What It Is...
Their claims are rather vague. They don't specifically claim to improve gas mileage and performance, although they definitely do hint at it, but their main claim is that it will make your exhaust "smell better". But when you say "Affects the properties of the gasoline or diesel fuel, causing it to burn cleaner and more efficiently", that sounds to me like you are making a claim. According to their literature: "First of all, whenever you put an The OCW SmogBuster Disc on for a client, always start the vehicle and allow it to run for 15 -20 minutes in order to allow the engine to warm up. This will allow all the emissions systems to start to function properly. Have them smell the exhaust as you are cleaning a spot on the tank to affix the OCW SmogBuster Disc on. After approximately 5 minutes invite them to smell the exhaust again, invariably they will take a second or third whiff of the exhaust, as it now smells like hot air from a hair dryer than [sic] a tail pipe of an automobile. In just that short amount [sic] you should be able to determine a significant reduction of emissions to the point that a dramatic change is noticeable just by smelling the exhaust."
To me it sounds like something out of Star Trek. When I examined the disc I saw no power source to actually power the disk. Then I took it to a computer manufacturer here in town and had them test it in their labs while I watched. The disc showed no activity whatsoever. No voltage was measured, no RF (radio frequency) and/or microwave emissions was detected. It may be able to store a program like a computer disc, but a computer disc without a computer is worthless.
I used my 1997 Buick LeSabre 3.8 liter gas engine and my 1983 Mercedes 300D 3.0 liter turbocharged diesel as the test vehicles.
Test 1 Phase 1... MercedesI started with the Mercedes, filled up the fuel tank and noted the start mileage. I then drove it for three tankfuls and got my baseline mileage of 41.3 mpg. There is no emission test for diesels so one was not done.
Test 1 Phase 2... MercedesWith the tank full I installed the The OCW SmogBuster to the bottom of my fuel tank according to the instructions. As far as visual indications, I did not notice any difference in the amount of smoke at any point of the test. I wasn't about to "sniff" diesel exhaust.
I drove it another three tanks fulls and, with the OCW SmogBuster installed, got an mpg of 41.5. I ran Phase 2 of the test again and got an MPG of 41.2.