Fuel Milage Drop

[Danweis1]

Hello,
2016 Ram 1500 Big Horn, 5.7, 160,000 miles.
Recently installed new plugs. My previous average milage was 17.1 over many months of mostly rural driving. Truck runs great and I have not noticed any difference in power, acceleration, etc. Does seem to run a little smoother. HOWEVER my milage has dropped down to 14.8 over several hundred miles, driving the same routes, etc. The replacement plugs were the exact same brand and model I removed. I’m completely baffled by this. I did have the battery disconnected because I had to replace it. Did the computer reset maybe? Anyone have any thoughts on this?
Thanks

 

[Wild one]

Hello,
2016 Ram 1500 Big Horn, 5.7, 160,000 miles.
Recently installed new plugs. My previous average milage was 17.1 over many months of mostly rural driving. Truck runs great and I have not noticed any difference in power, acceleration, etc. Does seem to run a little smoother. HOWEVER my milage has dropped down to 14.8 over several hundred miles, driving the same routes, etc. The replacement plugs were the exact same brand and model I removed. I’m completely baffled by this. I did have the battery disconnected because I had to replace it. Did the computer reset maybe? Anyone have any thoughts on this?
Thanks

Where did you get the plugs from? Ebay and Amazon are flooded with Chinese knock off NGK's

 

[Sherman Bird]

Hello,
2016 Ram 1500 Big Horn, 5.7, 160,000 miles.
Recently installed new plugs. My previous average milage was 17.1 over many months of mostly rural driving. Truck runs great and I have not noticed any difference in power, acceleration, etc. Does seem to run a little smoother. HOWEVER my milage has dropped down to 14.8 over several hundred miles, driving the same routes, etc. The replacement plugs were the exact same brand and model I removed. I’m completely baffled by this. I did have the battery disconnected because I had to replace it. Did the computer reset maybe? Anyone have any thoughts on this?
Thanks

 

[Danweis1]

Well it looks like I probably shot myself in the foot. I dug the old plugs and the new plug boxes out of the trash and realized they were not the same. The plugs I put in were NGK LFRAIX-11. The ones I took out were NGK LZFR5CI-11. I don’t immediately know what the difference is but it sure affected my milage. Most likely another plug change coming up….
Thanks for your responses.

 

[Wild one]

Well it looks like I probably shot myself in the foot. I dug the old plugs and the new plug boxes out of the trash and realized they were not the same. The plugs I put in were NGK LFRAIX-11. The ones I took out were NGK LZFR5CI-11. I don’t immediately know what the difference is but it sure affected my milage. Most likely another plug change coming up….
Thanks for your responses.

Do not buy NGK's off Amazon or Ebay,if you do another plug change.Google fake NGK plugs on Amazon/Ebay,they're one of the most common brands to be Chinese knock-offs

 

[Danweis1]

Do not buy NGK's off Amazon or Ebay,if you do another plug change.Google fake NGK plugs on Amazon/Ebay,they're one of the most common brands to be Chinese knock-offs

Getting them from Rock Auto this time….

 

[CunningStunt]

Getting them from Rock Auto this time….

also, check the gap on all of them. With 16 of em, theres bound to be one bad. .044

 

[CunningStunt]

Hello,
2016 Ram 1500 Big Horn, 5.7, 160,000 miles.
Recently installed new plugs. My previous average milage was 17.1 over many months of mostly rural driving. Truck runs great and I have not noticed any difference in power, acceleration, etc. Does seem to run a little smoother. HOWEVER my milage has dropped down to 14.8 over several hundred miles, driving the same routes, etc. The replacement plugs were the exact same brand and model I removed. I’m completely baffled by this. I did have the battery disconnected because I had to replace it. Did the computer reset maybe? Anyone have any thoughts on this?
Thanks

Also if you have a scanner check for some codes. When my lifter failed fuel mileage dropped to about 14-15 over my normal 18-20.

 

[Danweis1]

Thanks, will do.

 

[htwo]

Mileage drop can be unrelated to plugs. New fluids all around can help - synthetic fluid can 'free up' HP that is often lost due to friction. Brakes might be dragging a bit; poor alignment can affect things; different tires can affect .ileage depending on tread pattern, etc. I often carry a few hundred pounds of tools in the back seat, I had to carry more for other odd jobs and noticed a slight drop in mileage. I run LT tires, did a mulch job for a client and left the tires at 60psi and the 1/4" ride height threw the speedometer off enough that my GPS calculated a 6% difference in distance and based on fuel use that can make a difference as well in hand calculated mpg.

 

[Sherman Bird]

Mileage drop can be unrelated to plugs. New fluids all around can help - synthetic fluid can 'free up' HP that is often lost due to friction. Brakes might be dragging a bit; poor alignment can affect things; different tires can affect .ileage depending on tread pattern, etc. I often carry a few hundred pounds of tools in the back seat, I had to carry more for other odd jobs and noticed a slight drop in mileage. I run LT tires, did a mulch job for a client and left the tires at 60psi and the 1/4" ride height threw the speedometer off enough that my GPS calculated a 6% difference in distance and based on fuel use that can make a difference as well in hand calculated mpg.

I had a customer with a 2011 Ford Fusion 2.5L engine. The car got about 30 MPG when new. At about 20,000 miles, she began complaining about a drop to 21-ish MPG.... quite a drop. The car ran fine... Problem turned out to be a "bad" battery, capacitance wise. Although it started and ran the car, the computers weren't able to function up to par.
We replaced the battery, and the car got over 30 MPG once again.

 

[Danweis1]

Replaced the plugs (again) with plugs from Rock Auto. Although I haven’t driven enough to be sure, it seems the Milage has improved significantly. It’s current at 16.8, which is far better than it was.

Comments on others advice; I am running 100% synthetic oil; new oil 3 months ago. My battery is new. My truck runs empty 98% of the time. I keep my stock tires at 42-43 psi (38 psi is what’s recommended on the door sticker). I hand calculate my milage always. It agrees with the computer within +- 1 mpg. Scanner shows no codes.

Thanks for everybody’s input.
Cheers

 

[Jwithing]

One thing to call out that I just did and made a difference for me after 35k miles... Three back to back treatments of Red Line SI-1. I had changed plugs, wires, injectors, battery, sensors, and checked for play in the lifters. None of it made a huge difference and I would get intermittent misfire codes randomly. The SI-1 finally did the trick and I noticed mpg change after 1.5 treatments.

 

[Wild one]

Merely disconnecting the battery will NOT reset fuel mapping in long term memory. IF you take a 10 ohm resistor and wire it across the positive and negative battery cables. WITH BOTH CABLES DISCONNECTED FROM THE BATTERY.... and leave it for about 20 minutes, the gates will reset back to factory default.

Wouldn't stepping on the brake pedal with the battery disconnected accomplish the same thing.Both drain the system

 

[Hagar1]

Wouldn't stepping on the brake pedal with the battery disconnected accomplish the same thing.Both drain the system

Depending upon year, some of the later model vehicles need "key" on in order to allow brake lights to illuminate. That is the way my 2012 is and I checked into it and was told , "that is the way it is now."

 

[Wild one]

Depending upon year, some of the later model vehicles need "key" on in order to allow brake lights to illuminate. That is the way my 2012 is and I checked into it and was told , "that is the way it is now."

Something wrong with your truck then,as all 3 of my Chryco's turn on the brake lights with-out the key on,as far as i thought,it's the law to still have brake lights with-out the engine running