synthetic oil after the motor has been broken in. I'd probably use some standard bike oil for break in then switch to synthetic after a couple of oil changes.

just my opinion though.


01 wr426: yz timed, full white bros.e-series, air lid off, hebo hydro clutch, scott's dampner-clamps, protapers, 165 main, 48 pilot, stock needle.

[This message has been edited by s.c.rider (edited October 14, 2001).]

It's odd that you had cluth slip using the spectro. Did that go away when you switched oils? I ask because I've used the spectro synthetic blend in my '01 426 ever since it was broken in and I've had no clutch slip at all.

The Bad:

Automobile oils do not contain anti-shearing agents in them. What this means is when the gears are meshing together and the clutch is being used, the oil will break down rapidly. This will dramatically shorten the life span of the oil. I would never run an automotive oil in my street bike where oil changes occur every 2,000 miles.

The Good:

Since we change the oil in these bikes frequently (after a few hours), it may not come into play as much. If we ran them for days (weeks) without changing the oil it would make a huge difference. If you run an automotive oil in your YZ-F, run a non-energy conserving oil (20w-50).


--Life is too short, work hard--

Sponsored by Yamaha of Cucamonga, Larry Roeseler's Stroker Fourstroke Speed Equipment and Answer Racing,

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