Gas mileage decreased

When I first purchased my Toyota, I was getting on average over 23 mpg. I have 150k miles now and I must use 93 octane just to get 18. Changed plugs and wires. Very briefly got 22 mpg for the first 10 miles and then it dropped back to where it was before plugs. Thought about trans and torque converter but transmission people says that wouldn’t change anything. Stock no amendments done to the vehicle. Suggestions?

 

I suggest you set realistic expectations for your 4Runner. The 18MPG is standard for a lot of owners. But you don't need 93 Octane to get that. I average 20.5 - 21.0MPG for the tank average. I live in "Flat Land" country and 98% of my miles are highway miles.

 

Could be anything. Your foot got heavier, more ethanol in the fuel, etc. As far as mechanically, brake calipers are know to be sticky on 5th Gens. Check to see if you have a brake dragging. I've replaced the front calipers on my 2011 at around 150K. It was warping rotors something fierce. That would definitely increase fuel consumption.

 

Octane has nothing to do with fuel economy.

 

How are you calculating?

Computer average per tank?
Computer After Start?
At the pump? (Miles/Gallons)

If you’re cruising below highway speed you can hit 22 easily on the After Start gauge but add any elevation, stops, etc. it will drop like a rock.

What driving conditions were you seeing 23 MPG? That is almost not possible except in some of the most efficient driving conditions.

Has your effective range dropped at all? If your driving habits have not changed, are you filling up more often or not?

The tough part is making sure there actually is a problem and not just the computer estimating differently. (if you coast in neutral, does it coast as you would normally expect?)

(and of course there’s plenty of potential changes that could affect it, tire pressure, new tires that are E load, a lift, rooftop tent, etc.)

 

Interested in what "wires" you changed???

 

I’m just here to see how this plays out….
Smells fishy to me.

 

OP you averaged over 23 in a '15? That's some huge numbers for a 1GR, and I doubt even the new 6th gen hybrids can do that. I don't think I can even hit 23 on flat highway unless I slow down to about 60 with stock tires. I assume all 150k miles are in the States by your profile and not using some foreign gallon measurement like Imperial Gallon before?

 

1st suggestion: quit wasting money on 93.

How do you figure you got 22 MPG for 10 miles? I assume you're going off the computer, which isn't always the most accurate.

Almost nobody has ever averaged over 23 MPG on a 5th gen 4runner. Were you basing this off of the dash readout, or hand calculated?

Edit: not trying to be argumentative. Just asking.

Also: Welcome to the forum!

 

93 will burn faster. Do Not use it again.

 

???

 

Did you reverse your route?

Aka first 150k miles you drove downhill and got towed back

Now you drive uphill both ways it seems

 

Don’t forget to helium-fill your tires to reduce unsprung weight.

 

Welcome from Wisconsin!

 

That’s pretty amazing mileage you were getting. The most I’ve gotten is 18.2 per gallon. We have stop and go traffic where I live and sometimes I can get open road but not often. I use 87 . I also have a 2006 highlander it started getting bad gas mileage well first I found out my neighbors were helping themselves to my gas tank. But I did discover one of the back rear calipers was sticking. I had another issue with electronic stability control had to be reprogrammed you could feel the vehicle not rolling properly