It can but is not necessary because 1) oil will naturally diffuse from areas of higher concentration to areas of lower concentration



and


2) return line will mix the oil and fuel.


Putting it in 1st requires that you know how much fuel will be bought. I frequently buy about 10 gallons of fuel give or take and there has always been sufficient capacity to add 10 oz (1/3 of a quart) to the tank.

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85SD 240K & stopped counting painted, putting bac together. 84SD 180,000. sold to a neighbor and member here but I forget his handle. The 84 is much improved from when I had it. 85TD beginning to repair to DD status. Lots of stuff to do.