Petrol,around the baltic
 

Considering going around the Baltic Sea next summer and wondering of the availability of petrol (distance between filling stations).
If needs be would prefer lot fit larger tank than carry can.

If you are following the cost lines, more or less, of Sweden/Finland/Estonia/Latvia/Lithuania/Poland you are probably just fine with a reach of 300 km.

Sweden is no problem what so ever, even on the country side. Some of the more rural areas of the northern Finnish countryside might probably be the only issue, if you go a bit north and more in land. I experienced Estonia/Latvia/Poland to have a lot of places to fill up, and rarely went more then 150-200 km without filling up.

if you have 300k range you´ll be fine up in northern Finland and scandinavia.
Baltics you´ll manage even lesser range.