Poor gas milage suggestions pls.

[cwinma]

My new to me 08 Limited now with 21.5K miles of which 1.5K are mine is only getting 14 MPG city and 16.5 mpg highway. I had it to the dealer for a recall and told them this, they said they checked all systems and nothing showed to cause poor mileage and to keep an eye on it. Anyway, thoughts are a leak in gas tank BUT I would smell and or notice it on garage floor SO my other thought is transmission in that it either is holding a lower gear too long and or not shifting into high gear at speed both causing poor gas mileage?
Thoughts suggestions are appreciated!

[sweeneyp]

honestly a lot probably has to do with how its driven, that is the biggest contributor to low mpg.

Do you drive a lot of short trips (ie so short teh engine never has time to fully warm up/only at operating temps for a little while before you shut it off)? If so during that time the engine is running "rich"(burning extra fuel) and that will murder the mpg on the HL.
You can try a trick to reset the transmission learned shift points to try and improve it. If you pull the negative terminal off the battery and let it sit for awhile it will reset the tranny ECU. Then if you drive it normal (and not drive aggressive) for the next 100 miles after that, it will relearn your driving style. By that I mean if you drive aggressively it will hold the lower gears longer before up-shifting to a more mpg friendly gear, and if you are smoother on the gas it will upshift sooner.
I have noticed though the highlander is very thirsty if driven hard. In the end (no offence meant here) it a lot of times come's down to the driver and how its driven, as that tranny trick isn't going to change a whole lot

[05Moose]

^ That and a whole other list of things can cause poor mileage: Winter blend of gas (containing more ethanol), colder temps, longer driving time while the vehicle is cold (as noted above), tires (as some get worn lower, they don't get as good of mileage and/or tread patches contacting the road may have increased...like with the Dunlops), low tire inflation, and environment you're driving in (like driving in snow will reduce it A LOT).

[cwinma]

Good suggestions BUT most of those problems would need to be in effect to be getting 14/16 which they are not. The - was disconnected from batt during a service date for many hours.

I understand there are many variables here.

Lets take highway driving which is a more constant speed, I'm getting 16 mpg, I just don't get it.

I assume most get 17/20 at the very least.

[05Moose]

Yeah, always get a minimum of 20 mpg on the highway (actually everywhere so far and that's with ethanol year round). Seems like there's always a thread around (both here and elsewhere) where someone is getting poor mileage. I don't recall anyone coming up with a solution. Did your decrease start after the battery was disconnected, when the weather got cold, etc?

[sweeneyp]

05moose, there was another thread (there have been several actually), but I don't remember anyone every having 16 mpg on the highway......I basically got that when I was towing a trailer on the interstate at 70-75mph.....
Do you use the same gas station every-time when you fill up? Could be bad gas (no likely though). When your driving at say 70mph on the interstate on flat ground what does the instantaneous mpg meter read? It could be averaging with the 14mpg city (unless that 16mph was all highway). It should be up around 20-30mpg cruising on flat ground, if its not I would take it to the service manager at your dealer, ask him to test drive it, and tell him to watch the instantaneous mpg meter. He/She should be able to recognize a problem (even if the parts seemed ok when you had it checked). Besides that I'm drawing blanks here

[Subaryota]

Many many variables. In addition to what has been mentioned so far, a few other mechanical issues:

1) Alignment
2) Tire type - what is their rolling resistance ratings? The limited has 19" wheels- very heavy and is likely going to give you fewer mpg compared to HL's that have the 17" wheels.
3) What's your cold tire inflation pressure?
4) Is the vehicle empty or are you driving with multiple passengers and gear
5) Do you leave something on the roof-crossbars
6) Transmission fluid viscosity ratings? Is it as per manufacturer's spec?
7) Engine Oil viscosity rating? At OEM spec?

Driving style
1) I've found 1/2-3/4 throttle acceleration from a stop and quickly getting up the gears to be most fuel efficient. I've found slow starts where the tranny holds onto lower gears longer, to be detrimental to fuel economy.
2) Steady foot and steady speed helps with mpg
3) Anticipating traffic to reduce braking and throttle movements also help
4) Even in the winter, I start the car in the morning, idle for 30seconds to 1min, then drive off. I do not idle for very long.

As a point of reference:
Winter driving with winter gas with 17" snow tires on reasonably light alloy wheels with 5000km on the odo. Cold tire pressures of 35psi all around.

Fluids are OEM spec from the factory (haven't had to change fluids yet)

17 mpg(US) city
23.5 mpg (US) highway - that's with a heavy foot and "deviates from legal limits"

Cheers

[05Moose]

Sweeney, I completely forgot that the limited models have instantaneous and average MPG readouts. Been awhile since we had a vehicle with that. But that's a good suggestion on checking it and pointing it out to the service manager.

[2008HLSport]

I had my tires change some time back on my 08 and got a inch bigger and had the same issue. Make sure the tire size is the same as it came originally as part of the factory set, if not then tire pressure can definitely cause this kind of issue as I have seen on mine vary for 17/32PSi to 23/40PSi.

Another thing you may want o do is take out the charcoal filter from the air filter compartment, there is a thread around that and it seems to improve a bit of mileage around there as well.

If you still have issues then I would recommend going to another dealer/local shop and take a second opinion or have them check it out.

[cwinma]

hummmmm, thanks for the suggestions but it appears I'm going to have to live with an extra 1K in fuel a year. Dealer checks the system and finds no faults, I guess way too many variables to pin it down. Only thing not checked is the alignment but I assume I'd see uneven tire wear if that was out which I do not see.

[Degen]

Have you had the throttle body cleaned? Also, when was the last time the brakes were serviced? If any amount of rust build up is on the rotors or even if the caliper slides haven't been lubricated in a while they could be keeping constant pressure on the rotors causing increased fuel consumption. Warped rotors could also cause this.

[dallen3737]

Alignment is the most overlooked cuprit in loss of the gas mileage. Depending on how off it is you may not see uneven wear in the beginning.

I've also seen a dragging emergency brake do the same thing, especially in colder weather

[TrailDust]

Sweeney and Subaryota both pretty much covered it in my book. Lots of variables to nail down if driving style is eliminated as the culprit. As these guys all know I've been enjoying an average 19 MPG city and 26 MPG highway (at 70 MPH), but I've noticed a mileage hit with my new all-terrain Yokohama Geolanders. I expected that, and I'm still running the numbers to determine my new average mileage which I'll post up when the numbers are in.

[dtown40]

I hope you don't take this the wrong way, but have you checked your parking brake to make sure it is completely released? Just the slightest friction could cause diminished fuel economy, yet not enough to notice lacking performance.

Here is a good site to check out to see what other Highlander owners are getting as far as mileage is concerned, and you can open your own garage there for free, to report your results.

https://www.fueleconomy.gov/mpg/MPG.do?action=garage

[2008HLSport]

Speaking of all these one more thing to check is if your car is equipped with Snow button and if it is used then the mileage does get affected.

I see you from Boston are as well, which dealer do you normally go to?