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Originally Posted by Hops
Did you run 10 tanks of one octane followed by 10 of the other, or did you switch back and forth in some manner?
The extreme of 10 of one then 10 of the other is the least valid because the variation in temperature, season, mechanical factors (tire pressure among others), and gasoline blend would be difficult to control.
At the other end of the spectrum, alternating 20 tanks isn't a great idea because you are blending the two octanes to some extent with each fill (so the actual octane is somewhere in between). Also, I don't know for a fact how long it takes the car to completely adjust to the new octane... is it instantaneous (my assumption), or does it take 5 miles or 50 miles? (Insight on that question is welcome if anyone knows.)...
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I didn't switch back and forth but I did run two tanks of regular (and discarded the results) before starting the test on the regular. The super was what I normally used so no data was dropped.
I realized I was not taking into account many factors but I did try to be as consistent as I could. Tire pressure was checked every weekend (habit I have, not just for the tests). There was a few times I need to drive a substantial distance on the interstate so I took a different car so as not to throw off my results. All traveling was done in town (but even that could be considered inconsistent) and the 20 tanks took me a good 5 to 6 months to complete so temperature would have been a big factor it didn't account for (although it is always hot in Florida
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Originally Posted by blue2000s
I know you mentioned that your test wasn't scientific. I appreciate your admission. Fuels have different formulations at different times of the year, and economy is heavily effected by the air temperature and humidity as well as the other factors you noted.
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That is one of the things I really like about this forum. People here are usually so respectful when they post a reply (I mean that sincerely, I'm not being sarcastic.
) You are right and I didn't even think about different formulations or humidity.
My apologies for not being more thorough but when I did this, I was not expecting to pass my finding off as fact. I did it more out of curiosity because my wife was getting such bad fuel economy in her Land Rover and she was too thrifty to put in 93 octane.