The additive requires 1,000 miles before a second oil and filter change to remove the trapped and suspended varnish and gunk. The challenge is I had not stored two tanks, 20 gallons of gasoline, to keep the fuel constant.
Given the variation in ethanol and refinery output, gasoline does not have a constant, heat energy. Worse, this is the time refineries switch from a winter to summer blend and the gas station tanks are just a mix during the transition. So my next best alternative is to measure the change in fuel energy with each tank and use the accumulated offsets to adjust between the pre-treatment and post-treatment engine fuel consumption.
Two warm-up cycles were completed including a drive and cool-down. The series #6 is the last of the first tank and series #7 is the first of the new tank after 10-15 miles to replace the fuel in the gas lines.
The first chart shows the data adjusted so the end of "N" occurs on the right edge:
By careful timing, the starting temperatures were identical but the shift from "N" to "D" was not well controlled. However, when the thermostat opens at ~85C, there is a notch and plateau while the rest of the engine coolant keeps the engine at a constant, operating temperature:
Close examination shows the thermostat opening is an excellent candidate for a constant temperature state to use for fuel rate measurement:
We can see the fuel burn rate plateaus at these point:
So using my old eyes:
2.75 gm/sec - 1st tank, MAF rate
2.71 gm/sec - 2nd tank, MAF rate
(2.75 - 2.71) / 2.75 = 1.46% higher energy of second tank gas
I'll have to do the same calculation between the 2nd and 3d tanks . . . in about 450-500 miles or another three weeks. Then I'll have to wait to the end of the 3d tank to do the last oil change and consolidate all of the data.
One good side effect is now I have a much easier protocol to evaluate relative gasoline energy content than the earlier, hill climb tests used two years ago. Unlike the hill climb tests that run the engine at peak power levels, these tests are not affected by relative octane ratings.
Bob Wilson