Sudden reduction in MPG

[chrisfc923]

So all of a sudden I've noticed a huge MPG reduction. I've always averaged about 16.5mpg. About a month ago I installed the BMS tuner and it dropped to around 16.2ish but I chalked that up to maybe me being more aggressive with the tune. Then all of a sudden after I would say 300miles, I noticed the comp reading I'm getting 13.5mpg. Just by going off of the mileage compared to my gas consumption I knew something was up. I thought maybe it was the chip so I disconnected it and have now driven about 50 miles. I'm still showing only about 14mpg. Any idea what could of caused this?

[LatinBimmer]

IMHO, the more power you add, the more gas you need....it's like moving between driving modes: ECO, Comfort and Sport...maybe now that you disconnected the chip, the engine needs a while to restore to its settings?

[Blackhawks]

Summertime gas has additives to appease the EPA. Don't discount that, either...

[onfireX5]

Did the interstate only mpg drop also ?

[42pilot]

My recommendation is that you keep the chip disconnected and run a full tank of gas, and figure the mpg the old-fashioned way. My computer is always 2 mpg too high and sometimes more than that.