Can anyone answer the proverbial questions regarding not only which is the best octane level of gas for the Lexus CT 200h, but what brand of gas works best for optimal mileage and why? The manual says 91 octane, but the dealer says 87 is perfect for all four cylinders and anything more than this is just wasting money; and other Lexus owners are cringing that I would anything less than 93 in the car. Also which brand of gas works best? The oder from best to worst that I have been quoted is Sunoco > BP > Chevron > Mobile > Shell and that unbranded gas is BAD!!! Incidentally I am getting 40-42 mpg and an occasional 44 mpg using only premium (using AccuFuel app on an iPhone to calculate - 2 mpg less than the number given by the car gauge), but find it hard to get to the "better" branded gasolines. Finally, how much of a decrement in non-mpg performance (i.e. pick up, top speed) can I "expect" if I use only 87 octane; or stated differently, can I "expect" to get significantly better non-mpg performance by always using 93 octane?