“Perfect” highway mileage barely 15.6mpg

Decided to stop hijacking the other thread about this.

Disclaimer: I bought this truck for hard use as a pickup. I am not a hyper miler but I do care that I either got okie doked by Toyota or there is something wrong with my ride.

Background: I live in the Southeast (where it’s flat) in a very rural area. The gas station is 18 miles away. All my driving that isn’t 4x4 off-road is ideal for fuel economy. 55mph 2 lane roads with no traffic.

For the first several months I had this truck I never bothered to track mpg because I was always in the woods using 4LO. I then upgraded to 275/70/18 E rated KO2s. The garbage OEMs kept popping. I have no other mods.

Issue: I barely get 15.5mpg trying my best, and with normal driving I get closer to 14.5. This is with no 4WD or off-road driving of course. If I drive into the woods even for a short afternoon trip to fill up a Cat with diesel I will see mpg in the 12s.

I have used the same gas pump to refuel multiple times and compared fuel to miles driven and it agrees (0.2~mpg difference) to the tank average on the display.

Why is my fuel economy so poor? Highway on this is rated to 23. I’ve never even seen close to 20. I mainly want to make sure nothing is wrong.

Here’s an interesting observation I made this morning. Not sure if it’s related or I’m reading the gauge wrong but shouldn’t eco all green be the most efficient? I think it’s backwards. Look at the RPMs. One is floored going uphill the other is coasting downhill.

 

Honestly man I would contact your dealership and have them at least look into it at this point, what’s the worst that could happen?

 

I drive very similar roads(closest stop light is 10 miles away, all 50 or 55 mph 2 lane roads) in my f150 Ecoboost and average 15.5 or so in the winter months with 315/70R17 KO2’s, but they are C range and barely weigh more than your 275/70’s. Probably combine with your heavier oem 18’s your wheel/tire combo might be heavier than mine.

15’s in the winter might not be too crazy

My Lexus GX eco gauge is the same way. Seems counter intuitive. You’d think the more you fill the gauge the more Eco you are being

 

Also your miles driven are likely incorrect with the 275/70’s unless you are tracking with a GPS. That would make your mpg’s seem lower.

Oh and make sure you are running enough pressure in those E range tires. I wouldnt run any less than 45 psi. Unlike SL tires, e range tire load rating is directly proportional to their inflation pressure. To properly support a 1/2 ton truck and its axle ratings, the pressure needs to be somewhere in the 40’s. Ram puts similar sized E range duratracs on the Rebel model and the factory pressure is 55 front, 45 rear. Ford also has e range tires on certain F150’s and specs 45 psi.

Running too low of a pressure in an e range will cause considerable energy loss due to added flex of the heavy sidewalls. You’re just burning energy compressing them as they rotate

 

lol 50 in a 35

 

A mpg comparison before tire change would have helped to quantify that impact. E loads are very heavy so their impact would not be zero.

I live in GA but work in AL. Going to site is elevation drop and I have seen 21.9 mpg in warm weather going mid to high 70s on interstate with just me aboard in 2wd truck Return drive home uphill is 2 mpg less. If I drove the return route with a 4wd, non stock tires, cold temps and a lot of cargo or people load I could well imagine that dropping into the 17s.

Lots of variables.

 

Not judging just noting something funny.

 

This is interesting, I would maybe have it looked into. I am driving 275 70 R18s KO2s on the three inch lift in the inland northwest. Not flat, varying speeds, stop and go, hills, a lot of 4 hi because of snow, and I average 17. This is also in some very cold temps. I usually see upward of 19 and sometimes 20 if I am just cruising flat and going between 45-65.

I calculate by hand at fill ups as well to not just trust the computer. I have been impressed with my mileage considering I’m lifted with a larger tire. I am beating my Tacoma, which is good enough for me. I hope you can get something figured out. I would be a little bummed about that as well.

 

The good part about these turbo'd engines is they can be tweaked with software. I have not had my truck very long to investigate that, but I am sure that tuners will find a way to bring a tool to market that can be plugged in and give users a way to adjust for economy, towing or power.

I know that the bigger tires are a killer to the mileage. The ratings provided by Toyota would seem to be misleading as these are based on the nearly bald starter tires that weigh half of what we can find in the tire market.

We know that the truck has a drive mode selector which changes the engine program for higher revs, towing, etc... If this could be further developed, I am sure that there will be some options for improved mileage.

I had a TDI which started out with 90hp and 150 ft-lbs in 1999 and without too much work, mostly tuning, I got 165/315 (dyno'd) out of that little 1.9L engine. The powerband was very smooth and mileage was over 50 mpg (putting my foot into it all the time). When I towed my travel trailer with it, we got more like 30 mpg. This was still achieved while not babying the throttle!

What I am trying to say is that there will be tuner options in some form if they don't already exist.

 

Small displacement forced induction vehicles seem to take a bigger hit for any increased load. It's not just Toyotas. You went larger and heavier on the rotational mass. You're gonna pay at the pump. One thing to keep in mind, that if you didn't get the speedo calibrated for the larger tire, then you are getting better mileage that it shows. You have to account for the added distance the larger tire travels per rotation.

 

You also have to realize that the EPA number is an estimate that isn't actually tested out, and it's not realistic to expect to achieve it. Many do not.

You're not being dinged from the EPA number down to 15. You are being dinged from whatever your actual mileage was before the tires down to 15.

 

Shocking, right? LOL

Just for reference. It's older info, but still shows the general premise.

 

One of those images shows you turning 4,000rpm. Most people’s definition of “driving perfect” is anything but. Eco driving won’t ever see 4,000 rpm.

 

You’re not losing 8mpg from just changing tires. Something else is going on.

 

Read the line above it. That was kind of his point.

 

The lower you are in the eco gauge the better your fuel economy. As it starts to climb it gets worse. And i agree w the above statement. IOT get the best mileage you need to usually keep rpm below 2000. Occasional spikes for passing and getting to speed happen, but if you generally try to stay at 2000 and below you will see your best MPG.

 

^^
You would think that more green means better fuel economy. My Ridgeline had LED dash rings around the instruments that would change colour from green to white. White would appear when going uphills or driving it with more foot. Green would appear on the downhills and when just rolling along. But that's Honda so who knows?

 

hahaha. Sarcasm is lost in text lol, and yes the eco bar is 100 percent counterintuitive.

 

They take a bigger hit because they are more efficient to begin with. With enough load, all engines making the same power will settle around the same MPG(IE towing).

People think these small displacement engines are supposed be more efficient everywhere but eventually you run into the limits of how much energy the fuel has. Where they are more efficient is where a big loafing V8 is the least efficient(light load)

 

What foot do you brake with?

 

You talk of woods roads, fueling a CAT with diesel. You’re hauling diesel fuel cell and tools I’m assuming. What’s the average extra weight?

 

70-75 in 65mph

https://imgur.com/a/ikgCsVJ

Show us all 3 data points, the end of trip, your avg on your speedo and infotainment screen

 

I'm in a similar situation, but don't think anything is wrong to address your main concern. I think its the load E rating.

I also switched to 275/70/18 E, and lost about 5mpg on my stock truck!
Stock tires was 24/19mpg, load E tires are 19/14mpg at best.

Kind of worth it to me because I drive forest roads also, and want the peace of mind of not popping a tire. But I might research more for my next set and drop a rating.

 

Out of all the fuel economy threads, this one is the most confusing. We don't even know what fuel economy you were seeing before you changed to larger tires. Also, we don't know how fuel efficient your brand of tires are compared to other similar size tires.

 

My bone stock 2016 gets 13 all day every day.

Welcome

 

Great news! That should make a pretty noticeable difference. Figured it had to be something like that…

 

So this is why the Tacoma still has drum brakes

 

Did you see if the pads are wearing evenly and if the slides are well lubricated ?

 

Wow, you might want to look at the rotor as well in case it got overheated with the pad contact. Nothing worse than brakes pulsating!