If you were to go to natural resources Canada and check the fuel consumption figures you will find that the domestics are actually get very good mileage
from The NRC site for the Aveo
Make/Model Class Eng Size/
# Cyl Trans #gears Fuel Consumption Rank CO2 kg per year
Type $/yr L/yr mi./gal. Class All
City Hwy
CHEVROLET AVEO C 1.6 / 4 M5+ X $1332 1480 32 49 11 40 3552
CHEVROLET AVEO C 1.6 / 4 E4E X $1404 1560 31 46 18 67 3744
And for the Cobalt and Aveo 5
Make/Model Class Eng Size/
# Cyl Trans #gears Fuel Consumption Rank CO2 kg per year
Type $/yr L/yr mi./gal. Class All
City Hwy
CHEVROLET AVEO 5 S 1.6 / 4 M5+ X $1332 1480 32 49 11 40 3552
CHEVROLET AVEO 5 S 1.6 / 4 E4E X $1404 1560 31 46 19 67 3744
CHEVROLET COBALT S 2.2 / 4 M5+ X $1386 1540 31 48 16 62 3696
CHEVROLET COBALT S 2.2 / 4 E4E X $1440 1600 31 44 26 81 3840
CHEVROLET COBALT S 2.4 / 4 M5+ Z $1580 1580 30 46 24 79 3792
CHEVROLET COBALT S 2.4 / 4 E4E Z $1600 1600 30 44 29 88 3840
CHEVROLET COBALT (TURBO) S 2.0 / 4 M5+ Z $1620 1620 30 43 23 74 3888
For Comparison the Honda civics
Make/Model Class Eng Size/
# Cyl Trans #gears Fuel Consumption Rank CO2 kg per year
Type $/yr L/yr mi./gal. Class All
City Hwy
HONDA CIVIC S 1.8 / 4 M5+ X $1170 1300 38 52 5 14 3120
HONDA CIVIC S 1.8 / 4 E5E X $1278 1420 34 50 10 28 3408
HONDA CIVIC S 2.0 / 4 M6+ Z $1740 1740 28 42 36 165 4176
And the Mazda 3
Make/Model Class Eng Size/
# Cyl Trans #gears Fuel Consumption Rank CO2 kg per year
Type $/yr L/yr mi./gal. Class All
City Hwy
MAZDA MAZDA 3 C 2.0 / 4 M5+ X $1332 1480 34 46 10 39 3552
MAZDA MAZDA 3 C 2.0 / 4 S4+ X $1422 1580 31 44 22 78 3792
MAZDA MAZDA 3 C 2.3 / 4 M5+ X $1458 1620 31 42 25 93 3888
MAZDA MAZDA 3 C 2.3 / 4 S5+ X $1494 1660 30 41 32 117 3984
Based on the Government Testing the domestics are not as good as the Civic, but better then the mazda 3's on a consumption basis.
Because It is not clear that they are using Imperial gallons. I think most people who look at that ad. Will think that the cars do better gas mileage than they actually do. The Domestics are the worst when comes to gas mileage. Which is why they use those figures. Who to say what they intention are. I can only speculate.
I don't see how the add can be considered deceiving as the info is in agreement with the government published data. It has always been accepted by people of my generation that if you see a mileage published in a Canadian paper that it be in imperial unless it Clearly states US MPG They could also advertise the Impala As getting 40 MPG as that is the Highway mileage for one Impala Model. While the domestics have a Lot of things they need to improve ( I wouldn't own an Aveo if you gave it to me) Clearly fuel consumption is one area where they are making great improvement over a decade ago. When the Ford Focus gets a rating of 50 MPG while the Niisan versa gets a 47 mpg highway rating,(*Again from the NRC) then its time for you to reconsider such a sweeping statement as "The Domestics are the worst when comes to gas mileage"