Bad MPG

Ok ive owned this car for about a year now. car has 110k on it. bought it with 94k the MPG meter is normally really close for the MPG. i noticed yesterday my Gas light came on and the car only had 270ish miles on it. so i thought the fuel gauge was inaccurate. I drove it until i had a tad over 300 miles on it and filled it. the car took 9.8 gallons. i was a tad shocked the MPG was showing 45ish mpg but when i did the math i had more like 33ish. i drove to work and back to the gas station i filled it up at exactly 50 miles as i rolled into the gas station. i filled it up and it took 1.4 gallons that's 35mpg the meter was showing 47mpg to me that's a huge difference if i was 1-3mpg i wouldn't even think much of it.... things to mention I had replaced the ABS unit 2 weeks ago 1300 for the part and a good tech installed it for me for another 250... i also at the time put on my brand new snow tires. stock size 15s firestone winter force tires.... I was wondering if there is anything else i need to reset or something i am over looking. any input would be great thanks

 

im sure my autel can test it. ill test it this weekend