They rarely specify it's imperial gallons so it's definitely a source of confusion. Still a moot point though. I did direct conversion to miles per US gallons from the litres/100km figures the manufacturers give. They're basically claiming a full size SUV will get the same fuel economy as a small sedan gets in the real world. False advertising. There needs to be a change in the way vehicle fuel efficiency is measured in Canada. I usually go by the EPA since the test is more stringent and closer to real world conditions.
Yep, US EPA MPG testing is now fairly accurate in real-world use imho, as long as it's tested correctly.
At the same time, it's easy to beat or to miss EPA fuel economy spec depending on circumstances.
In my '08 Focus, I regularly saw 42-44mpg on long trips, with 65-75mph sustained speed, A/C use, etc. This is with the 5MT. In the city I saw low to high 30s depending on time of year. This is a fair bit better than the EPA estimated fuel economy, but on those long trips (Dallas to Knoxville and Dallas to Los Angeles round trips) I was able to maintain speed for hours on end with very little throttle adjustment. I also used better motor oil and had an aftermarket air intake system and ECU tuning.
In my '12 TC 6MT, I am seeing ~22.5 mixed, probably 60/40 city/highway. Even if I reset my computer and do calculations after fillup, I still only hit 28 or so highway, which is a bit disappointing compared to the 23/31 EPA rating. To be fair, the tollways around here I drive on has packs of cars doing 80-85mph, so I'm sure that takes a toll, and I do have a bit of a heavy foot around town, it's close enough to call that fairly accurate. It's still a pretty big let-down from the Focus though.
I think what it boils down to is people need to be better educated on the testing methodology and calculate based on their typical usage patterns. It's a good reason why you might be able to get 28mpg on 1.2 gallons in a Tahoe in perfect flat conditions @ 60-65mph with no accel/decel, but that's not really indicative in typical usage patterns. The GM LS-series motors are really efficient once cruising, but if you're slowing down and speeding up, or get a bit of a lead foot when you do need to speed up, and that fuel economy will plummet like a rock.