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Discussion Starter · #1 ·
Hi everyone, my mileage has dropped off lately and I don't know why. I thought I'd ask all the Titan fans on here and see if anyone has some insight.

2006 SE 4x4 king cab, 176000 km. I regularly get 330km on the top half of the tank and another 150 before the gas light comes on. Always, for the last 5 years, driven hard or babied, it's all the same.

Lately I get about 260km on the top half. I don't know what changed. I got new tires and had the rear brakes done. The new tires are a little more aggressive than the last set, but not off-road tires or anything. I doubt that would be it. I went back to the shop to see if the brakes were dragging or something but they say it's all good.

I put in new plugs last weekend to see if that would help but it made no difference. My driving patterns have not changed at all either. I fuel up all over the place, so it wasn't a bad tank of gas. Why would I suddenly get such poor mileage?

What do I try next? A mechanic suggested my O2 sensor might be out of spec and is causing a rich mixture...haven't looked into it yet. Power and performance seems good.

Any ideas?
 

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tires do make a difference in gas milage
 

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Discussion Starter · #3 ·
I know tires can make a difference, but that big of a difference? Seems unlikely. Went from Goodyear SR-A to Cooper Discoverer H/T. Proper pressure maintained.
 

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You sure your fuel sending unit isn't bad and saying you have less gas than you really do?
 

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Yes, there is a fuel sending unit recall on the 06's.
 

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If i'm not mistaken even the new sending unit go bad. How many gallons or liters of gas are you putting in it and whats the gauge reading before you fill up?
 

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Check the weight difference between the old tires and the new ones. Those Goodyears are what they put on stock and tend to be light. Also, if you put on bigger tires than the stock ones, then that will drop your mileage. Even if they're just a little bigger (a width increase especially), that would mean a drop. Tires can definitely make a difference. Could be that combined with something as simple as a dirty air filter. It doesn't take much to drop the mileage on these trucks.
 

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I have heard a manifold leak can cause gas mileage to suffer.
 

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^^^ It can. That and having manifolds altogether. When I changed from leaky manifolds over to Thorley LT's, I gained about 2mpg.
 

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I'd trust my odometer before by fuel gauge, odometer can be checked against mile marker posts, are you checking your miles driven against the gallons/liters to fill it up?
 

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Maybe someone drilled a hole in your gas tank and is stealing gas from you every night. It happened to a guy on the forum. SomeOne drilled a hole in his tank and put a rubber plug, the guy would fill up his truck,come home and at night a person would crawl under his truck, remove the plug and drain his gas into a jerry can. Just a thought.
 

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Hi everyone, my mileage has dropped off lately and I don't know why. I thought I'd ask all the Titan fans on here and see if anyone has some insight.

2006 SE 4x4 king cab, 176000 km. I regularly get 330km on the top half of the tank and another 150 before the gas light comes on. Always, for the last 5 years, driven hard or babied, it's all the same.

Lately I get about 260km on the top half. I don't know what changed. I got new tires and had the rear brakes done. The new tires are a little more aggressive than the last set, but not off-road tires or anything. I doubt that would be it. I went back to the shop to see if the brakes were dragging or something but they say it's all good.

I put in new plugs last weekend to see if that would help but it made no difference. My driving patterns have not changed at all either. I fuel up all over the place, so it wasn't a bad tank of gas. Why would I suddenly get such poor mileage?

What do I try next? A mechanic suggested my O2 sensor might be out of spec and is causing a rich mixture...haven't looked into it yet. Power and performance seems good.

Any ideas?

They may not have adjusted your brake adjuster in the rear hubs causing them to 'drag'.... Jack the back of the truck off the ground by the axle, preferably place it on level surface and wheel chock the front wheels. Jack the axle up with the tranns in neutral, spin the tires, if they hardly move you need to pull the hubs and have the adjustors spun all the way in.
 

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I have heard a manifold leak can cause gas mileage to suffer.
I was getting 11 - 12 before my manifolds were replaced and getting 12 - 12.5 after. Not really that big of a deal and personally I think getting summer gas and the warmer temps are more to help than the manifolds.
 
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First thing to check is the coolant temperature. Thermostats go bad right about this mileage/time point and they are subtle stealers of fuel mileage. Typically it's a soft failure, not enough to set an engine code. Some vehicles allow you to read temp directly from a scan tool. If it's on the cold side of normal, you have your culprit.

Easy check: how has your heater been working lately? Wimpy output? Go for the 'stat. Get the hottest one you can get for the truck and the mileage will perk up.

It used to be an old hot-rodder's trick to put a really cold stat in an engine to make it make better horsepower, but your gas mileage really suffers. I did it to my Barracuda and was able to keep up with a guy with an SS396. And boy was he mad...
 

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Discussion Starter · #19 ·
Thanks everyone for all the suggestions.

The wheels spin free, not the brakes.

Had the manifolds replaced once already at about 150000. I could hear them leaking, just like my last Nissan, and the one before, and the other one before. I can't hear the new ones leaking...yet. I think they are ok.

Temperature seems normal.

Power also seems normal.

Air filter is clean. Fuel filter not checked yet.

I have had all recalls taken care of (and there have been a lot!) except for the ECU relay, which I believe would have affected me by now if it was going to.

I did have to rewire my rear door harnesses after the crappy dealer fix didn't work and the wires all snapped on a very cold day, shorting out the stereo and messing up the belt tensioner. Maybe that's the issue LOL.

I also now have $600 worth of brand new power steering high pressure and return lines after they exploded recently.

Powertrain is still running strong but with the price of fuel lately I want to get her a little more efficient. The new Ford 3.5L is starting to sound appealing!
 

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I have had all recalls taken care of (and there have been a lot!) except for the ECU relay, which I believe would have affected me by now if it was going to.
The ECU relay can fail at any time, not just before a certain number of miles etc. There's been people that had it fail with <50k and I'm sure there's been people who have had it fail with >150k. The old relay is a bad design and most likely will eventually fail, it's just a matter of when and where. I know I wouldn't wanna be stranded away from home because of a $3 part that only takes the dealership 10 mins to swap out. Just giving you a heads up.
 
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