EP 90-ST 90 OOPS

[Andy Pickering]

Just drained engine oil to put in rock oil ST90 and noticed on top of the shelf the cheap crap i used just to check it was running and its EP90 never noticed until now..Only done no more then 20 miles with this in! any long term problems to the clutch..will the ST90 mix and combat the corrosive problems to the engine of the EP90...
Should i flush out with something, been dripping for an hour on nearly its side and its stopped now cant be much in.

[bristolmod]

I'm no expert but....................

EP type gear oil contains sulphur as an additive which apparently will affect the cork plates quite badly. The old Lambretta WSM was very specific about NOT using the Extreme Pressure variety because of this.

Recommendation is, unfortunately, strip clutch and replace cork plates with new, after wiping out as much as the incorrect oil as possible.

Sorry

Chris

[Andy Pickering]

OUCH ...going for mot on saturday so see how it goes then...in the meantime order some plates in readyness..

[noggin1969]

FOUND THIS ON A HISTORIC MILITARY VECHILE WEBSITE.
SAYS NOTHING ABOUT THE CORK BUT DOES MENTION BRONZE

word of CAUTION regarding transmission/transfer case gear oil: DO NOT USE Hypoy/EP 90 based products! They will damage your gears!

The two most important things here are these: 1. Replace the lube with a straight mineral oil.... 90-grade. 2. Under NO circumstances be tempted or persuaded to use Hypoy/EP 90, unless you don't mind rebuilding boxes every couple of months.

Here in England we can obtain straight 90s mineral oil in the form of Castrol ST-90..there are others, too, such as Morris Lubricants' AG-90. You will certainly have an equivalent to this in the USA and Europe. Make doubly sure it is NOT hypoy/EP. If you use straight 90s-grade oil in the transmission-transfer, it makes sense to use the same oil in the differentials, too. That way, there's no chance of putting Hypoy-EP in the gearbox by mistake.

Now for the history lesson.....the Military originally used GO (Gear Oil) and the civilian equivalent gear oil was designated "GL-1" which was a non-Hypoy/EP gear oil which did not affect the phosphor-bronze components in the transmission. After GL-1, came GL-2, -3, -4, and then 5. Each GL number represented a jump forward in technology. (Read, less wear, better protection, etc) GL5 when it first came out had a problem with the sulphur eating up yellow metals - brass - usually used for synchro rings. This occurred only at high temperatures as the oil started to break down. The industry recognized that and the MT-1 designation was added along with additional specification requirements for GL-5. So basically a gear oil with the designation "GL-5 with MT-1" should be safe for yellow metals according to current standards. Texaco, Valvoline, Mobil all make good gear lube and it should clearly state "GL5 - MT1"

Have read on another site flushing out the EP oil with abit of diesel.

[J1MS]

Cant dissagree with any of the above posts, as Ive not done very much reading regards gear oils, other than compairing oil charts and there intended use.....But the one thing that I have read is that EP oils can make the clutch slip, if used in a Lambretta.....

[Andy Pickering]

All flushed out and clean now filled with ST90..Oil that came out clean as a whistle...but will order new clutch plates just in case..not really been run with the wrong oil in, id be more worried if id run it for 100s or 1000s miles so fingers crossed..

[bristolmod]

The wrong oil won't affect the "metal" parts of the gearbox, simply the cork plates- once they're contaminated then they're useless.

Having said that why not try and run it and see how it goes- if it slips then you've not lost anything. If its OK then its a job saved.

Chris