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Old 09-11-2011, 01:38 AM
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Default RE: 4C crank case drain

Well, the Saito petrol engines are now rated to run at 5% oil mix, afaik.

They started off with a 3.5% mix, but experienced premature failures of the big ends ... I think that's the story, anyway. The big ends are plain bearing, afaik; exactly as per the glow version of the engines.

Yes, they say that petrol has some lubricating properties; and that methanol has no such properties - so the effective "oil mix" of the Saitos would be a little higher than 5%.

We know that a 2% mix provides adequate lubrication on industrial petrol engines. Admittedly, these usually have needle roller bearing on the big-end and the little-end. But, 2% seems to provide adequate lubrication within the cylinder and also for any ball-races that support the crankshaft.