5th Generation Poor Fuel Efficiency Causes?
 

Hello,

I have a 2013 SR5 7 passenger with 15,000 miles (23,000km) on it. I am a retired pro race driver and broke the engine in properly and have kept the service up to date. I always use name brand gas.

I drive 85% Highway and 15% city @ 70 mph and 35 mph respectively. My daily commute is FLAT along a ocean over a large river delta and I do not start fast from the light. (ECO is green 95+% time)

When new 1 year ago I was getting 19 MPG on this type of driving... now I am at 14.6 mpg!!! No 4wd, no snow, no trip into mountains. Toyota service does not want to even look at this.

I have reset the ECU back to factory specs before this last fill up.. and no change.

OOO Wise and long time members (that may work as a toyota tech,) what could go wrong mechanically in this to cause the MPG to drop like that?

Burns not a drop of oil. I am perplexed... could it be a bad O2 sensor???

Looking for more ideas before I present my problems more formally to service.

Thanks for reading and your help.

(The funny thing is that I will most likely do a lift and some other mods that will make the issue worse... but if I am already at 14 MPG where will I end up??? Lambo LM002 territory?)

1st, did you do the math to calculate mpg or are you trusting the dash readout?

2nd, have you made any modifications? New tires?

Clarification to questions
 

I did the calculations based on fuel in / odometer read. Had an accountant friend of mine confirm my data. (The data from the computer is pretty close though within .5L/100Km.)

I did buy new tires as my truck was also not too happy staying on a straight line. Went with michelin LTX MS2 stock size that were to improve milage as well as sidewall stiffness. (Also stock alignment was horrible! 0 castor one side and 2.5% on the other... went to 4% both sides with 0 toe in... so even alignment with stupid toe in can't account for this. After the engine is fixed I would like to experiment with a little more toe to make things track even straighter.)

Otherwise totally stock.

Thanks for your help.

There are certainly seasonal variations that could affect MPG, but you may have taken those into account -- summer/winter gas blend (at least in the U.S.), temperature... Tire pressure could also vary as temperature changes.

You could have some sort of frozen caliper or e-brake or something similar that is reducing efficiency.

Was there any rapid change in MPG or just gradual decline over the year?

The Michelins are anywhere from 4 - 8 lbs heavier per tire. I'm not tire savvy enough to determine if that much weight would be a determining factor, but it might. I put heavier Wrangler TDs on my old Tacoma V6 and noticed a drop of about 2-4 MPGs. I'm looking at new tires and am trying to stay with roughly the same weight as the Deulers (40lbs).
Did the change in economy happen before/after the new tires? If after, how long after? Did you have an oil change about the time you noticed the change? The wrong oil could impact the economy (It happened to me in my wife's civic. The wrong weight impacted our MPGs by roughly 5-8).
Do y'all have a fuel difference for the winter? We are starting to see winter mix here, oh, and I hate it!

Still searching
 

Thanks for the suggestions.

OK Forgive me if I have forgotten one in my response.

The efficiency went over time (6 plus months)

The tires are 40.7 pounds by the website specs for this size so I don't think that is the issue. Plus weight would affect city driving more than highway. It is my highway that has really suffered. Last fill up was 95% flat highway and WAS WORSE than the fill up before with up to 25% city. (Rare occasion running kids around the city for a swim meet.) Tires are inflated with nitrogen and have been checked for pressure since the drop in temp.

When the truck was new I was running winter gas and getting over 19.5 mpg so I do note a drop in all my vehicles for winter gas.. but also think this can't be the issue as it is a gradual loss over 6 months or more.

Brakes have been checked and no problems there.

Just really mystified at this as traveling at 70 mph constant speed should get better milage than stop and go to 35 every 1-2 minutes. (Typical Vancouver traffic.) My latest readings are 14.1 MPG with almost all highway driving.. the one before that was about .5mpg better with MORE city driving.

Any other suggestions? Can a transmission cause friction without making noise or smelling badly? I am suspicious of this component as it seems to always be lugging the engine and kickdowns take almost full throttle... But then again at speed gearing should not make a difference unless the bearings are shot??? Can any of the shafts do this without failing or leaking?

Drives great except for the transmission lag... but I chalked that up to Toyota trying to max out gas milage with low revs.

It is a real mystery... talked to an old friend that was one of the crew that worked on my formula mazda... great race car mechanic... no ideas about this 4runner however.

Any Dr. House types out there that specialize in 4Runners?

Thanks

When you said you reset the ECU- how did you do that? Disconnect the battery for a few minutes? Sometimes it's good to do that to get back to baseline.

Disconnected it for about two hours.

Although I was a little suspicious that this did not do what it was supposed to do. Why? Well, the trip computer, eco settings, etc... all were blank... BUT the homelink, radio presets, navigation setting and history, and all my phones were still connected via bluetooth.

I was kinda hoping that the whole thing was going to be a real pain to do... re-syncing phones and all that. But having this other info stay on board despite the reset makes me wonder???? Hmmmmm...????? Did the tranny and ECU actually reset?

It's probably a long shot and I don't know how it works in Canada, but are you having to use a certain percentage ethanol gas? We have some gas stations that use it more than others and that stuff is terrible for our engines. I don't think most stations use more than 10% ethanol but even that hurts our mileage....
.

The one thing that's coming to mind for me is a bad catalytic converter restricting exhaust flow. I know it's a long shot with the runner being so new but that would certainly cause a drastic drop in fuel economy. Aside from the bad mileage I don't guess you've noticed any performance decrease? A/F being off could cause that which I would like to a bad primary O2 sensor but I think you'd be able to notice a drop in throttle response and general performance. Check your intake system and exhaust for obstructions. I'm betting you issue is there or the A/F being off.

Thanks Grey Ghost and Bootleg,

Yes we are dealing with the ethanol problem as well. (I think that there is legislation that limits to 10%.. though I might be wrong.) I have been running all E10% fuel since new... but Chevron offers 0% Ethanol in the Supreme Plus 94 octane. Tried that for one VERY EXPENSIVE tank... NO difference.

The Cat and the O2 thoughts are the ones that provoke my brain to think about these possibilities the most. I wonder if I am a victim of a frog slowly being cooked in a pot? You know the idea that if you put a frog in a hot pot of water they will just jump out... BUT if you raise the temp slowly they stay in because they can't feel the change. Not having driven another SR5 since this all started, I have no "baseline" to compare it to. My other car is really quite fast so the 4runner has always felt very slow to me... but speed is not the 4runners forte.... so it never bothered me. I wonder if the performance has suffered as the milage has changed???

Great thoughts! And ones that I will share with the dealer. I think I will test drive another SR5 while they are looking into the Cat and the intake / O2 A/F mixture.

Thank you! -to all the members for their help on this. Great forum! (It's going to cost me some money though.... as I look at the pics of your rigs with nice mods I feel a hole burning in my pocket!)

This might sound weird but reading some folks post saying Eco was useless I turned mine off. I've been actually avg 2 mpg better and been enjoying better acceleration to boot, LOL.

With ECO I've been avg. 15.8 mpg (my 4R has 2.5"F/1.5"R level kit, Baja Rack, Gobi ladder, 275-55-20 Nitto Tera Grapplers tires)

For a month now my mpg is hovering around 17.6 mpg with ECO off. I do a lot of Houston traffic driving, LOL.

Try turning ECO off and see if it gets better.

Eco is just a light. It doesn't change the transmission shifting profile or throttle response in the 4Runner like it does my Prius. The temperatures have probably just dropped to the point that you aren't running the AC 100% (only 95%, hehe).

To the OP, see if you can find someone with an SR5, reset your fuel economy readout, and run the same loop back to back (no drafting!). That will tell you if it is a condition issue or a vehicle issue. Second, get an app on your phone like Gas Cubby. I use it for all of my vehicles for this reason precisely. I know when I changed my tires, so I can track my averages before and after the tires. Going to an A/T from my dualers, I'm seeing a drop from 22mpg down to 20.5mpg or so. Your tires, despite being heavier, shouldn't have impacted your mileage as much as my Goodyear Wrangler SilentArmor A/T (light truck load rating).

I'm taking a similar hit on MPGs as Quentin did since I switched to Bridgestone Revos.
OP: Take it on the hwy at 60-65, reset your meter once you've reached speed, drive at least a few miles and report that MPG. It should be over 20 at least for this kind of test.
No roof top cargo box?
What tire pressures?