Manufacturers spec B&C oil outputs for the 3120 is between 30-54 mL/min while for the 880 its between 17-38 mL min.
However, what really matters is that any oil that is output actually reaches the bar on the other side. When I did some measurements a few years back I found that most of the extra oil output by the 3120 is lost at the nose because of the centrifugal forces involve. This is useful for plunge cutting but for milling It makes more sense to use an Aux oiler to add the extra oil after the chain had gone around the nose. These measurements were trigged by (before I did those measurements) the time when I spent couple of days milling with a 3120 in seriously hard Aussie hardwood and although the saw was consuming a lot of oil I could not understand why the chain was still dry so I then added an aux oiler and this solved the problem.
Both saws suffer from the same flaw of a forward facing exhaust so that when milling the top half of a log the exhaust reflects off the log back up towards the operator.. This may not worry folks in cold climates so much but here when its 100+F in the shade that hot exhaust just adds to general fatigue. This was my solution to this and while I was at it I opened up the exhaust outlet.
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What I did not realise at the time that this means the sawdust then falls into the exhaust stream and blows it a away from the operators feet. This means minimal sawdust buildup so the operators level along side the log stay the same throughout the milling operation.