Not sure which 2003 Mercury Grand Marquis Air Filters - Custom Fit is right for you? We have over 14143 customer reviews, with an average rating of 4.5, to help you find exactly what you're looking for. Here's what some of our customers have said:
"I purchased my K&N filter approximately 4 weeks ago and noticed an immediate increase in acceleration and gas mileage. Works great with the tornado air & fuel saver. Dyno tested approximately 42 more horsepower using both products. Base horsepower was 224 and now is 266. Gas mileage has improved approximately 7 miles per gallon; driving at the appropriate speed limit." —Robert D from White Plains, MD bought a K&N Air Filters for a 2003 Mercury Grand Marquis.