Cold weather can reduce mileage due longer warmup time. Another factor is more rolling resistance from the tires. Around here, a factor is our winter blend of gasoline. Extra ethanol and oxygenators are added (by EPA mandate). Two weeks ago, our local newspaper reporter was able to run 4 tanks of fuel through his vehicle: two with our winter blend and two outside this location with conventional blend. All driving was under approximately the same road conditions and speed, mostly highway. He reported a 2 mile per gallon reduction for our local blend. I know this was not an exacting test, but it does show the same trend I've expereinced. (I keep a log of miles and fuel used in all my vehicles.) In the winter, I drive a 4x4 Jeep Cherokee, 6cy, 4.0 L engine. In summer, it tops out at 20 MPG and falls to 16 in the winter. The temperature was 15 F below 0 this morning, and it took a trip of 7 miles to bring the engine up to temperature.

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.