Horrible gas mileage post DIY work; looking for help

I've been a long time lurker here but for the last three months I've really been depending on this forum.

I've got a situation with my 2006 4x4 DC SR5 V6 (117K miles) that I can't figure out and I'm hoping someone here will be able to help me with.

In the last three months I've performed the following:
Greased chassis
Changed fluids in rear, transfer and front (Mobile1 75w90 which includes the LSD addititive)
Replaced both of the front hub assemblies thanks to nj636 on the forum
Change air and cabin filters (OEM)
Changed spark plugs with OEM Denso
Cleaned PCV

This is more of a commuter vehicle than anything. No hard use. No customizations. No Check Engine Light or anything that would positively point to an issue.

...and my gas mileage has taken a 20% hit. I was, and have been, getting steady 19 +/- mpg for the seven years I've owned the truck. Even before I changed my plugs and with a bad wheel bearing I was getting a consist 19mpg and regardless of summer/winter fuel blends.

Now I'm getting 16ish mpg.

I'm aware of the 'winter' fuel but I think it's something more. Yesterday I was towing a very lite empty trailer and was having difficulty maintaining speed without getting in to the pedal a bit. It did feel like the engine was

I'm thinking this is something with the plugs, but aside from checking the connections, I do not know how to test to make sure they are all firing.

Is there anything I'm missing for a tune up or something that would be causing this sudden change in mileage. I plan to re-check the plugs today to make sure they are torqued correctly and the coils are seated.

On, and while I'm not familiar with the tasks above, I'm not the most mechanically inclined person you'll ever meet. If you do have a suggestion, please be very descriptive of the way to address it. I am; however, fairly good with my Google-Fu and haven't found anything good yet. So I'm turning to the crowd here.

Thanks ahead of time for any help!
-S

 

Plugs gapped to factory spec?

 

Yep, I used Chris4x4's thread here on the forum on changing the plugs and verified the gap on each plug before installation.

 

When was the last time you changed the fuel filter. Now I'm going to show my ignorance with even my truck...do they have plug wires...

 

I believe the fuel filter is non-serviceable and is part of the gas tank.

I'll check the wheels today. I thought of this but figured I would hear a rubbing/grinding noise. How do I check for a sticking caliper?

 

Fuel filter is non serviceable, aside from replacing the fuel pump. If your caliper is stuck the wheel that is on the same caliper will be extremely hot after driving it.

 

Short winter trips will kill your mileage don't know where you are but it has been zero or below here for a month or so and my mileage took a pretty big hit, warming it up when it's real cold beats on the mileage too get in it and go.

 

I have touch checked my disks after a ride in to work (25 miles each way) and did not feel any heat. I was actually trying to see if any new etching was occurring on the surface to see if a brake was dragging.

I'll check again today to see if I can feel any thing closer to the caliper.

 

May want to in hook your battery and wait 10-15 min to see if it will reset the ecu. Might need a new learning curve to go by. Worth a shot for no money.

 

[update] I just got back from church which is about a 15 minute drive. After arriving at church I touched the brake caliper and wheel/rim and both were cool to the touch. On the way home I filled up again and got slightly better with this last tank at 17.32mpg.

Thing is, when I got home I re-checked the caliper and wheel but this time touched the rotor disk surface. It immediately singed my finger tip. I should include it's roughly 1.5 miles through my neighbor to the drive way so I might hit the brakes a few time on the way in.

I don't get any shimmy or shaking when I brake or any pitching to one side or another.

Is this normal or does this point to the brake pad excessively riding the disk? If so, what corrective action should I take?

 

Perfectly normal. I do radio work on Mt. Washington there is a road to the top that people can drive and it is not unusual to see their rotors glowing red when they reach the bottom. Yes they do get hot but it only takes temps around 140* to cause burns. If you have any doubts about a dragging caliper the only real way is to jack it up and turn the wheel by hand they all drag slightly but if it takes some effort to turn the wheel it maybe be some thing to have a look at personally I doubt it is your issue. 17+ MPG in the winter and short trips is about all you are going to get.

 

Thanks for that info.

My current tank seems to be doing better and the hesitation hasn't reoccurred. I'm now wondering if all the DIY work wasn't a red herring for a bad tank of gas ...or two. The previous 4-5 tanks were all from the same service station. My last one was for a different location.