Power Service and Howes - BOTH
A previous TDR Issue (forget which one) compared additives and broke them down into lubricity, cetane,cost per ounce, etc. It covered alot more things, but don't recall them at hand.
I do remember that Power Service was one of the lowest costs per ounce (if not THE lowest) and it actually treated (addressed) more areas than some of the others being compared with it that cost much more.
Howes was not included in the comparison.
I've used both Power Service and Howes and liked them both - never a problem with either.
I'm currently using Howes - 2 oz per fillup in summer and 4oz in winter. I will go 8oz if I know the truck will be outside all night and below zero F. ... and I kept the front end pointed AWAY from the prevailing wind until I started using grill inserts. Also, I now have a garage for my truck to sleep in every night.
I use #2 when ever possible (even in winter) for improved lubricity and power. Right or wrong, I view it like Premium over Regular gasoline. Just my preference. And then I add my own additive so I know what I'm getting.