I don't think you can do that with any conviction. Perhaps if you formed a sample group of maybe 1000 vehicles, with double-blind testing for all participants, and then had your conclusions peer-reviewed by other un-related researchers studying the same research area, you might be able to have more confidence. But most contributors to this thread seem quite content to go with anecdotes and rumours.
There will be a mass of primary scientific research re. E5 / E10 on the net if anyone's genuinely interested enough to go and read it.