Why the MPG drop?

[jjdbike]

Hi folks.
I got my 2011 4Runner SR5 at the beguining of Jan. It got 12-14 mpg. I lifted 2 1/2” front & 2” back w/ UPA’s and dif drip, 285 AT’s w/ 17 / 8” RN wheels. etc. W/ the newer lighter wheels and the Discoverer AT3W at 38 PSI my MPG went up to 16 - 17mpg. I also had my trans flushed at dealer (long story). I figure it’s the ligher wheels & my pervious tires were knobby mud tires, plus I’m driving more carfully, accerating slower and more evenly. I got a new battery (Interstate MTy34R AGM ahich is Heaiver). Got my headlights, high beams & OEM fogs rewired w/ better gague wire, relays & fuese. Installed high performace bulbs. Got auxilliary fog lamps installed (hella). Also just had front & rear diffs & transfer case serviced along w/ oil change, injector cleaning and throtle body cleaned at dealer. Then I got coolent fiush & new power steering fluid. My MPG droped to 10 mpg from 16 mpg. What could be the cause? I’m worried. Are there any diagnostics I can have done? I don’t trust the dealer’s service dept and won't go back again. Could they have gummed something up or done something wrong? Bad gas?
I appreciate any and all ideas & suggestions. I’m more interetsed in good performance and longevity then simply getting good MPG. From 16 to 10 is significant.
thanks in advance.
JD

 

[Jhalko]

Are you hand calculating or using the readout? Given all that stuff you run down I wouldn't trust the readout at all. But I will go out on a limb and suggest the lighting changes probably didn't impact mileage. Haha.

Once I bolted on my first mod I stopped watching mileage, but even with all the heavy crap I have I average 17 around town (with RTT on). I accelerate a lot slower than I used to though, that seems to be my biggest factor.

 

[jjdbike]

Thanks for the reply. You have way more and heavier more than I. Yes I'm using read out. I know the larger tires make the odo inaccurate but only by a very small margine. I watch and have reset the computer many times and it's generally consistent. It read 12-14 when I took delivery in Jan at 55k. Lift, wheels and trans flush it read 16-17. Lights and new battery along w/ a ton of maintainace above and beyond factory recommendations and now it consistently reads 10mpg at 61k. What could be at play? Any recommendations?
JD

 

[Simpleman74]

I get 17/18 and I am running heavy. lifted, tires, Gobi etc..... Isnt there a way to reset the vehicles memory by disconnecting the batt and letting it relearn?

 

[JohnJerk]

With the lift and 285s, I'd think the computer readout would give you something like 10-13 mpg. How many tanks of 10 have you seen? Do you tow?

 

[Jayhawk5G]

Most people running 285's with up to a 3 inch lift see 15-17 mpg. I suppose aggressive driving or driving in mountain areas with lots of elevation change could lower it more, but 10 mpg seems hard to believe as accurate.

When you unplug the battery it wipes your running mpg average and starts over, so it may take awhile to reflect an accurate reading. Like others suggested I would hand calculate your mileage as it's likely much higher.

Final reference, before purchasing my current 4Runner I had an 05' Jeep Grand Cherokee with Quadra-Drive 2 and the 5.7 Hemi V8. I got 11.5 mpg no lift, with an AT tire which again makes 10 mpg hard to believe.

 

[salong53]

Although you listed a ton of variables, the biggest things that will cause gas mileage inconsistency are where you drive and how you drive.

I can't get better than 15mpg on my 10 mile trip to work if I reset my computer before I leave. I can get over 20mpg taking the same route going the opposite direction. Obviously the difference is the elevation change and the traffic.

Just change your display to the digital speedometer and forget about gas mileage in your lifted, modified, body-on-frame SUV. That's what I'd do.

 

[jjdbike]

Although you listed a ton of variables, the biggest

Just change your display to the digital speedometer and forget about gas mileage in your lifted, modified, body-on-frame SUV. That's what I'd do.

Thanks for all of the input.
Salong, yes but w/ all of these people running heavier than I getting much better MPG, I’m concerned something may be wrong.
JD

 

[FrontRange4Runner]

I'm not sure how you are calculating things, but it may be a bit off.

 

[tamerunner]

There's only 2 times I have ever seen 9-11 mpg on our runner. One was pulling a trailer down the interstate in sport mode doing like 80 to keep up with traffic and the other was short trips in the mountains on switch backs keeping it in sport mode to keep the tranny from shifting so much. Otherwise 15-16 is normal for my wifes commute and we can get around 17 on trips. No over sized tires but gobi rack and Thules I've been to busy to take off yet this year, guess I should just leave them on at this point.

 

[RonJR]

Getting useful gas mileage numbers requires some attention to detail, and observing the mpg meter in the car isn't a necessarily good way to do it. Here's the best way to do it really well.

- Calibrate your odometer: Drive down the interstate for at least 10 miles, noting your odometer reading to the nearest 1/10th at the first mile post and at the last. Do the math to figure out your odometer error. E.g., if the odometer says you went 10.6 miles over a 10 mile stretch, the odometer has a 6% error (high).
- Pick a gas station and a pump. Always fill up at the same place, same pump.
- Each time you fill up, insert the nozzle the same distance into the tank and stop filling when the auto shutoff trips. Note the gallons and the mileage on your trip odometer. Reset the trip odometer.
- Calculate mpg by MPG= (Miles/odometer error)/gallons. Example:
Odometer is 6% high. Therefore, odometer error = 1.06
Miles = 250
Gallons = 15
MPG = (250/1.06)/15= 15.72 mpg.

Do this over several tanks in various conditions. I know this is painstaking, but anything less analytical turns into guesswork and hearsay really quickly.

Also, note that the MPG meter in the 4runner calculates a running average since the last time you reset it. So, if you don't reset it for a couple thousand miles or so, your recent driving conditions have almost no effect on the reading, since recent driving is being averaged in with what you did in the distant past. If you've made a significant change either in the vehicle or your driving habits, you need to reset the MPG meter to allow it to base its information solely on recent activity.

Edit: I had the MPG formula wrong for the odometer correction. I should have divided rather than multiplied. It's corrected now.

 

[BlackWorksInc]

Additionally if you compare your current tire size with factory tire size you'll find your correction value for calculating MPGs. You might not think it's much but that combined with the inaccurate way the "Optimism" meter seems to read fuel efficiency could be a variable affecting things.

For example I can't remember where in the mounds of Toyota FSM crap for various vehicles I read it in, but part of the variables that the "Efficiency" meter looks at is #1 Injector Pulse Width; which is commanded by the ECM. So if the ECM thinks it needs a longer pulse width, that would make it think it's using more fuel, but honestly that's just one of dozens of various data points the vehicle uses to guess how much fuel it's using.

 

[sting555]

My computer readout is consistently around 13 mpg