No joke my 155 did return 35-37 mpg.
Spec was:- 1996 155 2.0 16v sportpack, gas-flowed head, fast road cams, full supersprint exhaust (no cat), K&N panel filter, uprated & lowered suspension, drilled discs, braided brake lines, motorsport alloys,Blah, blah, blah... It had over £6000 of mods and was reasonably quick. In 1999 I filled up with unleaded at home (20 miles north of Dundee) and reset the trip meter then headed down south, followed by a 1998 Nissan Almera 1.4 who also filled up and reset his trip meter. After numerous blasts at over 100 (one was an indicated 142, and still pulling (downhill)) and then several cruises waiting on the Almera, i got a call from the Almera who had just noticed he was thirsty, we stopped at the next service station and filled up (343 miles later on the 155, 347 on the Almera)), the 155 took just over 1 litre LESS than the Almera, and averaged 37.3 mpg and still had about 1/4 of a tank left.
The 155 had 86,000 miles on it, but is now about 3 foot shorter due to some dumb B**ch broadsiding her Astra into the front of it in the snow.
I should note that if I was driving it hard without cruising the mpg would be in the low 20's if that!