In the late 70's bought a 50's something 18 hp Johnson the old ratios were 16 or 18 to 1 ? ask the local dealer what oil mix was told 50 to 1 at the time that it was not the engine as much as the oil quality 100 to 1 one if the oil is capable Amsol oil is a sinthitic that has worked very well for me in 100 to 1 from chain saw to out board. By a good oil Johnson, Mercury etc. folow the lable on the oil. I have had very bad luck with Penzoil.

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