Water has been contaminating diesel for years...... that's why you have a fuel filter. Part of any normal diesel service regime is to drain the water from the filter. I was doing this over 10yrs ago.

As for water in petrol.....

Yes ethanol/methanol absorb water, but on modern cars this should not be a problem at all. A Subaru certainly shouldn't experience issues with this, unless the fuel system is fubar.

I've ran 20% meth mix for over 2yrs, with the car standing for months on end without use. Not one single issue with OEM lines and hoses...... I'm certainly not the only one.

 

I'm not sure if Toneh uses this site anymore but it'd be good to hear his eventual findings (I think it was him that started the whole mapping debate).
There seems to be a common trend on the links I've thrown up. 99.9% of people seem to think it's fine or just as good as Vpower but that 0.01% have had problems with Tesco 99.