Was stuck in traffic right next to ORD(i know amazing) A Lufthansa flight was landing almost right over me as much as I can determine it was flt DLH432. I had to do a double take as it appeared the plane a 767 had two different engines??? I have experience working as a ramp supervisor for an air freight company so as I said i have never seen anything but an experimental aircraft with different styles of engines. The only reason it was noticeable was the #1 engine was a engine with the large cowling and #2 looked like a normal engine. And as I said I was able to get a good look at the aircraft.
Lufthansa does not even have 767’s to my knowledge. What you saw was most likely an A330 and I assure you they have the same engines. 
Could have been different colored cowlings if they had to stick a spare into service without repainting. One in standard gray and one in black or white or something that looked bigger/smaller.