bad fuel mileage on 2001 Dodge Grand Caravan

I have a 01 grand caravan with 3.8 AWD and I am get about 14.5 miles per gallon highway. it has an 06 motor I got the same milage on the old motor also get codes 0172 and 0455.

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1 answer
The P0172 code is for a rich running condition and the P0455 is from a leak in the evaporative system. The P0172 code is the one that will effect the fuel economy and the diagnostic procedures related to that code need to be performed.