Another my mileage dropped recently post.

2019 SR5 and I was previously seeing ~14mpg town (3 mi. short trip to work) and ~17.5 on longer hwy trips. I am now seeing around 11.3 mpg in town and 14.5 hwy on the lying computer screen. About a 3 mpg average drop.

I have 275/70/18's with a front level. I changed the plugs about 4 months ago and I am due for an oil change. Oh and I put on a Bakflip hard roll-up tonneau cover (heavier?) and I ran a can of Seafoam through the gas tank and a new air filter at the last oil change and tire pressure is just on the high side @ 35psi. Brakes and rotors are new in the past 5 months too.

Summer here in AZ has been brutally hot here with <105 days for the past month. It has also been really humid. I also use ethanol-free "blue gas" from the local convenience store.

Is this normal, I put in a new battery last week too so perhaps the computer either has or hasn't caught up to learning. I also think the hot weather is a factor as my truck seems to like the cooler air in the winter. I replaced the plugs myself and gapped them correctly and it was also doing fine after that. I am also thinking some fresh oil might help but I dont think it would make that much of a difference.

 

So are you going off of the dash calculation or hand calculation?

 

Why are you relying on the truck computer for the mileage calculation? They are notoriously inaccurate.

How many miles on the truck? Why did you replace the plugs?

More weight will always lead to less fuel efficiency.

"Fresh" oil is not going to change anything.

 

Dash PC calculations

The truck has 74K miles on it.

I preemptively replaced the plugs before a 4K long trip.

 

Don't do that.

Do a proper calculation. A new battery will mess with the dash for a couple fillups.

 

My guess would be a computer learning issue from the new battery. Maybe calculate it by hand and see if the numbers match.

The AZ blast furnace certainly doesn't help, but I wouldn't think it'd be a 3 mpg difference

 

Or if math isn’t your friend you can try something like fuelly.com

 

Did you use Toyota spark plugs for exactly this engine? Gaping seems suspicious, OE plugs don't need that.

 

This is what I use. Keeps it very simple but just typing in numbers on each fillup. Then I have a log to see how it trends.

Almost every single tank my dash calculation is within .5 mpg of fuelly.

 

One thing you might want to check is your alinement, a few potholes and maybe curbs will affect MPG.

 

Except, he will be comparing the old truck computer numbers with the new hand calculated numbers. They will be of limited use to make an accurate comparison.

 

Aren't the OEM plugs good for 120,000 miles?

And what plugs did you use and as another poster asked, why did you gap them?

 

Hey, I can do math and I am no dummy because I went to high school for 5 years!

The plugs didnt need gapped, I checked the gap would be more accurate.

I used NGK Iridium plugs

 

You got an extra year to do shop and ag? Lucky bastard.

 

I'm averaging a solid 17 MPG mixed city/hwy in my truck, hand calculated. My dash computer is inaccurate. However, it can be plus .3 or minus .3. It doesn't always read high. It sometimes reads low in my observations.

Mike

 

Assuming you went to LT tires when you bumped up in size, 35psi would be on the lower side of inflation, not the higher side. My only other comment is don’t use a regular spark plug gap tool when handling iridium plugs, they can damage the tip. (twss)

 

Small update. I stopped this morning to fill up with gas to be able to do a hand calculation of mpgs. After I pulled into work I checked the dash computer and it read 12.5 mpg. I know it lies but that is more along the lines of what it was. This is also my first fill-up since changing the battery so maybe the truck reset or recalculated itself?

 

What was your hand calculation?

 

Haven't done it yet, this was the initial fill-up to be able to do that. I have to drive about 100 miles today so I will fill up again when I get back and see how it compares.

 

If that 100 miles is all city or all highway, I would wait until you run through at least half the tank before you actually fill up and calculate. If not, your calculation will be biased.

 

Use Fuelly.com and track it...I have been since owned and it is consistent (truck efficiency-wise)...just a suggestion but I'm manic on tracking now since using it...

 

How do you link it to your signature?

 

Within the web page there's a couple options on formats to use for linking...at the very bottom of the data it has a button "Share your MPG"

 

I just joined Fuelly and my vehicle name is "I Suck Gas"

 

I must be blind. I've never logged into the actual website before but I'm in and have everything updated. Just cant figure out the linking part.

EDIT: Disregard

 

So you upsized your tires and get about 12 mpg? Not sure why so many people use Fuely who get bigger tires? Are you trying to get the worst mpg possible? 12 mpg is too good, so maybe get even bigger tires?

 

Lots of reasons to track...in northern states, winter fuels change, temperatures change mpg, fuel stations all have different blends (where I'm at) and it's a good indicator on style of driving...most importantly us fuel type, grade and time of year...easier to budget for trips

 

I got slightly bigger tires (275/60/20) and I've been tracking since 2014. Four vehicles ago. I track because I like to see how my driving is. I know that I lost maybe .5 mpg on average with the new tires so I take that into account. By tracking, I know when my driving habits are more aggressive or when winter blend fuel arrives and with winter/4wd, I lose another 2 mpg.

I don't use it as the holy grail or anything but it's just nice to see how things are going.

 

That makes prefect sense. Sorry I assumed the tires you got were larger than that. But only a little over one inch taller. That may still be more than 1 mpg for one inch. I also keep track of mpg. Probably too obsessed with it as I only drive 12k miles a year so justtified the lower mpg compared to my previous F150 5.0 that got 19mpg using Fueley.

I'm getting 16.8 with mixed driving with 2wd and Ridge Grapplers that are stock 275/55/20. They get about 1 mpg worse than P road tires. The 4wd will also be 1 mpg.

The thing is we only get snow maybe once every 10-20 years that even sticks to the road so would have a far greater chance of mechanical failure with 4wd than actually needing it.

Also see lot of people on Fuely who get terrible mpg because of larger tires. Sorry I thought you were one of them but that's very reasonable. I'll likely go with Michelin Defenders for next tires as they are 10 pounds lighter and 1 mpg better. Although see how the Grapplers do. I worry about them on wet pavement. I've tested them some and will lose traction.

I don't care about what tires someone whants to use, or what mpg they get, but do actually dislike loud trucks or vehicles because it's inconsiderate to everyone else. Sorry that's a little off topic but usually bigger tires, low mpg, and loud trucks go hand in hand. Sorry if that offends someone, maybe that's all they want anyway. Life moves on. I'm not on a busy road either.

 

No worries! It's actually the OP that has the other tires and a front lift with really bad MPG on the dash. I was just defending the use of Fuelly lol

But I agree with you, getting larger/heavier tires with a lift and then complaining about mpg's (not saying anyone on this thread is doing that) is always crazy to me.