The reason fluid trainers seem to have more resistance, is that the faster you go, the resistance increases at an exponential rate, to mimic wind resistance. But in my opinion, the trainer
overcompensates. I agree with Melly and Kimberly, the effort seems to be easier when I'm on the road than on my trainer.
Now as far as mileage goes, Kurt Kinetic is the only trainer company who says that mileage on their trainer is accurate. I have a Cycleops trainer(which had to be sent back) and a Kurt Kinetic trainer and my mileage on the 2 were very similar for T3...between 20 and 23 miles total. So, no, I don't keep Troy's 25K time trial in an hour