For the test to be valid, the driver can't know the type of oil in the car. The biggest MPG factor by far is how the driver operates the car. A subconscious bias in gas pedal operation will affect the outcome. Operating the heater is used has a huge effect on how our Prius chooses to turn on and off the engine while the engine is warming up.
That’s not exactly true. I suppose if you want to know the impact of oil spec on fuel efficiency, you could concoct a test in which you blind the participants to the oil and look at the results.
Or you could, perhaps, find records on cars for miles already driven, on what kind of oil, and tease out the impact on mileage through statistical analysis. You could bench test the equipment, or concoct a rental car fleet test…
Either way, folks in this post indicate that the fuel efficiency delta is going to be very low, maybe immeasurable, and certainly hard to discern reliably.
But back to the validity, you have one person reporting their results on two oil weights. It’s a small sample, and I would not place much weight in whatever conclusions are made, maybe something is discovered…. I’m interested in seeing what happens, see no issue with the validity of this very small sample test, predict the test reveals nothing actionable, and always applaud efforts at measurement.
Blinding this test to prevent bias? Not sure that this is something to chase down here.
Also, kudos to the OP for achieving these very impressive fuel efficiency numbers regardless of oil weight.
