You already have because you bought the green one!

This is exactly the reason. Both have the same engine & configurations but the MDX is rated using premium. It's all about marketing, they could have just as easy said the MDX can use regular but they'd have to change the rated horse power to 255 and visa versa with the Ridge. With luxury cars, owners are more impressed with more horse power than the fact it can run on regular so they market it as such knowing owner won't balk at having to use premium to get that HP rating.adjmcloon said:Does the Acura require that you fill it with premium fuel?
Today's auto technology can adjust the timing +/- in real time for higher octane gas. This could account for the extra 10 ponies in the Acura vs. the RL.