Georgia FX4

First I just want to say this is not a how to get the most mileage out of my truck post.

I recently noticed that I'm not getting the same mileage out of my truck that I did 3-4k miles ago. As far as mods go, I put a set of Billstien 5100's all around set at 2.5" and a 3" rear block to keep my rake. I also have an Airaid CAI with 5Star Tunes and UPL catch can. Even after the lift, I lost maybe 1 mpg highway driving. Now I won't see better than 18 mpg at 65 mph with the cruise control on. My city mileage is significantly worse. I used to get 15-16 mpg city and now get 13.5-14.5 mpg.

I've cleaned the heck out of my MAF with MAF cleaner, get my oil changed every 5k miles, rotate my tires every 10k miles and keep them inflated to 40-42 psi. I also changed my spark plugs around 10k miles ago. As far as the tune that I run, its a 87 economy tune. I did run my 91 economy tune with 93 octane and saw a little better mileage but nothing to write home about. Is there anything I need to look at maintenance wise? There are no weird sounds, or hesitation or noticeable power loss.

stagalv

What engine do you have?

white08gt

check your frontend alignment

Abraham5G

I noticed my mileage decreased after my first oil change on my ecoboost. I also went from 20" to 22" wheels after my first oil change so that may have something to do with it.

ji603

You raised the profile of the truck, and increased the drag factor/wind resistance. You also changed the airflow with thr CAI and the computer will compensate with more fuel to match the increased air.

Of course mpg goes down.

Best config for mpg is factory spec, high psi in low rollling resistance street tires, and a very light foot, keeping the truck between 55-65. Anything else, you may gain performance, at the expense of fuel economy.

Idowa

On my 2012 Fusion, my tires say the max inflation is 52psi, and I kept them at around 50. with my K&N filter and custom exhaust, I averaged 34mpg on my daily 150 mile commute.

I got all of my oil changes done at the Ford dealer and after one change, noticed my mileage was dropping like a rock; maybe averaging 31mpg.

Checked my tire pressure and they had set it at 35 psi...

Filled the tires back to spec and mileage went back up...

On the other hand, in the Fall, the gas companies in more populated areas start switching to oxygenated fuel blends that will also cause around a 10% drop in gas mileage.

Usually I start noticing the difference in late September or October.

However, you said it's been going on the last 3k or 4k miles, so that can't be it...

How confident are you that the new plugs are still OK?

Georgia FX4

Sorry, I have the 5.0. Before I had the CAI installed when I first got the truck and was able to get really good mileage with it. I never noticed a big drop in mileage with the lift and don't see how slow city driving will affect it since the speeds I drive are under 40mph.

Project BLUE

I'm with you Georgia FX4. Before Bilsteins, solo exhaust and 5 star tunes I was hitting 18 mpg with long distances on hwy (with a CAI), fast forward with them on and another recent trip was mid to high 15's on the hwy. Granted I'm driving 75-80 on the hwy and have an ARE cap so I can't complain too much but to me the instant MPG is very inconsistent. Before any mods were done I was still never hitting above 18 mpg. I'm going to tinker with tire pressure next to see what will change there. Also did just fill up for the first time with 93 and loaded my 93 Perf tune so fingers crossed she treats me good.

SuperCruzin

With pressures that high on that application... you sir are a driving hazard to those around you.

Spec for your car is not 50psi. Spec for your car is 33psi. (the label is on one of your door jambs.)

But I do agree with you and looking at the spark plugs.

OP: I would pull your spark plugs, check them and re-gap them if necessary. Common issue on both the 5.0 and 3.5EB. Mine started missing at just over 30k. first thing I noticed was my mileage tanking. (before I ever even felt the miss - before any CEL) Regapped them, disconnected battery overnight, hooked it back up the next day and my mileage went back to normal. This evening on the way home, I stopped at a shell station just over 50 miles from my house, filled up with 87, then promptly averaged over 20mpg (dash calc - but its usually very close +/- .1mpg) for the 50 mile highway trip to my house. this was on a Super Crew 5.0 4x4 with 305/55R20 "E" Range tires, and a 2.5/1.25 level lift 3.73 gears. Engine stock from airbox (paper filter) to tailpipe. NO tuner.

If you take us up on our advise... Use a wire gauge, not a ramp (ramps are notoriously inaccurate) .045 seems to work well (for me). Torque to 15ft/lbs and apply dielectric grease liberally to the inside of the CP boots.

Idowa

They were the Michelin Energy Saver A/S in 225/50/17 with a max inflation pressure of 51psi.

I drove on those tires at around 50psi for 72k miles from Phoenix, AZ to Prescott, AZ 5 days a week for 2 years.

I drove in blizzards, monsoons, and on 120 degree days without a single incident and got 72k miles out of those tires.

I now run a set of Cooper Zeon RS3-As which have a max inflation of 50psi. Went through last winter with zero issues running a more conservative 40psi.

Yes; the door jamb pressure is the recommended pressure to use based upon the vehicle weight and is to provide a balance between wear, ride, mileage, and grip. It is usually very, very conservative...

However, every tire is designed differently and some can easily be inflated to max pressure without adverse affects; as witnessed by my Michelins. I checked a couple of hyper-miler sites about running higher tire pressures and the Michelins were one of the brands that preform just fine at high pressures.