Low MPG - Out of ideas

[heiser]

I've been having MPG issues for quite some time now (6+ months). I thought it was frozen calipers, but I've ruled that out now. I've been averaging 13-15mpg pretty regularly with 15mpg being mostly highway miles.

I'm not an spirited driver. I drive pretty modestly.

2004 4wd Sport V6, 180k miles

Here are some (possibly) MPG related mods I've done:

roof rack (w/ wind fairing)
265 70 17 bfg ko2
UCAs / shocks / springs
~3.5 inch lift (slightly nose high)

Here's what I've tried to fix it:

Seafoam additive to gas tank
Cleaned MAF sensor
all spark plugs
air filter

5th gen front calipers
5th gen front rotors
front brake pads (~1 year ago)
5th gen rear calipers
4th gen rear rotors


I have a hard time believing my lift or roof rack are creating THAT much wind resistance. I know my ko2s are one size above stock, so I'll drop some MPG there. My rear brake pads aren't worn down, but they seemed a little difficult to slide in the new calipers. I bought this 4runner used over a year ago, so I don't have a frame of reference for how well they slide when new.

Any help would be much appreciated. I know "smiles per gallon vs miles per gallon", but I road trip a lot and am out in the forest pretty often where low MPGs is tough.

 

[Morphyne]

I would say it's your aerodynamics. How do you expect to get good gas mileage when you're lifted 3.5 inches and a slightly nose high? I bet f you let the front down some you'd pick up 2 mpgs.

 

[truman3]

I would say it's your aerodynamics. How do you expect to get go gas mileage when you're lifted 3.5 inches and a slightly nose high? I bet f you let the front down some you'd pick up 2 mpgs.

^^^
This is real. I put a roof rack on and dreaded a loss in mpg but didn't see anything after 3 tanks. Few months later did a "mild" 2.5/1.5 spacer lift that raised and leveled it and saw a 1-3 mpg loss immediately.

19.5 to 17.8

I do a lot of highway driving and I believe the combo of lift and rack resulted in the loss due to aerodynamics. I started noticing crosswinds more for sure and the overall drive changed enough for me to notice and I was okay with the mpg at this time.

In addition to aerodynamics there is a difference in tire size and weight to consider...

FF a few months and I added some Fuel 17x9 wheels and Nitto Trail Grappler 265/70/17 and lost another 2-4 mpg loss immediately. It's a 10 ply aggressive mud tread tire that weighs almost twice that of my stock tires.

14.2 to 15.5

Last week I changed to TRD 17x7 and Hankook ATm 255/75/17 and gained most of that loss back. Two tanks in a saw a 3-4 mpg gain immediately. Taller tire, but skinny and half the weight of that Nitto.

17.4 to 18.2 - only two tanks in and I'm happy with that.


For reference mine is a 2008 Limited V6 RWD

Sent from my iPhone using Tapatalk

 

[KDKKJS]

The 4runner is slightly under powered, some would say very under powered.
The engine power output verses the weight just dont leave a lot in reserve. That being said, a gentle foot will get the advertised mileage or close. So when you add anything that effects gas mileage, the MPG drops quick. So you add a lift, more wind resistance, big aggressive tires, more rolling resistance, racks, whatever, your foot has to push more and further. How can it not effect MPG? I see this all the time, when people start adding lifts and tires and wondering why the MPG and the nice smooth ride you used to have goes away, steering wheel shakes start, etc. Just switching to a more aggressive tire alone, even the same size, will drop MPG, it has to happen. Nice subtle street tires have way less rolling resistance then any off road tire. I'm not knocking you or anyone that adds mods, mod's are cool, we all want to do mods. You just need to realize its physics, you cant make it back up, you cant get the MPG back. I just put on BFG's KO 2's myself, and I expect MPG to drop. Enjoy your mods, but expect to pay for it at the pump

 

[ukbloke]

Are your KO2 tires C or E load range? I have just upgraded to that tire in C load range and did not notice any change in mpg. I didn't go to the E because of mpg concerns.

I do have Yakima bars with air deflector, a Thule cargo box and a kayak rack which you'd think would be worse than a full roof rack (other than weight). I have a 2.5"/1.5" lift. Typical highway miles with this set up was about 18mpg this weekend at 50-70mph including 4000 feet of elevation gain. I do have the V8 though - maybe that's actually helping me compared to the V6? Performance in the city is 2-3mpg lower.

Also, try doing the math to figure out how much 2mpg costs you over a year's worth of driving. It's not really all that bad ... ~10% of your fuel bill.

 

[jreask]

I've been having MPG issues for quite some time now (6+ months). I thought it was frozen calipers, but I've ruled that out now. I've been averaging 13-15mpg pretty regularly with 15mpg being mostly highway miles.

I'm not an spirited driver. I drive pretty modestly.

2004 4wd Sport V6, 180k miles

Here are some (possibly) MPG related mods I've done:

roof rack (w/ wind fairing)
265 70 17 bfg ko2
UCAs / shocks / springs
~3.5 inch lift (slightly nose high)

Here's what I've tried to fix it:

Seafoam additive to gas tank
Cleaned MAF sensor
all spark plugs
air filter

5th gen front calipers
5th gen front rotors
front brake pads (~1 year ago)
5th gen rear calipers
4th gen rear rotors


I have a hard time believing my lift or roof rack are creating THAT much wind resistance. I know my ko2s are one size above stock, so I'll drop some MPG there. My rear brake pads aren't worn down, but they seemed a little difficult to slide in the new calipers. I bought this 4runner used over a year ago, so I don't have a frame of reference for how well they slide when new.

Any help would be much appreciated. I know "smiles per gallon vs miles per gallon", but I road trip a lot and am out in the forest pretty often where low MPGs is tough.

Have you run a compression test ? It could be that your engine is becoming "worn out". I don't know the history of your truck but it could be just getting old. I have owned over 20 4Runners and the ones I've had with poor gas mileage are usually the ones where the engine is getting older. Not saying that this is your problem but it is another thing to rule out.

 

[Inv4drZm]

I get 14-15mpg going ~75mph or a bit over. 285s and full lift+ 1.5" body lift, V8 though.

If its somewhat easy to do, take off the roof rack for a while and run a test.

 

[heiser]

Have you run a compression test ? It could be that your engine is becoming "worn out". I don't know the history of your truck but it could be just getting old. I have owned over 20 4Runners and the ones I've had with poor gas mileage are usually the ones where the engine is getting older. Not saying that this is your problem but it is another thing to rule out.

This is the type of atypical cause I was looking for. I might take it in and have someone do this for me. It's been pretty well taken care of, but 180k is 180k.


I guess the wind resistance might be more problematic than i thought. I'm surprised it's causing that much of a drop. I had plans to have it lowered and get rid of the nose-high look already (it wasn't on purpose, and I'm not into it), so this motivates me a bit more.

Are your KO2 tires C or E load range? I have just upgraded to that tire in C load range and did not notice any change in mpg. I didn't go to the E because of mpg concerns.

E load. I got them for some extra peace of mind and sidewalls on rocky roads. I figured if C load gave me similar mpg, then E would probably drop me ~2 mpg, which I'm okay with.

When I'm losing ~2 mpg to the tires on top of the other mpg loss though, that's where it's tough.

I've read many places that lift doesn't affect anyone's mpg usually. It's the tires that go with the lift that drop the mpg. This is why I didn't think my lift would be the cause, but not everyone is nose-high like mine.

 

[heiser]

I get 14-15mpg going ~75mph or a bit over. 285s and full lift+ 1.5" body lift, V8 though.

If its somewhat easy to do, take off the roof rack for a while and run a test.

See, I bought the v6 for the bump in mpg. If v8s get better/same as me, then what's the point of having a v6 you know?

 

[ZebRuaj]

The difference between a stock V6 and V8 isn't that big.

Throw in the wind and rolling resistance you have, you were better off in the V8. Less work for it. The V6 is struggling more with all your mods.

 

[heiser]

The difference between a stock V6 and V8 isn't that big.

Throw in the wind and rolling resistance you have, you were better off in the V8. Less work for it. The V6 is struggling more with all your mods.

You're right. I didn't really consider all the mods when I bought it, but lesson learned. I'll get it the next time they make a v8 :thumb:

 

[duffdog]

I've been having MPG issues for quite some time now (6+ months). I thought it was frozen calipers, but I've ruled that out now. I've been averaging 13-15mpg pretty regularly with 15mpg being mostly highway miles.

I'm not an spirited driver. I drive pretty modestly.

2004 4wd Sport V6, 180k miles

Here are some (possibly) MPG related mods I've done:

roof rack (w/ wind fairing)
265 70 17 bfg ko2
UCAs / shocks / springs
~3.5 inch lift (slightly nose high)

Here's what I've tried to fix it:

Seafoam additive to gas tank
Cleaned MAF sensor
all spark plugs
air filter

5th gen front calipers
5th gen front rotors
front brake pads (~1 year ago)
5th gen rear calipers
4th gen rear rotors


I have a hard time believing my lift or roof rack are creating THAT much wind resistance. I know my ko2s are one size above stock, so I'll drop some MPG there. My rear brake pads aren't worn down, but they seemed a little difficult to slide in the new calipers. I bought this 4runner used over a year ago, so I don't have a frame of reference for how well they slide when new.

Any help would be much appreciated. I know "smiles per gallon vs miles per gallon", but I road trip a lot and am out in the forest pretty often where low MPGs is tough.

Well, believe it! Doing ANYTHING that increases the height profile will lower your mileage. The fact that you have a roof rack at all is probably 50% of your problem. As an experiment, a friend of mine removed his factory roof rack and got +1 mpg over stock. Also, it is known that making a truck higher makes more air go underneath it, which obviously takes away mileage. Ground clearance = bad mileage, period. Either you get stuck on every rock or you have no mileage, there is no way around it. For an example, take a look at the new "off road" z71 from chevy. That truck is 8" off the ground when looking at the front air dam, that is the only reason that the mpg increased on those trucks vs. the previous year. Now who in their right mind would attempt any type of trail with a truck that low?

 

[EdmundGTP]

For the configuration of your truck, I'd hardly call that "low" mileage.

Looks pretty typical to me.

We aren't driving Prius's..

 

[LOSTR4]

Tires dropped me 2mpg, roof rack dropped me 1-2mpg, and armor and lift netted a loss of an additional 2mpg...I'm rocking a clean and consistent 15+ mpg in town...slightly less when crusing on highway...I'm fine with the efficiency as it no longer looks like a mini-van...looks motley and fuel mileage is just an incidental to what's done...I was getting 20+ when it was stock so depending on the grade and the speed, it's muuuch less than what I was averaging prior to enhancements...first world problems

 

[fullforce]

I was getting 17-18mpg after 2/1 lift I noticed NO change in mileage

I put on 265/70-17 Genneral AT's and lost about 2-3 mpg ::crybaby:

Ive never lost that much mileage from that small of a tire change before..
I was thinking I might loose 1/2 mpg
At this point im just gonna save for gears and a body lift and run 285's next time around, might as well make it worth it if its gonna get this crappy and still look almost stock anyways!

 

[RonJR]

I wonder if it doesn't have more to do with sidewall stiffness than with the size or tread style of the tire. This thread http://www.toyota-4runner.org/engines-suspension-wheels-tires-audio-accessories/110299-lt-tires-need-more-air-pressure.html set me to thinking about sidewalls and tire pressure.


A lot of you who are experiencing mileage issues are also running Load Range E tires. E range tires have much stiffer sidewalls than a C range or a P-rated tire. Now, the interesting thing is that the actual amount of sidewall flex of a tire is pretty much determined by tire pressure, not sidewall stiffness. No conventional tire has a stiff enough sidewall to stand up on its own under vehicle weight. It's the air pressure inside that keeps the sidewall standing up straight.

However, the amount of heat loss due to sidewall flex is related to sidewall stiffness. The stiffer the tire, the more the sidewall will heat up for a given amount of flex. It's analogous to taking a piece of string and bending it back and forth. You can do that all day and it will not heat up or flex enough to fail. But, try the same thing with a stiff piece of wire, and it only takes minutes to get it so hot it will fail and break. Your P-rated sidewall is the floppy piece of string; the E-range sidewall is the stiff wire. C-range tires fall somewhere in between.

So, for an LT E-range tire, the sidewall losses at say 35 psi will be much greater than for a P-rated tire at the same pressure, even though the sidewall bulge looks the same. You need to inflate the E-range tire probably to over 50 psi to get the losses down to what the p-rated tire generates at 35 psi. The article I referenced above sort of implies this, but doesn't really state this directly.

It would be instructive to run your tires at 35 psi for 5 miles at say 60 mph, and then stop and immediately measure the sidewall temperature with an IR thermometer. Then inflate to 50 psi and do the same thing. My guess is there would be a significant difference in sidewall heating, and anytime you've got heating anywhere, you're burning extra fuel to do that. I would also suspect that the sidewall heating of a p-series tire would be considerably less than an E-range tire at the same pressure.

The difference between 16 mpg and 18 mpg is less than 1 ounce of gasoline per mile, so it doesn't take a lot of heating somewhere to account for that little bit of gas.

Some of you have mentioned rolling resistance of the tire. This sort of flexing is an important component of that resistance, I think.

 

[heiser]

Well, believe it! Doing ANYTHING that increases the height profile will lower your mileage. The fact that you have a roof rack at all is probably 50% of your problem. As an experiment, a friend of mine removed his factory roof rack and got +1 mpg over stock. Also, it is known that making a truck higher makes more air go underneath it, which obviously takes away mileage. Ground clearance = bad mileage, period. Either you get stuck on every rock or you have no mileage, there is no way around it. For an example, take a look at the new "off road" z71 from chevy. That truck is 8" off the ground when looking at the front air dam, that is the only reason that the mpg increased on those trucks vs. the previous year. Now who in their right mind would attempt any type of trail with a truck that low?

I was getting 17-18mpg after 2/1 lift I noticed NO change in mileage

See, these are the types of posts that had me questioning the lifts affect on mpg because I've seen plenty of posts like this that say there was little to no effect on mpg after doing a lift. It's more so the tires. I realize my lift is a tad higher than normal, and the wind resistance is there, but I think the angle is affecting mpg more than the height.

Also, totally agree on the z71. I've never seen it before but I can't believe they put an off road tag on that.