mileage slump

[dchamb9414]

my '02 is giving me 50 miles less per tank over the last few months. the shop put the computer reader on and got no codes, so they think i don't know what i am talking about. Who this day and age doesn't keep close watch on mileage? the only other symptom is a minor tremor on the steering wheel when idling. anyone have any thoughts on this? some say etyhonol (sp) causes this, but weve had that stuff a long time now.