The ~1% improvement gets lost in the noise of regular driving, except in the winter. I think the difference in cold viscosity can really make a difference in short trips and I noticed around a pretty consistent 2 or 3 mpg difference when I switched from conventional to synthetic. I could feel the engine not having to work as hard for the first couple miles.
Nope. My average with PYB and Formula Shell 5w30 were 20-22 city and 27-29 highway. PP 5w30 averages the same and I expect the QSUD 5w30 next change to be no different.
I prefer SOPUS oils and run whatever I find at a good price when it is close to changing time.
the difference between a 'super low coefficient of friction 0W20' and a regular 10W30 is about 2%. There's no way on earth anyone would be able to tell the FE differences between oils of similar grades/viscosity based on the composition of their base oil, particularly when take into account all of the variables that affect FE.
I don't doubt there's a difference, but that difference is very, very small and next-to-impossible to measure--unless you're comparing oils of vastly different viscosity.
Not one lubricant discussed in this thread uses true synthetic base stocks. Group III does not count.
1. I'm not sure how you can say that, unless you have some inside information that no one else does--most manufacturers don't disclose the base stocks they use
2. the difference between GII and GIII base stocks is actually greater than the difference between III and IV, at least as it pertains to FE--and yet the difference still isn't much. Overwhelmingly, hths and the friction modifiers are more important than base stocks in determining an oil's effect on FE.