I found this on links on this forum.
The AMG video claims 6.9 l/100 km highway
The CLA250 data below claims 4.9litre/100 km highway (48MPG)
Obviously these are not the numbers that would be published in the US Fuel Efficiency guide, but perhaps thy show that the CLA250 would get 40% better highway mileage than the CLA45
MERCEDES BENZ CLA (C117) CLA 250 (211 HP) (2013 - PRESENT) DIMENSIONS, GROUND CLEARANCE, FUEL, ACCELERATION
GENERAL
CYLINDERS
4
DISPLACEMENT
1991 cm3
POWER
155 KW @ 5500 RPM
211 HP @ 5500 RPM
208 BHP @ 5500 RPM
TORQUE
258 lb-ft @ 1200-4000 RPM
350 Nm @ 1200-4000 RPM
FUEL SYSTEM
Direct Injection
FUEL
Petrol
CO2 EMISSIONS
142-144 g/km
PERFORMANCE
TOP SPEED
149 mph OR 240 km/h
ACCELERATION 0-62 MPH (0-100 KPH)
6.7 s
FUEL CONSUMPTION
CITY
28 mpg US OR 8.4 L/100Km
HIGHWAY
48 mpg US OR 4.9 L/100Km
COMBINED
37.9 mpg US OR 6.2 L/100Km
TRANSMISSION
DRIVE TYPE
Front Wheel Drive
GEARBOX
7G-DCT dual-clutch automatic transmission
BRAKES
FRONT
Ventilated Discs
REAR
Solid Discs
TIRES
TIRE SIZE
225/45 R 17
DIMENSIONS
LENGTH
182.3 in OR 4630 mm
WIDTH
70 in OR 1778 mm
HEIGHT
56.6 in OR 1438 mm
FRONT/REAR TRACK
60.7/60.7 in OR 1,542/1,542 mm
WHEELBASE
106.3 in OR 2700 mm
GROUND CLEARANCE
3.9 in OR 99 mm
CARGO VOLUME
16.6 cuFT OR 470 L
CD
0.28
WEIGHT
UNLADEN WEIGHT
3263 lbs OR 1480 kg
GROSS WEIGHT LIMIT
4332 lbs OR 1965 kg