A bit late with the answer but I changed the oil on my L5a today and in a completely drained and dry headstock, 1 litre of oil took the level up to about 1/3 between the 'Low' and 'Full' marks on the sight gauge.
I used 75/90 synthetic gear oil simply as I had a bottle - EP stuff for differentials etc probably not a good idea as the layshafts run in bronze bearings.
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