It does have the caveat of "for optimum engine performance and fuel economy". I'm not a lawyer. I am an engineer, though. To me, that says that the engine performance and fuel economy will be better if premium is used. It isn't saying that you will or will not damage your engine by using 87 octane. We know that modern ECUs will protect the engine by changing variable valve timing and spark timing to protect the engine.
My theory: official fuel economy ratings are based on using the recommended fuel. It is very possible that Toyota would have to report 24mpg highway instead of 25mpg highway
in an official capacity to the government for calculating Toyota's fleet average if they recommended regular over premium. These numbers matter because there are fines or credits based on how the manufacturer is meeting or not meeting the target. There are definitely heat soak situations where premium will perform better than regular despite the official lab conditions power rating being identical. Recommending premium means Toyota gets to advertise better fuel efficiency and/or input better numbers into their official fuel economy numbers to the government.
IMO, the 31" tire version (1958) also exists to help fuel efficiency numbers. Narrower tire, less ground clearance. Both of these are good for fuel economy testing. Now, you might ask yourself, why doesn't the Land Cruiser or the First Edition show lower numbers? There is basically wiggle room for official reporting when it comes to changing out tires and wheels. Ford got caught up in this a while back because they were reporting fuel economy numbers for the C-max using "general label rule" from a different vehicle all together.
It's been a rough time for the official fuel economy figures for the Ford C-Max Hybrid. When the car was released in 2012, Ford made a huge deal about how it would beat the Toyota Prius V, which was rated at 42 combined miles per gallon, 44 city and 40 highway. The Ford? 47 mpg across the board.
www.autoblog.com
There's kind of a lot to digest in the news about the 2013 Ford C-Max Hybrid EPA label change. In fact, as we tried to really understand how and why Ford <a href="http://green.autoblog.com/2013/08/15/ford-c-max-hybrid-rerated-at-43-mpg-o
www.autoblog.com
"Developed in 1977, EPA label regulations allow vehicles with the same engine, transmission and weight class to use the same fuel economy label value data, since, historically, such vehicle families achieve nearly identical fuel economy performance. Ford based the 2013 Ford C-Max label on testing of the related Ford Fusion hybrid, which has the same engine, transmission and test weight as allowed under EPA regulations. For the vast majority of vehicles this approach would have yielded an appropriate label value for the car, but these new vehicles are more sensitive to small design differences than conventional vehicles because advanced highly efficient vehicles use so little fuel. In this case, EPA's evaluation found that the C-Max's aerodynamic characteristics resulted in a significant difference in fuel economy from the Fusion hybrid."
Automakers can choose to test every iteration, but they often don't because it is costly and it hurts them from CAFE perspective. In order to not mislead or upset consumers, though, you'll often see two similar models get different ratings. The Tacoma TRD Off Road traditionally had lower ratings than the SR5 trucks because it lacks the air dam up front and has larger, wider tires. It is harder, with a straight face, to say that those two will be practically identical. I expect that, in real world, the 1958 will be the most efficient LC (lower rolling resistance) and the First Edition will be the least efficient LC (higher aero drag).
So,
in my opinion, both the premium recommendation and the 31" wheel version exist for the government. They can recommend premium and use the 31" wheel for the official fuel economy ratings to mitigate fines from the government.
Several vehicles on my list as well.
and Araya EV.
