G'day folks,
Yep, we've noticed the anomaly of the Imperial mower fuel mix ratio [as given on the cans] before, here at ODK.
My own thoughts were, that this was due to Victa doing a 'partial conversion' from Imperial to Metric units, with some rounding up involved.
Two fluid ounces [which is 56.6mL] of oil to one Imperial gallon [160 fl oz] of petrol would give an 80:1 mix ratio.
As maxwestern has calculated, 57mL to 5L gives 87.7:1 mix, and 62.5mL would be needed for 80:1.
Maybe Victa had concluded that, given the accuracy of the measuring vessels likely to be used, any mix between 50:1 and ~90:1 would be OK!
80:1 not being available from the pump would (presumably) be more of an annoyance to owners of these machines � who may have been used to (with 4 strokes) just putting fuel in, checking the oil level occasionally and taking it to a mower shop for an oil change each year. Possibly their local BP servo would put a mix of BP zoom outboard and straight petrol (to make overall 80:1) in the mower can for Imperial owners.
I wouldn't think that any servo, even back then, would bother with such fiddling around. They'd just fill the can with Zoom Outboard - as it says on the tin!
Zoom Outboard was then dispensed either from a bowser, or by measuring jug [1 gallon size, or later on 5L] from a 200L tap drum - depending on the servo's sales volume of the product. Bowsers for Zoom 50 were common at boat marinas.
Mower/OPE shops in those days would only have Zoom 25 available as premixed fuel, but would have 2-stroke oils in stock.
The 200L tap drum setup was what these shops used, and the fuel was mixed in the drum from Zoom Concentrate and regular petrol delivered from a tanker truck.
