Excessive fuel consumption Audi S5
 

Hello, since I changed my spark plugs (Denso # 5304 IRIDIUM Power IK20
for (NGK PFR6W-TG (5547) LASER PLATINUM SPARK PLUG)
my car (Audi S5 2011 4.2l) consumes more gasoline and less power. I checked the gap (0.036'') before installing them.
On the fuel consumption indicator when it changes from 10km it make 6km on the conter.
Someone can help me?