[Dragncar]

Originally Posted by Bill Hanlon

Plus the tape (and anything else you might put on the threads) COULD interfere with the sending unit's connection to ground.

Thing is, its tapered pipe threads. You "must" put some sort of sealant on the threads or it will leak. Don't care if its brass into steel you need something on the threads.
Even if its just neverseize the threads can not be dry. And neverseize can seal NPT threads if the pressures you are dealing with is not too high.
Heck, a lot of guys use it to seal head bolts-water jacket on sbc engines.