Give it an occasional slosh Russ to coat the top.
As a point of interest the firm bought a lot of John Deere tractors (when I worked), most of them are in constant use so no problem but the crawler I drove in the harvest stood idle for most of the year apart from regular starts to circulate oil, the instructions from the Deere dealer were to store it with tanks brim full to prevent condensation forming in the tanks (tanks were plastic BTW),.
The reason for this was the injectors did not like water (common rail engine) and at £1000 UK a time you were not going to be the best liked guy on the payroll if A. the thing would not start when you wanted it and B. it cost 6 grand plus labour to get it going .
I looked after that thing until I retired then it gave problems starting, there followed a three way argument (negotiation) between the firm, Deere and the fuel suppliers as to who stood the cost, turned out the fuel was at fault as many other farms reported the same fault, which brings me nicely back on subject.
In our discussion here we are assuming the fuel we use is mixed correctly, it is quite possible Ethanol might have got into some supplies in greater percentage than stated or any of the other additives for that matter.
Scientific reliable testing is needed.