I just completed a 1000 mile round trip. On the way there I used the stock air filter with 5000 miles on it. I averaged 33.3 mpg according to the MID. Before I left to come back I installed a new K&N air filter. I averaged 31.8 mpg according to the MID. I was a little disappointed in the performance in the K&N. I made sure I set the cruise at 76 while on the highway. I also drove with the AC on recirculate.

I have had instant mpg gains with K&N air filters on other cars. Has anyone else noticed a drop in mileage with a K&N? Will mileage get better when it gets a little dirty?

 

Too many other factors to attribute it to the filter only (wind, temperature, traffic, topography, etc.) I thought as the filter gets dirty the engine works a little harder to suck the air in thereby decreasing mileage.

 

I put in a K/N filter in my 06 about 3-4,000 miles on the Odo. I really didn’t notice a change in mpgs (maybe a real slight extra growl at full throttle). I’ve notice a change when I started using Mobil 1 5w-30 at 5,000 miles, about an extra .4 to .7 gain on average mpgs.

Where I live, the elevation can change from a low of 4000 feet to a high of 8500 feet on road trips. I usually get better mpgs one way compared to coming back the same route. Plus, time of day (early morning or hot afternoon), slight head/tail/side winds, drafting behind other vehicles, and power used to pass other vehicles can influence mpgs.

Anything above 31 mpg with an average speed of 75 mph is a HUGE victory in my book.

 

I travelled the same roads (I-95 and I-10) there and back. I also travelled the same time of day and the ambient temp was about the same. I don't know about winds. I will keep monitoring it. I used Mobil 1 at my first oil change but, I don't know if it made a difference.

 

You may have used the same roads, but you were traveling in the opposite direction. If the general elevation was rising on your return trip as compared to your arrival leg, then the overall mileage will suffer because you will be attempting to fight gravity.

I have seen this with my extended drives to the New England area. Generally I get better fuel mileage going there than returning back to DC largely because I spend more time on a slight upward slope on the way back.

 

I started a sea level (Savannah, GA) and ended at sea level (Destin, FL).

 

If your route has any hills or mountains then it also makes a difference whether you climb them with a full tank or with it nearly empty.

 

What is the elevation above sea level of your starting and ending point? It's kind of silly but it will affect your mileage. If you are working up hill, your mileage will be less than if you are working down hill.

 

without more data this is pretty much speculation; I would say that 31.8 versus 33.3 is not statistically significant.

you should drive the complete run with one filter, and then swap and drive it again. repeat a few times. make sure you get the same gas from the same stations, and do your trips at roughly the same time of day.

then we can talk about the filter making a difference.

 

btw Destin is nice. Gotta love those white sand beaches. Hope traffic wasn't too bad around Jacksonville.

 

I drove down to Tampa this weekend to pick up a new toy and kept track of my mileage again. I got around 33.5mpg according to the MID going down and coming back. It was mostly interstate driving with some state highway driving. I am assuming that the ECU has adjusted to more air coming in and is running more efficiently now.