I've reviewed all of them. Nobody is recommending jumping two grades, and the percentage increases in FE you've stated are virtually all based on going from a non friction modified Xw-20 to an Xw-40 oil, or from a dino 10/15w-40 to a 5w-30 syn oil.

Wrong. The one chart you picked proved I was right about the generally 1.5% improvement going up one grade.
Take that picture, showing going from a 40 to a 20 weight, 2.8% total, cut that one in half, and you get 1.4% to get a 20 vs. 30 comparison.
Other statements and tests all over those tech articles and dozens of others show the average is around 1.5%.

Still no.
Maybe you should talk to Garak about the actual statistical analysis involved in calculating gas mileage in the real world. You obviously didn't read anything I wrote, nor did you correctly contextualize the pictures I cut and pasted from your own examples.
Further, outside of the lab-based studies from which you've cherry picked your data, less than 3% is literally within the statistical noise of one's ability to accurately calculate gas mileage in the real world. 1.4% could be accounted for by the difference between filling up early in the morning versus late in the afternoon....

alone. You're misleading the OP with unsupportable claims about his gas mileage being negatively affected when he doesn't even have enough empirical resolution to discern the effects you state will be there. So, even if the negative effects you assert are actually there in the real world (I do not cede this point to you, nor do any of those studies support it in earnest) are there,

you're STILL wrong because the OP won't be able to reliably detect them (that's called statistical insignificance).
You really should read about Garak's professional work done in the field of statistical analysis in the area of accurate MPG calculation. Really.