[elhigh]

Truck:
Smoothie wheel discs
Vacuum gauge

Car:
Grid charger

That's it. The rest of my mileage is attributed to advanced nut adjustment.

I invested the money, but not until I had done some serious research on what worked and what didn't. The things that got, at best, ambivalent reviews I disregarded. The things that got rave reviews full of extra punctuation and lots of ALL CAPS I determined were mostly the purview of nutjobs, and I avoided those things and others that resembled them.

Money is hard to come by, and time isn't growing on trees either. I don't have enough of either to waste on suggestions made by folks whose advice includes such brilliance as "I do ROLL the DICE and try things, and indeed I've found things that INDEED WORK! HAHAHHAHAHHA!"

Serious people with calm voices and guarded enthusiasm declaimed the advantages of the grid charger. Damned thing was expensive, but the proponents looked like they had been grudgingly convinced by lots of well-documented testing and provable, repeatable results. So I bought one. It's working.

Now, I'm a lazy dude. After I've put in 10 hours at work wrestling with air conditioners, plumbing, small engine repair and then working on re-siding the house, mowing the yard and medicating the cat, for some reason I just don't have the gumption to add some more siding to the car. So while I have aero aspirations for my rides, they are slow to actually manifest. But those are the only kinds of alterations I'm willing to make at this point, because those are the ones that have the most consistently positive, provable, repeatable results.