Ok, after some tests, it appears to be directly connected to GregTech and NEIPlugin+RC/BC/Forestry, as I still get 0.5-1 sec delay even with only NEI, NEIPlugin, IC2, Railcraft and GregTech 2.72 installed..I will blame my crappy computer for now :(..
Ooooh, so diesel DOES equal BC fuel?
Why isn't it showing up as such on NEI, then...
Squeeezing BC fuel can/capsule