Poor MPG with new plugs

11123 Views 23 Replies 10 Participants Last post by BigPhatPaulie, Aug 9, 2018

jordan.twete

Discussion Starter · Apr 25, 2017 (Edited)

Hello all, I have a 2013 model f150 ecoboost that I have recently purchased a couple weeks back and had the dreaded miss that is ever so common. I ended up replacing my plugs and boots with Autolite XP5363 (gapped at .030) and Napa brand plug boots because I didn't want to spend the $$ on Motorcraft SP534 plugs which ran about 15 bucks a piece at my local dealer. My miss went away and power seemed to improve a bit but now I am averaging 13 mpg combined and about 14.5 on the interstate at about 75-80 mph. This isn't terrible compared to my GMC i traded in which was pretty comparable but I know many people with the same truck getting around 16mpg avg and 18-20 on the highway. If anyone could give some advice it would be much appreciated. Im thinking about just buying SP534s and throwing those in..

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parkerbill

· #2 · Apr 25, 2017

I just ordered Motocraft SP-534 plugs off Amazon for $7.22 each. One place had them for $5.21, but when I tried to set the quantity at 6 I got a message saying they were limited to one per order???? I also ordered new boots. My '13 3.5 EB has just under 44K miles on it and runs great, but we tow a travel trailer and are taking it on a two month+ trip to Alaska in June, so I figured I should maximize my towing mpg as much as possible.

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Mulyhuntr

· #3 · Apr 25, 2017

jordan.twete said:
Hello all, I have a 2013 model f150 ecoboost that I have recently purchased a couple weeks back and had the dreaded miss that is ever so common. I ended up replacing my plugs and boots with Autolite XP5363 (gapped at .030) and Napa brand plug boots because I didn't want to spend the $$ on Motorcraft SP534 plugs which ran about 15 bucks a piece at my local dealer. My miss went away and power seemed to improve a bit but now I am averaging 13 mpg combined and about 14.5 on the interstate at about 75-80 mph. This isn't terrible compared to my GMC i traded in which was pretty comparable but I know many people with the same truck getting around 16mpg avg and 18-20 on the highway. If anyone could give some advice it would be much appreciated. Im thinking about just buying SP534s and throwing those in..

You haven't supplied enough information to know if that is bad mileage for your specific truck or not.
-mileage before plug change?
-specs on truck? tire size, wheelbase, gearing, 2 or 4wd, etc.

75-80 mph on the highway will always net lower than desired mileage. I'd say 14.5 is about right at that speed if you are 4x4 with 3.73 gearing.

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MAXXPAY

· #4 · Apr 25, 2017

Mulyhuntr said:
You haven't supplied enough information to know if that is bad mileage for your specific truck or not.
-mileage before plug change?
-specs on truck? tire size, wheelbase, gearing, 2 or 4wd, etc.

75-80 mph on the highway will always net lower than desired mileage. I'd say 14.5 is about right at that speed if you are 4x4 with 3.73 gearing.

Bingo, this is my truck's avg at those speeds and the same specs you just mentioned, although I'm leveled with a topper. BTW this is with a stock tune. I am about 15.5 at those speeds with a tune.

jordan.twete

Discussion Starter · #5 · Apr 26, 2017

Mulyhuntr said:
You haven't supplied enough information to know if that is bad mileage for your specific truck or not.
-mileage before plug change?
-specs on truck? tire size, wheelbase, gearing, 2 or 4wd, etc.

75-80 mph on the highway will always net lower than desired mileage. I'd say 14.5 is about right at that speed if you are 4x4 with 3.73 gearing.

I changed the plugs at 75k miles, it is a 4x4 fx4 model w/ 3.55s supercrew with 5ft box whichever wheelbase that is i cant remember and 265/70/18 highway tires (not 100% on that size cant remember off hand). Do you think it would still be worth changing out plugs for the sp534s? Some people have said that those cheaper plugs like the Autolites can't handle the high cylinder pressures in the ecoboost, that being said most of them worked at ford dealerships and will recommend anything with the motorcraft branding.

dnellans

· #6 · Apr 26, 2017

It doubt its your plugs but something is definitely crappy with those MPGs. I've got a 2013 4x4 w 3.55 supercrew just like you and rolling on 265/75r20's which are even bigger then yours and i'm getting much better milage. 15-ish around town and 20 on pure highway (never really over 75 and usually 70) for average of 16.1 over life i've owned the truck, you definitely should be doing better. fuelly.com is your friend for understanding what people actually get for milage in these things

jordan.twete

Discussion Starter · #7 · Apr 26, 2017

What tune are you running in your truck? Im looking for a decently priced 87 octane tune that will give me a moderate bump in power and increased mpg as you mentioned. Ive seen some achieving over 80hp and 100 ft-lb torque in a tune like Livernois but I don't care to make any other mods to keep up with that much power as this is just my daily driver.

ptown said:
Bingo, this is my truck's avg at those speeds and the same specs you just mentioned, although I'm leveled with a topper. BTW this is with a stock tune. I am about 15.5 at those speeds with a tune.

MAXXPAY

· #8 · Apr 26, 2017

jordan.twete said:
What tune are you running in your truck? Im looking for a decently priced 87 octane tune that will give me a moderate bump in power and increased mpg as you mentioned. Ive seen some achieving over 80hp and 100 ft-lb torque in a tune like Livernois but I don't care to make any other mods to keep up with that much power as this is just my daily driver.

This is with a MPT, but I haven't had time to recheck it with Torrie's tune. I expect his to be the same or slightly better.

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MAXXPAY

· #9 · Apr 26, 2017

dnellans said:
It doubt its your plugs but something is definitely crappy with those MPGs. I've got a 2013 4x4 w 3.55 supercrew just like you and rolling on 265/75r20's which are even bigger then yours and i'm getting much better milage. 15-ish around town and 20 on pure highway (never really over 75 and usually 70) for average of 16.1 over life i've owned the truck, you definitely should be doing better. fuelly.com is your friend for understanding what people actually get for milage in these things

Speed has a pretty big impact on these trucks especially above 70, as that's when we start getting the RPM's up and making more boost

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Elmore328

· #10 · Apr 26, 2017

jordan.twete said:
I changed the plugs at 75k miles, it is a 4x4 fx4 model w/ 3.55s supercrew with 5ft box whichever wheelbase that is i cant remember and 265/70/18 highway tires (not 100% on that size cant remember off hand). Do you think it would still be worth changing out plugs for the sp534s? Some people have said that those cheaper plugs like the Autolites can't handle the high cylinder pressures in the ecoboost, that being said most of them worked at ford dealerships and will recommend anything with the motorcraft branding.

Before spending more money on the SP534's (like you should have purchased in the first place.

), I would do a KAM reset, allow the truck 50-75 miles of driving afterwards, and then recheck your mpg's. I wouldn't be surprised if your truck is trying to "relearn" with the new plugs and is costing you some precious mileage.

milesej05

· #11 · Apr 26, 2017

Go on eBay or RockAuto.com (supporting vendor) and buy the stock Motorcraft Plugs. I found a deal a while back from Pep Boys for a set of 6 it was only $27 dollars (with the discounts they were offering) so I ordered a dozen plugs.

Next thing is to do a KAM reset after changing plugs out. Also, UNHOOK YOUR BATTERY WHEN WORKING WITH THE ELECTRICAL SYSTEM OF YOUR TRUCK!!!

Wait a tank of gas before reporting back that your mileage dropped...your truck has to have time to 're-learn'

parkerbill

· #12 · Apr 26, 2017

Question: Why is it necessary to unhook the battery and do a KAM reset when changing the plugs in an Ecoboost?

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milesej05

· #13 · Apr 26, 2017

parkerbill said:
Question: Why is it necessary to unhook the battery and do a KAM reset when changing the plugs in an Ecoboost?

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KAM (Keep Alive Memory) is sort of like a restart of your home computer. Hypothetically, like on your computer, it clears all your RAM and starts over.

Unhooking the battery is kind of a common sense thing. You are working with electricity and if you have a probability of grounding out something while under the hood.

2012Lariat4x4

· #14 · Apr 26, 2017

KAM reset and drive at 60 mpg a see what happens. Even with 33x12.5 I can get 17.5mpg . go to 70 mph and it drops to 15mpg on the same road/trip . (my moms house was the test one weekend).

Have you replaced the $8 air filter?

parkerbill

· #15 · Apr 26, 2017

milesej05 said:
KAM (Keep Alive Memory) is sort of like a restart of your home computer. Hypothetically, like on your computer, it clears all your RAM and starts over.

Unhooking the battery is kind of a common sense thing. You are working with electricity and if you have a probability of grounding out something while under the hood.

I understand the battery thing. It's just a safety precaution in case you drop a wrench or something and it grounds a hot wire. But I still do not understand the need for the KAM reset. Why do you need to reboot the computer for a spark plug change? I watched several YouTube videos on changing the plugs on an Ecoboost and none of them mentioned a KAM reset. Please do not misunderstand; I am not arguing the point. I am only trying to understand the reason for it. What is gained, etc.?

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milesej05

· #16 · Apr 26, 2017

parkerbill said:
I understand the battery thing. It's just a safety precaution in case you drop a wrench or something and it grounds a hot wire. But I still do not understand the need for the KAM reset. Why do you need to reboot the computer for a spark plug change? I watched several YouTube videos on changing the plugs on an Ecoboost and none of them mentioned a KAM reset. Please do not misunderstand; I am not arguing the point. I am only trying to understand the reason for it. What is gained, etc.?

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To keep it short, it resets the computer. Everytime you load a new tune the device automatically does a KAM reset. Some people even do a KAM reset once a month. Everytime I get done towing my boat around I do it because your truck learns the shift points, etc.

Mulyhuntr

· #17 · Apr 26, 2017

Pepboys online has sp534's for 5.99. Order online and pick up in store.

Elmore328

· #18 · Apr 26, 2017

parkerbill said:
I understand the battery thing. It's just a safety precaution in case you drop a wrench or something and it grounds a hot wire. But I still do not understand the need for the KAM reset. Why do you need to reboot the computer for a spark plug change? I watched several YouTube videos on changing the plugs on an Ecoboost and none of them mentioned a KAM reset. Please do not misunderstand; I am not arguing the point. I am only trying to understand the reason for it. What is gained, etc.?

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With every ignition cycle the electrodes warm up and cool down repeatedly, and over time this is what widens the gap. As the gap widens the computer makes adjustments to the ignition cycle to compensate for the change in gap.
Then when you finally change plugs to new ones with the correct gap, the computer will still be firing as if the old plugs were in there and it can cause some rough idle, poor performance, loss in mileage, etc. In this instance, doing a KAM reset will start the learning cycle all over again, allowing the computer to adjust the parameters quicker and easier.

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parkerbill

· #19 · Apr 26, 2017

So, just to be clear my '13 3.5 EB is totally stock—no tuner. Should I still do a KAM reset after replacing the plugs?

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Elmore328

· #20 · Apr 26, 2017 (Edited)

parkerbill said:
So, just to be clear my '13 3.5 EB is totally stock—no tuner. Should I still do a KAM reset after replacing the plugs?

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In my opinion, Absolutely Yes...unless you want to deal with the possibility of your truck running different for up to 500 miles while it gradually relearns the new changes by itself.

edit: However, if your old plugs aren't too bad off but you're going to change them anyway and don't do a KAM reset, then the driveability might not be affected that bad.

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