MPG going DOWN

[Erkelbot]

I've read a few threads on this, and I'm trying to get to the root of the issue... Thanks in advance for indulging me.

My 2015 4Runner TEP has about 1200 miles. All stock, except I swapped the tires for AT/3s. Since then, my mileage has suffered tremendously. When I had the rubbish H/Ts, I was bordering on 19MPGs. Now I'm lucky to get 16.5MPG. I drive 75-80% highway, and always abide by the dumb little ECO light (under 2500 RPMs at all times). The temp has been consistent since the tire change. I've reset the stats in the computer several times. After doing so on the HWY, I get 18ish... The new tires are MAYBE 2 lbs heavier than the old ones, and are not the LT versions...

By all account my MPG should be going up (or at least neutral), not down. What gives? My old 3rd gen with AT3s was getting better MPG and it was carrying around a MegaWarrior basket on top.

Also, I'll check on tire pressure, but I'm fairly certain that the tire shop filled them up to recommended PSI a week ago when they were swapped out.

Any ideas? Seems pretty far off from the sticker on the window of 17-21, but perhaps I'm being too optimistic.

Side note: As I began to think about the eco light, and augmenting my driving behavior to keep that light green I got to thinking that perhaps that's a part of the issue. Theoretically longer periods of lighter load on the engine (ie - slower acceleration to reach speed) over short bursts of acceleration may affect MPGs. I think I may turn the light off and start driving the way I feel like driving to see how that changes things. I've already experimented for short times, but never stuck to it long enough to see if it make a measurable difference. Has anyone tried this to validate this hypothesis?

Thanks.

 

[AirspeedX]

Sounds normal to me. When I put my General Grabber AT2's on, I lost a bit of economy as well. But they can tear up the trails!

I turned the ECO light off a long time ago. If you're really looking for the numbers, base the data off fill-ups and recorded mileage vs the computer.

Don't worry about it too much. Fuel economy is what little 4-cylinder cars are for.

 

[CSix]

While big tires gulp gas, winter gas doesn't do your mileage any favors. Here in Colorado they increase the ethanol content during the winter and gas mileage definitely suffers. Does your gas formulation change with the seasons?

 

[Rocky5000100]

My mpg goes down every winter. Normally I get around 18.5-19 in the summer, but winter is normally 15-17.5. I track every fill up in the Fuel Log app. I attribute the mpg loss to the winter blend of gas, higher rpms while the engine warms up, and doing lots of donuts in the snow.

 

[JayceeP]

My consumption increases 10% (almost 2mpg) as soon as Nov 1st rolls around. It drops 10% by end of April. Winter gas. It hasn't even been really cold yet either. Some tanks will even dip down near or even below 15mpg from time to time.

16.5 on the highway is pretty bad though. You should be able to get 17+ in flat/calm conditions. I drove a 2 hour highway trip each way last weekend and got about 16mpg. 75mph, hilly, windy.

 

[Jayhawk5G]

It's been mentioned previously, but I agree it sounds like a combination of the tires and winter blend gasoline.

 

[manofsteele2003]

My mpg goes down every winter. Normally I get around 18.5-19 in the summer, but winter is normally 15-17.5. I track every fill up in the Fuel Log app. I attribute the mpg loss to the winter blend of gas, higher rpms while the engine warms up, and doing lots of donuts in the snow.

Yes agreed. I haven't had my 4runner through a winter yet but my FJ was the same way. Summer was about 18+ and winter dropped to around 16 or less. Winter fuels have a lot more additives in them for the temperature drop.

 

[Erkelbot]

Yes agreed. I haven't had my 4runner through a winter yet but my FJ was the same way. Summer was about 18+ and winter dropped to around 16 or less. Winter fuels have a lot more additives in them for the temperature drop.

Thanks guys -- good to hear from some nordic folks. Sounds like a function of the change in blend at the pump. I'll keep an eye on it and start me an .xls to track over time. My guess is it'll bump up once they fix the fuel in spring, but we'll see. Much obliged.

 

[manofsteele2003]

Plus you're still breaking in your truck so to speak, you should see a slight increase the more miles you get and after your first oil change.

 

[Donkey]

I usually see a decline of about .5 MPG right around the time winter blend fuel is introduced. As the temperature drops gasoline can be manufactured with a higher RVP (Reid vapor pressure.) This is usually accomplished by adding more butane, which burns more quickly and fuel economy may drop as a result.

I've been tracking my fuel economy from day one, something I've done on every vehicle owned. I did see some drops during the first few thousand miles that did not make much sense, perhaps the engine goes through some kind of learning sequence. I use the eco light :hiding: and try to stay below 73 MPH and avoid excessive idling. At 20k miles I am sitting right at 19.0 MPG via fuelly (same pump and technique from two different stations for 90% of fill ups) with the worst tank of 17.34 and 17.98 coming in a January and November, both winter blend months. 70% of my driving is city.

Most people don't report that great of a drop going from the OEM tires to P AT/3s. Perhaps it is some combination of the tires, winter blend gas, sub-conscious winter driving techniques, increased use of part time 4WD, more idling and short trips in the colder temps. I'm sure it will pick back up soon. I filled up for $2.24 this morning which was pretty awesome too.

 

[badhabits]

I am also running the Cooper AT/3 tires, and just got back from a round trip from Va. to San Antonio TX. a distance of 2700 miles. My over all millage was 20.2 using the miles divided by gallons, and not the on board computer. I have made similar trips in the past during the summer and yes I have gotten better mileage. I do not think that your tires are the major loss on fuel economy. I also noticed that I got better mileage in the mountains of Tennessee and Virginia than in Texas and Arkansas, go figure.

 

[1engineer]

I've read a few threads on this, and I'm trying to get to the root of the issue... Thanks in advance for indulging me.

My 2015 4Runner TEP has about 1200 miles. All stock, except I swapped the tires for AT/3s. Since then, my mileage has suffered tremendously. When I had the rubbish H/Ts, I was bordering on 19MPGs. Now I'm lucky to get 16.5MPG. I drive 75-80% highway, and always abide by the dumb little ECO light (under 2500 RPMs at all times). The temp has been consistent since the tire change. I've reset the stats in the computer several times. After doing so on the HWY, I get 18ish... The new tires are MAYBE 2 lbs heavier than the old ones, and are not the LT versions...

By all account my MPG should be going up (or at least neutral), not down. What gives? My old 3rd gen with AT3s was getting better MPG and it was carrying around a MegaWarrior basket on top.

Also, I'll check on tire pressure, but I'm fairly certain that the tire shop filled them up to recommended PSI a week ago when they were swapped out.

Any ideas? Seems pretty far off from the sticker on the window of 17-21, but perhaps I'm being too optimistic.

Side note: As I began to think about the eco light, and augmenting my driving behavior to keep that light green I got to thinking that perhaps that's a part of the issue. Theoretically longer periods of lighter load on the engine (ie - slower acceleration to reach speed) over short bursts of acceleration may affect MPGs. I think I may turn the light off and start driving the way I feel like driving to see how that changes things. I've already experimented for short times, but never stuck to it long enough to see if it make a measurable difference. Has anyone tried this to validate this hypothesis?

Thanks.

In 1200 miles you only know what your mpg is for a very short period of time.

Read this http://www.toyota-4runner.org/5th-gen-t4rs/157694-how-your-miles-empty-range-indicator-operates.html if you are using your on board miles to empty or your instant mpg screen. This gives a short explanation on why you see what you see.


Read this as a primer for the explanation of winter gas http://www.toyota-4runner.org/5th-gen-t4rs/102219-winter-gas-explained.html as it will help you understand the differences and why we even run winter gas.

Once you get 10,000 miles on it you will be able to see a better trend than what you see now.

 

[High_Country]

A small, but not-yet-mentioned point to consider: we're all assuming by 'swapped the tires' you stayed with the stock size. Even so, I wouldn't be surprised if the circumferences were different (greater on the AT/3's) which would yield lower calculated mpg's than reality. Not much mind you - a couple percent at most. Just something to think of.

 

[Erkelbot]

A small, but not-yet-mentioned point to consider: we're all assuming by 'swapped the tires' you stayed with the stock size. Even so, I wouldn't be surprised if the circumferences were different (greater on the AT/3's) which would yield lower calculated mpg's than reality. Not much mind you - a couple percent at most. Just something to think of.

265/70R17s. I stuck to stock, since the 275s were significantly more expensive and would only further affect the MPG.

 

[rydr1]

Swapping tires can affect MPG even if its the same size. Better traction will yield lower MPG, more aggressive tread patterns will lower MPG.

I'm didn't looking up the specs, but by guessing your stock tire tread may be 10/32 new and the AT3 may be 16/32 new.

 

[dproberts]

If you're wanting to track MPG have a look at Fuelly if you have a smart phone. There's probably some other free smart phone apps too.

 

[NoDak]

stats

.

 

[03_4x4Runner]

Different tires but probably the same results. Tires and Fuel Economy - Four Wheeler Magazine

 

[Osmith]

I second fuelly I have kept my stats from that sense day 1.

Fuelly says I am at 20.1
4Runner says 18.3

 

[Engineer]

Doesn't help you but my truck tells me 15.9 :beer: