I have a diesel farm tractor that does’t get a lot of use anymore, so I either buy #1 or add a gell-PREVENTING suplement all the time.
But I just googled “Diesel 911” and got some initially conflicting info here:
It seems that the stuff in the red bottle is a “rescue” or “emergency” product, but doesn’t (according to their own website) “prevent” gelling.
I use their “Diesel Fuel Supplement” in the gray or white bottle for that.
I still learn something every day. I had never heard of these “rescue” products before today.