Just the K&N 77-2570KTK, otherwise all oem. The difference is hard to believe. We had a stiff crosswind all the way to Moab too.
For anyone familiar with the route from Vegas to Moab here’s some calculations from my gas receipts:
Hurricane UT to Moab UT 352 miles / 30.28 gal. = 11.624 mpg
Moab UT - Richfield UT 165 mi / 14.3 gal. = 11.538 mpg
Currently in Vegas , only 289 mi since topping off in Richfield. Will fill up again before leaving Nevada and update mpg for the last climb through 7700 ft driving west out of Utah.
Doing 67mph uphill in 3rd at 3200 rpm the scan gauge was showing 6.8 mpg. Before the transmission would typically downshift to 3rd at 2850 then to 2nd and struggle to hold 60mph at 3800 on steep grades. The outside temp was around 75. I was watching the water and transmission temps closely on the scangauge , both only increased 10 degrees on the long climbs.
I am going to do the opposite direction trip starting tommorow. My 2551 is an E450 with a higher numerical rear end ratio than the E350.
I already have a K&N filter but just the filter, not the intake setup.
With that, with the cc set at 68 and no serious head or tailwind... I average right about 10mpg.
I can get exact numbers for this trip.