I don't know anything about the question you asked about the bypass, but I do know something about fuel gelling as I run a fleet of medium duty (25,000GVW) diesel trucks and since my company distributes automotive chemicals, including anti-gel compounds. Also, we don't use Cummins engines, I have trucks running Cat engines, plus a couple running Mercedes and International engines. I don't know if any use a bypass system, but if they did, I'm not sure that it would solve the gelling problems we've experienced.
First, most retail fuel centers and most fuel distributors located in colder areas of the country seem to mix their diesel into a winter blend starting around November and continuing through winter. So for most people who buy in fairly small quantities, gelling is rarely a serious issue until the temps drop below 5 or 10 degrees for fairly extended periods of time.
As much of the upper midwest is currently under conditions where the daytime highs are in the low teens, and the lows are often below 0, we are under conditions where some thinning of the fuel is helpful. That said, most of our gelling troubles with our fleet seems to be in the fuel lines, not in the tank, we believe that the lines, being thin tubing allow for too much surface contact with cold walls of the lines and therefore gel.
Thinning the fuel can be accomplished in one of several ways. Mixing different grades of fuel, as you did, will accomplish the goal, it is not totally reliable, but it does work. Slightly better is mixing in some kerosene with diesel as it is even thinner. Of course, for road use this is not techincally legal, so if you have a powerstroke diesel in your truck you should be aware of the fact that mixing is not always allowed under law, but it beats the heck out of having gelled fuel lines!
Generally I recommend something that is easy, and cheap, and this is what we do with our fleet. We add any of the commercial anti-gels that are available at auto parts stores, fuel centers, even many convenience stores sell it. Cost is usually a few dollars a bottle and a bottle can treat up to 100 gallons, depending on the brand.
For folks who keep their tractors in relatively exposed areas, when temps drop this low (+10 or colder for days), adding an anti-gel or mixing in thinner diesel or kero is a good thing. But my experience is that most people will rarely need to worry about gelling unless they face prolonged cold temps that last for several days. Or unless they buy bulk fuel and buy it in the summer months or buy it from a supplier that does not mix/winter treat his diesel.
When temps drop below zero, and you are running equipment, then the likelyhood of a fuel line freezing is probably greater than fuel in your tank gelling. Again, that is my experience, and I believe it is based on the relative high surface expose the fuel is exposed to as it travels through the thin fuel lines.
