On Oct 14, 4:05*am, harry wrote:

snip


Depending on the ratio, you can sometimes tell by putting a drop of
the (mix?) on glass. When the petrol has evaporated, if there's any
oil you can see the oily smear on the glass when you hold it up to the
light. *You might have to rub it with you finger to make it become
visible.

Works just as said. Even 1 to 50 ratio (2%) will show an oily residue.
But lacking a decent test surface, using up the fuel in a standard
machine and mixing fresh is less nerve wracking.

Joe