The only fuel additive I really believe in is upper chamber lubrication. I do so about every 5k or so, and while I have no idea if its a placebo effect or not, but my engine tends to quite down after each application. I don’t really notice a mpg difference.

I do moderate hyper milling, just need to learn to be comfortable with drafting.

Nitrogen Filled tires:

I admit it, I’m lazy, I hate crawling around on the ground to refill the tires. I’ve been wondering if I would go this route or not. I’ll wait for more competition to come into the area and lower prices.

I have thought about moderate over inflation. I’m still iffy about this one. I’m not an aggressive drive and don’t follow to closely. It is maybe once a year I have to SOBH.

I’m surprised you didn’t bring up washable air filters as being rather flaky in the saving of fuel department. I’ll take my chances with tire skirts.