Your petrol of choice ??

[Bob Olive]

Since covid lockdown started I've used Sainsburys because it is card payment at the pump. Recently I've taken a bit more interest in the grades and see Sainsburys offer E5 and E10 and the E5 is £0.32 more per gallon than E10.
Our more elderly members may remember Cleveland Discol which was available up to the 1968, this was a blend of petrol and ethanol, at what concentration is not known various sources say from as low as 5% to as high as 20%. This was developed by Harry Ricardo, National Distillers and Shell oil in 1928, so in all probability a lot of Sevens may well have run on it.
Judging from some of the 22FZB carburetors that I've had to deal with where the inlet filter is severely corroded into the the carburetor and had to be cut out I don't think this is a new problem.
I think the problem with ethanol is if you get any water in the fuel tank, this will combine with the ethanol to produce an acidic compound, so drain any water out. This can be easily detected and drained off on gravity fed front tank cars if a glass bowl Brigs and Stratton filter is installed below the tank, see photos. 
Faced with my daughters boyfriend filling her VW Beetle up with diesel I had the job of sorting it out and ended up with 4 gallons of almost neat diesel, it went in the Seven to give a 50/50 mix which loved it, a bit smelly when cold but OK when hot.

Agree with Dave here about diesel mixed with standard petrol (my experience for the same reasons as the VW error reported here...) It also reminds me of a late summer evening many many years ago, when having been delayed at the pub (after a very successful cricket match...), in the gathering dusk I mistakenly filled my mower with 'greenhouse paraffin' when the tank ran dry - in order to finish cutting the third of acre of grass before total darkness set in, and whilst it sparked a bit, it started fairly easily, smoked quite a lot, but finished the job with no obvious damage or after-effects to the mower engine. Seven engines seem to be very tolerant of almost any fuel, its just the possible corrosive effects we have to think about.