On the Cruze example- what adam044 appears to be saying is that any car with a modern/contemporary ECU will return better mileage on premium to the point where it's financially beneficial. I can see where you think consumers would get confused, but if anyone (Chevrolet, Toyota, BMW, whoever) had a way to get an increase in fuel efficiency to the magnitude that adam044 is claiming, they would advertise it everywhere and make consumers knew that the higher cost of fuel didn't matter because they'd be using so much less of it.
After that are cars that only recommend premium for best performance, which I think we agree is pretty self explanatory. The difference between regular and premium in these cars is fairly marginal and using regular will never hurt anything. There are plenty of anecdotal stories either way here, but until someone shows me a repeatable study proving that premium is worth the price, literally all of the evidence says that premium isn't worth the cost increase.
The last category are the cars that require premium, mostly sports cars or motors with very high specific output. These motors either flat out don't work (for long) on regular or the ECU goes into safe mode, which drastically reduces power. I don't think that there's any argument for using regular in this category since they don't exactly work on regular
I understand the emotion of wanting to put the "best" gas in a car and that the additional cost for premium, which usually hovers around $200/year, isn't a big deal...if people want to spend money on something that makes them happy and gives them peace of mind, they should by all means do it. But when
someone starts treating their emotional justification as an empirically proven fact, it's a problem.
