Which engine-transmission-transfer case do you have? There is difference in fuel mileage between the smallest to largest engine. You are reporting 10 MPG. Perhaps you have the honking big V8 in yours. In the past, I owned a '92 Jeep Cherokee and now have a '98 Cherokee, both with the 6 cy in-line, 4 liter engines. In good weather, highway mileage is 20+ mpg, but in this brutal winter, it has dropped to 15-18 mpg. I have found three factors that affect the mileage of my Jeep: 1. Low tire pressure - about 2 mpg. Inflate to 30-32 psi will get this back. 2. Low coolant temperature - about 2 mpg. If the thermostat is not working properly or is rated to open at too low of a temperature, the engine never gets warm enough. For the worst of cold, you may consider a radiator cover, but don't forget to open it as soon as the temperature rises to 20 F or so. 3. Failed temperature sensor, the one that sends engine temperature to the engine controller. There is a little hit for 2-wheel drive versus 4-wheel drive, but not as much as might be imagined because the front drive shafts, differential, and universal joints are engaged all the time anyway. However, this statement holds only for the "full time" mode. If your transfer case has only "part time" drive when in 4-wheel drive, it should be disnegaged for regular driving on surfaced roads. The part time mode is only good for mud, sand, and snow where the wheels are free to slip. Part time mode forces both front and rear drive shafts to turn at the same speed - no center differential action. The drive train may bind and be damaged if operated in the part-time mode on paved roads, and will bind when turing. Small differences in tire circunference between the front and rear tire sets will cause binding in the drive train when in part-time mode on surfaces where the tires can get a grip. The part-time-only transfer case has very limited on-road use - its for off-road and getting out of mud holes.

OK, it's easy to get excited about something when there is no apparent reason to suspect that it may be a scam. Gasoline and Diesel fuel are actually both blends of lots of different hydrocarbon chemicals. Thats just one of the reasons we have computer controls that provide instant adjustment of air fuel ratio's and timing curves. Oh, and yes today's diesels are computer contolled we simply have to wait for the fleet to age and pass before the majority of diesels are computer controlled. IMO, no additive dumped in a fuel tank is going to make a significant improvement in the efficiency, and cleanliness of the older designs. No additive is going to improve today's automobiles. What you described about getting people into this "investment" has all of the appearance of a classic pyramid scheme. The only guarantee's about that are a few people will get some money, and some of them will return it (or at least some of it) under the threat of prosecution. Many will lose their "investment". Pyramid schemes are illegal, and for good reason. If there was any merit to this product, they would have no short list of people (with big bucks) interested in investing, and they wouldn't be looking for the "little guy".

Unless you have specialized equipment, 80 miles is too short a distance to compute gas mileage with any accuracy, because it is difficult to fill the tank to the exact same level each time, and the amount is only a few gallons. You can begin to get an idea of the fuel mileage after using 3/4 of a tank. Alway fill to the same level and keep a log of miles and gallons. After a few tanks, you'll have a better picture. The fuel content does affect mileage. Modern gasolines with up to 10% alcohol has less heating content than 100% gasoline. The reduction in mileage is on the order of 2 miles per gallon. I suspect that you have a V8 engine. Olds did make a samll V8, a 260 in^3, at one time. It was the smallest automotive V8 ever offered by GM. But you likely have a larger engine. The fuel mileage of large engines are more affected by city driving than a samller one. When a car is waiting at a stop, its engine is still buring fuel, but going nowhere. This drops fuel mileage. There are other factors, too.

"Depends" Jerry. Decel fuel cut-off is a very common strategy that even existed in carbureted cars (First one I can think of was Ford Escort 1980). When all we had were carbs, decel caused an extremely rich air/fuel ratio and wasted a lot of fuel while simply releasing most of it to the atmosphere right through the engines tailpipe. So they added fuel cut solenoids to shut the idle circuit down during deceleration. Once we had fuel injection interrupting the injector circuit operation was easy to reduce decel fuel waste, and that is standard across the board with every manufacturer. It's use allows for better catalytic convertor operation as well. Very rich fuel ratios deplete the catalyst of stored O2 and in effect turn them off. Combine that with an additional clutch in the transmission that allows for reduced, if not eliminated engine braking when in overdrive and the engineers are attempting to out gain the benefits of even coasting in neutral and not from just a fuel mileage consideration, but an emissions consideration as well. Today's hybrid vehicles are noted for not having any engine braking at all on certain models. In fact once they go into regenerative braking, and if the battery is sufficiently charged they will rely totally on the mechanical brakes to slow the car down unless "B mode" is used. "B mode" is known as mountain braking and uses the electric motors to fight each other to produce the effect of engine braking. You have to study engine control dynamics to see exactly what compression numbers occur during different engine operating conditions, but as far as the argument that you are burning fuel during a strong decel, "There isn't enough compression to properly burn any fuel that gets into the cylinders" once the manifold vacuum reaches a high enough value. So most of the fuel getting to the cylinders simply gets pumped to the exhaust, which quite often would resulted in a pretty loud backfire. Use the lack of such an occurrance, that cars don't back fire out the exhaust like they used to as part of the proof.