As a Six Sigma Blackbelt, changing more than one variable in an UNCONTROLLED fashion can mask the effects of the primary variables and their interactions. If you'd like, I can construct a legitimate Design Of Experiment including all variables you believe might be affecting your mileage, and then you could try them one by one...
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_____ I fully concur with this advice. There are, unfortunately, a number of environmental variables, many of which are not measured. For example, i just completed a 1,000 km round trip through parts of the BC coast mountains. On the way to my destination i got 13.1 km/l, while on the way back it was only 11.5 km/l! The major differences were air temperature, routing, vehicle speed and air speed/direction.
The variables that play a role are: - elevation, - average grades of hills/passes (1,400 m to 1,750 m), - ambient temperature, - air humidity, - average traveling speed, - percentage of time spent in which gear (city vs highway), - tire inflation, - number of passengers, - wind speed, - type of road surface, - state/condition of engine (air/fuel filters, injectors, compression, coolant temperature), - amount of fuel taken at refill (not consistent), and - fuel (type/quality).
There are indeed well known standards for "Design of Experiments" that aim to determine all the variables that will affect fuel consumption. This is not a trivial undertaking, and requires a fairly large number of vehicles to take part in order to get a statistically significant result. In addition, all measurable variables _must_ be measured all of the time during the tests. As a result, these tests are essentially impractical to carry out by laypeople.
The best way to determine the efficacy of any fuel additive (such as MMO) is to run the car(s) on a calibrated dynamometer under precisely controlled conditions on a tank of "standard" petro diesel fuel, then refuel with exactly the same amount containing the prescribed amount of MMO. This is quite feasible, but costs a good deal of money.
Incidentally, i checked out the Walmart store where in live in BC, and MMO is simply not available. There were two brands of "injector cleaner" claiming better engine performance after use. Personally i am suspicious of fuel additives. The oil refiners who produce these fuels are the experts in the area of additives. If the supplemental fuel additives were really needed, then they would already be present in the fuel at the pump. Finally, due to the lower sulphur level in current Canadian (and US) diesel fuels, a number of injection pump failures have been reported. Apparently the rotating vane pump designs are more sensitive to lower fuel lubricity. The older piston style pumps (as found on 300SD and 300D Turbo engines) do not seem as sensitive. Despite this, i add about one cup of ATF per tank refill to make sure that the petro diesel is slippery enough for the pump to keep working properly. This recommendation comes from my Mercedes Specialists in town. Lack of lubricity in the fuel is _not_ an issue when you use biodiesel or some blend of neat vegetable oil.
You can get it here...
Veggie oil for the win! :)
It's amazing how much smoother my car runs on the stuff, but it does come at a slight cost of power. Not that 77hp was much to start with, but my climb of the hill away from work at night is an exercise in frustration for those who get stuck behind me...
Since going to VO I've noticed one thing for certain; I'm saving a lot of money on fuel. :)
-tom!
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