Didn't really know what to expect. I just bought a 2010 xlt sup cab 4x4 5.4 with 80k miles yesterday(Friday). The previous owner told me not to expect more thany 17MPG and his average was 16.7mpg. I wasn't to thrilled about that. He drove it 90 Rt each day to work. Anyways, I picked the truck up and had my friend follow me 64 miles back home, then 64 miles to take him back and again 64 miles home(finally). Anyways, I reset the MPG on the CPU and was quite amazed. I drove like my grandma(60MPH) and tried to coast a lot. I made 1 stop for gas, 2 stops for pizza and numerous small 3 stoplight towns on the journey. Over about 300 miles I averavged 22.4.

Sidenote: I finally found how to get the air filter box off to check the filter(didn't want to break anything last night). The filter is definately in need of being changed. I hope between a new filter, changing over to castro syntec I might get even better mileage. Not sure if I will use a K&N filter as I am not quite sold on them(used 2 in other vehicles without any significant gains(BoxsterS and Infiniti FX35).

 

Speaking of air filters... I know they are supposed to help with mpg's with more air flow, but I'm kind of worried how well it will filter the dust filled air I usually drive through (so bad sometimes you can't see 10' in front of you). As it is I usually have to replace it every 6-8 months.

 

This is amazing. I had 2 2003 5.4 half ton, 2 wheel drive. I never saw 17 MPG average on a tank full, even on a trip, of coarse on the interstate I drive 75 or so, found if you don't you get run over! I suppose at 60 they may of done better. Around town, stop and go?? 14-15 tops. Loved the trucks but hated the mileage. I think if you read the comparison specs on K&N filters compared to stock you will see the K&N collects dust better. It will depend on the quality of the stock air intake and filter, some are much better than others. I will say though, depending on vehicle, don't expect a lot better mileage. The big plus to the K&N is you almost never have to change them, just clean them. For my truck, I'd never buy another one, biggest differance is it sounds better!! JMO.

 

I equate my 22.4 MPG to a couple factors. Driving "gingerly", 6spd tranny, and keeping it under or at 60mph. I am now at 21.6 with a little "light" city driving. The hardest thing on mpg is getting the big beast moving!!

As for K&N, I am done with marketing hype. I have seen it in about all forms over the years. First it was Slick 50, now it is what motor oil do I use(dino or synthetic/5W20vs5W30Vs???). Actually if you leave your beast stock and use factory recommended MC oil ... here is the key... You change it often(5k is my rule), your vehicle will love you and last for you!!

 

Update us when you can hand calculate it as I find the readout on my 09 5.4 is a bit off. I know I can get good mileage out of mine but we have too many hills, a lot of wind here and mine is extra heavy from tools. Mine is nearly identical to yours but an 09 (or it was before mods). I did get about 15-16 going 80 all the way back from MN though so I'd call that pretty decent.

 

I have only tried synthetic oil once a long time ago in a 99 with 75000 miles on it. The truck never used any oil bu with synthetic it did use a qt about every 2000 miles. Slick 50? It has been proven to me it does extend engine life. Yes driving 60 as opposed to 80 on the interstate, like i do will increase your mileage a great deal, but it takes a special person to be able to do that! LOL

 

I use the onboard MGP calculator as a comparison to what the previous owner was getting rather than the law. I will be using paper and pencil once I get my second fillup and on. I don't have any interstates in my daily driving so keeping it under 60mph is pretty easy on my 55mph roads.

I don't do any oil analysis so I can't say with 100% accuracy either way what all the oil additives really do. I am going to adhere to the old rule... If it aint broke, don't fix it

 

If oil additives worked, then they would come already in the oil. Each oil already has an additive package specifically engineered to work a certain way.

 

as for my K & N air filter (2013 F150, 4x4, 5.0, 3.55 gear) I saw no change in mileage.
I have many repeat trips to the same place/route, 400 mile run. some 70MPH and mostly 60-65MPH average has been 20.7. keep it slower and I will get 21.5. Don't give a care about mileage 19.5

 

I have the same truck and I drive 100 miles a day on rolling hills to work and I get a pretty consistent 17.8 to 18.2 at 65mph.