Are you seriously saying that direct injection is responsible for increasing an engine's efficiency by over 30%? That is diesel engine territory. Diesels get their additional efficiency from a lot more than direct injection.
I don't know what the writer was thinking when he wrote that, but its just bad journalism.
Allow me to backup my info a bit more. Here are some actual numbers on the Elantra's straight hwy mileage per a Popular Mechanics review. It still gets quite good mileage, but 50 mpg at 80 mph is not going to happen unless you can drive downhill to every destination you travel.
http://ecomodder.com/forum/showthrea...tml#post285060
