Apparent significant change to fuel economy

[Snakedoctor]

I’ve got a 2022 Lariat Supercrew 3.5L, FX4 that I’ve had since brand new. I usually could baby it and my trip odo would show I’m in the mid 18s to high 16s. Back in April I put new tires on, 265/75r18 so just a half in bigger and about 14lb heavier, depending on which source. It’s Falken Wildpeak AT3W. Some sites show they are 37lbs some show 50lbs.

I’ve been driving with them since mid April and didn’t notice a hit then. Now fast forward to July-August and my MPG seems off. My current trip is at 14.5 and I reset the avg mpg and it’s sitting at 11.6. There’s no lift/level or anything. I do drive in very short trips throughout the week but even before it was never this low. It seems at an idle this truck gulps the fuel down. I watch it drop .3-.5 just at a single light since resetting the avg. I run regular 87 fuel but will try some premium next go round.

I find myself making an hour drive every now and then on a backroad route and before I could get up to 24mpg on that and last I drove it I was barely in the 19s. Same driving habit. I’ve replaced the engine air filter about 8k miles ago, right at 20k lifetime and the filter seems rather clean still.

Anything else I should check? I know it’s a truck and not for good mpg but seeing what I have got before and nothing major changing makes me wonder if there’s an issue.

If I left out any other information let me know. Hard to put driving habits into text for me.

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[astro_fusion]

I wonder if your battery is on the way out and maybe it's your charging system taking up the slack and taxing your fuel economy?

 

[My 2ND Ford]

How many miles on your truck? Could you benefit from new plugs if your milage is high? It's possible your larger tires are making your milage off, but it would seem to have been apparent before now. If you are not noticing anything else wrong with the truck, eg, rough idle, hesitation on accel, poor accel, then I would chalk it up to the heavier and taller tires. You could try a can of injector cleaner with some top tier premium gas and see if that makes a difference . Make sure you read the instructions on the cleaner if you do try it as you usually put it in with an empty tank and only put in X amount of gas. Good luck.

 

[Snakedoctor]

How many miles on your truck? Could you benefit from new plugs if your milage is high? It's possible your larger tires are making your milage off, but it would seem to have been apparent before now. If you are not noticing anything else wrong with the truck, eg, rough idle, hesitation on accel, poor accel, then I would chalk it up to the heavier and taller tires. You could try a can of injector cleaner with some top tier premium gas and see if that makes a difference . Make sure you read the instructions on the cleaner if you do try it as you usually put it in with an empty tank and only put in X amount of gas. Good luck.

I have 28,500 miles.

 

[Snakedoctor]

I wonder if your battery is on the way out and maybe it's your charging system taking up the slack and taxing your fuel economy?

Is that really a possibility? Because if so then that’s probably it. My battery is the factory battery and I do believe it’s going out since there’s times the passive entry won’t recognize I’m trying to unlock and the “do-do-dos” come from the cluster which I’ve read is a symptom of a diminishing battery.

 

[2.7tugger]

Engine air filter and tire pressure should both be checked

 

[JBrochacho]

Did you recalibrate (in Forscan) for the bigger tire size? Love Falken Wildpeaks but those muhfu*kas are heavy.

 

[Chappy133]

Could this be a seasonal fuel blend issue? Summer blend vs. Winter blend.

 

[TxAgs2012]

It's the tires.

I got 285/65R20 Falken AT/4's, and my mileage dropped from 21 mpg on the hwy, to 15-16 mpg.

2023 F150 Platinum with 3.5L FX4 Max Tow

 

[Snakedoctor]

Engine air filter and tire pressure should both be checked

Filter looks clean, only ~8k miles with it. Tire pressure seems right for tread contact with road

Did you recalibrate (in Forscan) for the bigger tire size? Love Falken Wildpeaks but those muhfu*kas are heavy.

I did not because it’s such a minor change. 32.1 vs 32.6. It’s not an LT tire so these really aren’t that heavy

Could this be a seasonal fuel blend issue? Summer blend vs. Winter blend.

If memory serves correctly usually summer blend has is better over winter

It's the tires.

I got 285/65R20 Falken AT/4's, and my mileage dropped from 21 mpg on the hwy, to 15-16 mpg.

2023 F150 Platinum with 3.5L FX4 Max Tow

That makes sense for that size, 67.5lbs a tire. Mine are an SL tire not LT. I wouldn’t imagine such a significant drop with minimal weight change.

 

[TxAgs2012]

You be surprised. Next time you’re driving, watch the turbo boost gauge and see how often the truck is using those turbos. The OEM tires are really good about keeping the truck out of the boost. I noticed it when I saw my rpms are usually the same as before, but then looked at the boost gauze and saw my turbos are kicking in far more than before I swapped the tires.

 

[FaaWrenchBndr]

Keep in mind you not only have to consider the weight of the tire affecting mileage. You need to consider the tread design affecting mileage. A more aggressive tread creates more friction if you will thus lowering fuel mileage. There is a reason why manufactures put the tires on that they do.

 

[Snakedoctor]

You be surprised. Next time you’re driving, watch the turbo boost gauge and see how often the truck is using those turbos. The OEM tires are really good about keeping the truck out of the boost. I noticed it when I saw my rpms are usually the same as before, but then looked at the boost gauze and saw my turbos are kicking in far more than before I swapped the tires.

Im so rarely in boost though lol. I was driving a few weeks ago and I thought to myself is this gauge even working so I pressed a little bit to get it going lol.

Im thinking it’s got to just be from some extended idling for this tank. After this tank and I try some premium with a long drive I’ll see where it gets. Between idling and my constant short drives ~5 miles a day I think have the most to do with it.

 

[SilverSpur]

I’ve got a 2022 Lariat Supercrew 3.5L, FX4 that I’ve had since brand new. I usually could baby it and my trip odo would show I’m in the mid 18s to high 16s. Back in April I put new tires on, 265/75r18 so just a half in bigger and about 14lb heavier, depending on which source. It’s Falken Wildpeak AT3W. Some sites show they are 37lbs some show 50lbs.

I’ve been driving with them since mid April and didn’t notice a hit then. Now fast forward to July-August and my MPG seems off. My current trip is at 14.5 and I reset the avg mpg and it’s sitting at 11.6. There’s no lift/level or anything. I do drive in very short trips throughout the week but even before it was never this low. It seems at an idle this truck gulps the fuel down. I watch it drop .3-.5 just at a single light since resetting the avg. I run regular 87 fuel but will try some premium next go round.

I find myself making an hour drive every now and then on a backroad route and before I could get up to 24mpg on that and last I drove it I was barely in the 19s. Same driving habit. I’ve replaced the engine air filter about 8k miles ago, right at 20k lifetime and the filter seems rather clean still.

Anything else I should check? I know it’s a truck and not for good mpg but seeing what I have got before and nothing major changing makes me wonder if there’s an issue.

If I left out any other information let me know. Hard to put driving habits into text for me.

I use a kind of troubleshooting flow idea. I used it when isolating circuit board of equipment issues. It's last good first bad or when was it good and then when did change happen. It your change happened when you put the tires in. Tire first bad. If the tires are low warranty miles then they may be made of a soft rubber causing rolling resistance. I go for 65,000 to 70,000 Mike tires. Less rolling resistance with proper air presure.

 

[Calson]

The more aggressive and th e deaper the tread the more energy is lost from tire scrubbing. The fleet operators have gone to tires with much thinnner tread to improve fuel economy and the savings in fuel more than compensate for needing the tires to be retread after fewer miles.

Check out the tires for high mpg cars like the Toyota Prius or the Ford Fit for an idea of the type of tires that provide the greatest fuel economy.

Aggressive treads tend to provide worse offroad performance as they dig down instead of allowing the vehicle to float over the surface, especially with sand and snow. The mud tires on my first Willys 4WD made it very easy to dig down and then bottom out the rear differential and I had to modify my approach.

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