Extra fuel usage all of a sudden

Hello Team,

Having a fuel usage problem. Here is the story, rear brake driver side locked up, turned out the pads we stuck against the rotor. Replaced, fine (with the help of this forum).

Figured i should check all the brakes as i was still getting a grinding noise at the front this time, found front passenger side to have a stuck caliper. Replaced, fine.

Truck suddenly went to giving 14.0L/per 100km (16.80 mpg).

I have owned the truck since new and it always gave 14.1L/per 100km (16.68 mpg).

Now it is worse and i am getting 14.6L/per 100km (16.11 mpg).

I can't work out why it is using the extra fuel per 100km.

Here is what i have done so far:

1) Jacked up truck, spun each wheel to make sure no brake grinding
2) Checked and topped up tire pressure to 32 psi
3) Changed the oil
4) Changed the air filter
5) Greased both drive shafts and spider joints
6) Checked no excess weight in the car from normal

Throttle body was done a few months ago.

No error codes and truck drives fine, although it does seem to take a few seconds longer to pick up speed.

Any ideas why the extra fuel usage?

2016 4Runner Limited, 112000km (69000 miles).

All maintenance is done by me so i know its got correct oil type, filters, air filters, etc.

Thanks,

 

Going from 16.68 to 16.80 to 16.11 isn't a huge difference. Hell, if it's a very windy day my truck can drop 2MPG overall. A strong headwind, bad roads, bad gas, etc... All can contribute dramatically to my change in MPG's.


You're losing less than 1MPG overall. I wouldn't worry about it.

 

Don't get me wrong, not saying this because of cost, more of a "what's wrong and is it going to get worse?" type approach.

 

I don't think anything is wrong. It sounds like you're maintaining your vehicle very well. Will it get worse? I seriously doubt it. It WILL fluctuate though. Your tank MPG's may jump up and then back down.

 

I track every tank, have for years. Basically every tank I have a variation about that size. I wouldn't worry about it unless you have a larger drop, over a few tanks.

That little variation could have just been from you driving aggressively to bed in the brakes, but perhaps you had some extra idle time while working on it.

My last three tanks were 19.91, 19.63, 18.97. I know the most recent tank was lower because twice I got stuck in stop and go traffic.

 

How are you calculating fuel consumption, gas pump readout between fill-ups divided by odometer reading? Don't rely too much on the vehicle's own sensors as there's no flowmeter in the fuel system.

When was the last time you replaced the differential fluids?

 

Using only the cars dashboard reading.

Front / rear difs and trans drain / refill done at 90000 kilometers (roughly 60k miles).

 

On any vehicle, but especially these, don't focus so closely on mpg. As others have said, it'll fluctuate almost with the 4Runner's mood. Here in Ohio, the advent of 'winter gas' in November signals itself by knocking off 2+mpg, for maybe 4 months. There are too many variables to make it worthwhile tracking 1-2mpg changes.

 

0.5l/100km is not a huge difference so probably it's something small changed like brakes might still need a bit of tuning. Maybe pads touching rotor just a bit in one place. Or it might be not related to that - I've read that some gas stations started count liters a second or two before actual pumping gas. So maybe next time you fuel up - pay attention to the display on gas pump. Or try other gas brand, maybe they decided to put a little more ethanol in gas at your favorite gas station. Another idea - it could be that your tires got worn out a little so your 32 psi today might provide a little more resistance than 32 psi a year ago.

 

Lol you're lucky to get within +/-1 mpg of actual with the dash reading. 0.5 mpg "change" is noise.

Was the transfer case filled with LF fluid or regular 75W90?

 

For the transfer cases i used Amsoil Severe Gear Oil 75w-90.

Now that i think about it, my last two fill ups were not at my regular gas station. Might wait until it burns off this fuel and fill up again at my regular place.

 

Or just accept that your 4R isn't going to return identical fuel mileage numbers tank after tank unless all factors remain identical. Which they won't. Ambient temperature and humidity alone can affect mpg more than you're seeing. Nevermind driving habits and conditions and 100 other factors.

 

It just seems odd though, the truck as always given me 14.1L/per km, the only time it differed since new was when the rear brake pads locked up.

Do you think the driving it around with locked pads did any damage? It wasn't until i saw the brake dust and grinding noise did i work out something was wrong. Looking at the pads they must have been stuck for a while as it was completely worn out. The noise started when the pad was down to metal.

 

Didn't change oil every 1K.

So you get .7less mpg this tank.......

 

If you're relying on the truck's calculations, and you haven't reset the meter in the truck since the locked-pads episode, then that event is included in your current average. In that case, reset the meter, and give it a few tankfuls to settle out.

I personally would be happier with this exchange of info if we were able to convince you to pay less attention to your MPGs. Unless you drive identical trips on identically flat roadways, with identical fuel quality and quantities, at identical speeds and acceleration rates, with identical traffic, identical stops, and zero wind, you're not going to get identical fuel mileage measurements. The fact that you have gotten that consistent rate of fuel consumption makes you an exception, if you read on this forum. If nothing else, that tells us that you are a very consistent driver, which is good.

 

Thanks, will pay less attention to the dash.

 

When something goes wrong, it is more of a difference than what you are seeing. The likely explanation is that you got bad gas or some headwinds while driving.

 

I know for me, my mileage went down when my boy Cosmo was wearing his hat. So now he has to leave it at home, because I am saving up for a bottle of Fortaleza i had to put my foot down.

 

Yeah, that makes sense. But OP never mentioned a dog OR a hat.

 

I had a huge breakfast this morning, and it impacted my MPG on my drive to work. I only got 20.12 MPG. I usually get 20.89!

This always happens when I eat chorizo n eggs.

 

Doesn't the gas compensate, since it's lighter than air?

...or maybe there's a delay...

 

This is where you turn on the seat heaters. According to thermodynamics, the higher the combusion temperature, the greater the carnot efficiency: https://www.e-education.psu.edu/egee102/node/1942

 

Dibs on doggie daycare for Cosmo if on the East Coast.

 

Glad to see someone else has my sense of humor - you beat me to the punch!

 

Gas quality, wind and I can confirm the effects of air temperature on MPG's as stated two posts up. This is the second winter for my (new to me) 2021 and for both winters, when the air temp drops below 50ºF so does my truck's mpg. Just yesterday the morning air temp hit 45ºF and the reported mpg was down to the low 17s.