I just received the latest update to my Automotive Bible.
Each year, World of Wheels Magazine puts out an annual Buyer's Guide of each automotive model available in Canada. Using their data at time of publishing, I've complied some charts on the most fuel efficient vehicles, sorting by category, efficiency and price. Unless specified otherwise, each vehicle is listed under its basic engine and transmission configuration.
While compiling this list, I strove to choose models based on their best highway fuel efficiency. Not all models available are listed, and there were some models that did not have their efficiency ratings available at time of publishing. In either event, I encourage you to pick up a copy, and even get a subscription. I'm not a gear-head, but I've been subscribing to World of Wheels for almost 20 years. Its a great magazine aimed at Canadian car buyers.
One last point, every model listed is shown with its rating for its basic engine/transmission combo. Upgrade the model to a different engine, and you get much different results.
Cars by category
Cars by efficiency
Cars by price
There's a couple of things worth pointing out. Unless its a family or economy class car, it doesn't make the cut. That includes minivans, SUVs and pickup trucks. That's not to say you can't find an efficient model of truck, SUV or van, but if you need one of those then your priorities include items that may usurp efficiency. That's not a condemnation, I own a mini SUV myself. But the point of these charts is best efficiency available. Not cargo capacity or off road capabilities or whatever.
Just because a car is Japanese, it doesn't necessarily mean its the most fuel efficient. They do have many models represented (and lead in most categories), but there are some surprise showings by North American, European and Korean models.
For the most part, straight gasoline models do almost as well as their hybrid variant (Prius and Civics notwithstanding). If you are on a tight budget, I submit you can buy a gas burner and do it with pride.