ic2 works fine
mekanism works fine

put both together and i get a bad crash i cant recover from : (
https://imgur.com/a/orc84 - setup
http://pastebin.com/GR8PzfKA - crashlog

i know the log says ic2 upgrade module but from my testing it doesnt happen with the ic2 tanks

update from the ic2 guys

Mekanism isn't respecting the doDrain parameter of IFluidHandler, so it is
empting the tank in the calculation drain to leave nothing for the actual drain.
They should change
https://github.com/aidancbrady/Mekanism/blob/master/src/main/java/mekanism/common/tile/TileEntityFluidTank.java#L554
to if(canDrain(from, null) && doDrain)

I'm having a same kind of issue. Thanks for pointing in the right direction. Hopefully I can fix it. The provided "fix" from the IC2 dev's does prevent crashing, but also prevents extracting anything at all.

I'll let know if I have a fix

Changing https://github.com/aidancbrady/Mekanism/blob/master/src/main/java/mekanism/common/tile/TileEntityFluidTank.java#L556 to

return fluidTank.drain(maxDrain, tier != FluidTankTier.CREATIVE && doDrain);

Should properly simulate draining.

I should have seen that comment earlier... Created a pull request with the fix. (second one.. first one had wrong base branch)