oardila99

Hi all, Thank you for reading,

I have a 2003 GX470, 97k mi. I have been hand calculating my fuel economy and I have been getting 13.7-14.1 mpg in the city. The computer says avg mpg is 16.8, but I just wish happily that those numbers ever realize.

I drive like a total grand mother with white hair and all.

I coast down the road annoyingly when I see lights turn red far ahead of me, letting the car's drag slow me down as much as possible, in an attempt to maximize the use of my kinetic energy.
I accelerate super slowly (that i'm cool with given the pleasant smoothness of the GX),
I use 87-octane gasoline.
I use the cruise control every time that I can, and as I said, I disangage it way before redlights, or possible slow downs. Additionally
I have all 4 tires inflated to 42psi (overinflated), and altough I always practice this unusal driving (it must look pretty retarded to other drivers) I still get 14.1 mpg! I need help urgently!

Things that I have not tired:
1. Alignment: How bad can the mpg suffer if the vehicle is slightly misaligned? I get pretty decent tire sqeaking when tuning in parking lots and such. Is this usual in the GX? if not I may be out of aligntment.

2. Using Fuel System Cleaners: I have never poured any thing in a funny looking bottle into my fuel tank. Has anybody poured one or two of these and gotten better fuel economy?

3. K&N Air Filter: I have read in other posts of people using K&N filters, but some agree, and some disagree on the benefit. Has anybody noted a definitive improvement in fuel economy on the GX by using K&N filters?


The GX470 manual says it holds 23 gallons, but I am able to put in 24.3 gallons of 87 octane gasoline everytime. How? I keep putting in gas very slowly after the pump stops, until I see the fuel come up the pipe and approach the fuel cap; I literally fill it to till it can take no more. From this super full tank of 24.3 gallons, I get 343 miles on the trip odometer, for a grand 343/24.3=14.1

For those attempting the same calculation, note that the GX has about a gallon of reserve, thus it will drive ~15 miles (granny style) after the computer reaches 0 in the range. I have never ran out of gas, so I don't know what exactly the reserve is, but I usually don't push this this reserve beyond 12 miles.

PLEASE HELP! MY MPG is killing my budget! HELP HELP HELP!
Any tips would be greatly appreciated, specially if I realize city mpg's in the 16's

Thanks a lot!

OA

ALAN553

first off, you should not be topping off the tank like that. that could account for your poor milage and calculatins.

http://www.epa.gov/donttopoff/

oardila99

Thanks for the heads up Alan; that is an important point, and I sure did not know about it. The keypoint here is that overfilling the tank can cause damage to the fuel system:

""Toyota’s Hybrid System Diagnosis Technical Training Manual for the Fuel and Evap System and found the following information about overfilling:

Trying to force additional fuel into the tank pushes excess fuel into the EVAP system. This may cause an EVAP DTC and may even require the replacement of some EVAP system components"

I am sure that this is something that most people don't know about.

I found additional info on that here: http://www.ecobuzzla.com/green-drivi...your-gas-tank/

IF ANYBODY ELSE KNOWS HOW TO INCREASE FUEL ECONOMY ON THE GX, ALL CONTRIBUTIONS ARE GREATLY APPRECIATED,

OA

gsobol

Sorry Oardila99, but this is a BIG, HEAVY truck, being pulled by a 4.7L V8. There is no magic pill here. 13-14 MPG is on par with what this truck does in the city. It can be a bit better on the highway. I was able to get approx 20-21 MPG on my cross country trips, but the stop and go traffic of the city will kill your MPGs pretty quick.

Oh, BTW, on board computer is VERY optimistic when it comes to calculating your MPGs, so by hand calculations will give you a more accurate results, as you already found out.

Booyah

Your not going to get much better period! maybe drive it harder, it likes it

I drive my 08 GX I would say somewhat Agressive, I get to speed quick, hardly ever go the speed limit lol.. most of my drive is in the city and when im on the highway I do 75-80. I constantly get 16MPG. Open highway runs I can get into the low 20's.
I also Fill my tank to the TOP, to where I cannot get any more gas in it, Ive done that for 30 years to all my cars and never had any ill effects.

oardila99

All these are good considerations. Booya, it sounds like you drive your GX harder than I drive mine. These are all good contributions, as I may try different driving habits and see how the fuel consumption behaves. Question. the MPG that you report as 16 city, is it hand calculated? or it's per the onboard computer? - I've done the "fillup till you see the gas" for a while now. I even did it in my previous car, and nothing ever happened either. Although it is nice to get the extra range between fillups, I did some research and found literature by Toyota saying that it in fact MAY cause damage.

BTW: my current Fuel Efficiency, as I said before is 14.1 city, and ~16 highway @65mph.... you are reporting 16city/low 20's for highway. Might it be a problem in my truck? - I'm starting to give serious thought at it probably being improperly aligned. Tires are inflated to 42psi.



Thanks for your reply.

gsobol

There is a difference in engines to consider as well. Toyota has upgraded the 4.7L in '05 with VVT-i (variable valve timing with intelligence [debatable]). The new engines are more powerful and slightly more efficient due to multiple factors VVT being one of them. Generally '05 and newer gets approx 1-3 MGPs more than the older '03-'04 models, but you can't throw in the supercharger in the '05 and newer . Ahhh, that's probably not something you are looking to do since you want to increase your MPG's not make them disappear in the cloud of tire smoke .

Booyah

Yea thats the ON board caculation! I will fill up and do a hand caculation just to see. I dont "race" my GX but I dont drive near as conservative as you either..lol

Yea after the nozzle clicks off--you can get easy several or more gallons of gas in the tank--We need alll the extra we can get.lol

BLUEGXLVCR

My situation is a bit nuts. I have a 2005 I bought about eight months ago and I think either it sat quite a bit or had not broken in yet. It only had 19K miles when I got her. I now have 23K miles on it, towed a boat a few times, and a few sea-doos. Now my mileage is 16-17mpg by hand. Not great, but I'm that driver that upsets Grandma. I'm all over the gas pedal and barely any freeway.

I am going to drop a K&N filter in it as it's only $50 of test. I use brand name gas, Shell or Chevron and only 89 octane. I don't care about my MPG as you can see in 8 months I have only driven 4K miles and that includes a trip to San Diego from Las Vegas.

ALAN553

Caution on the k&n air filter, first, it will not improve anything that you can measure on a GX 470, second, the oil from the filter has been know to dirty the MAS (mass air sensor).

A mass air flow sensor is used to find out the mass of air entering a fuel-injected internal combustion engine. The air mass information is necessary for the engine control unit (ECU) to balance and deliver the correct fuel mass to the engine. Air changes its density as it expands and contracts with temperature and pressure. In automotive applications, air density varies with the ambient temperature, altitude and use of forced induction and this is an ideal application for a mass sensor. (See stoichiometry and ideal gas law.)

There are two common types of mass airflow sensors in use on automotive engines. These are the vane meter and the hot wire. Neither design employs technology that measures air mass directly. However, with an additional sensor or two, the engine's air mass flow rate can be accurately determined.

Both approaches are used almost exclusively on electronic fuel injection (EFI) engines. Both sensor designs output a 0.0–5.0 volt or a pulse-width modulation (PWM) signal that is proportional to the air mass flow rate, and both sensors have an intake air temperature (IAT) sensor incorporated into their housings.

When a MAF is used in conjunction with an oxygen sensor, the engine's air/fuel ratio can be controlled very accurately. The MAF sensor provides the open-loop controller predicted air flow information (the measured air flow) to the ECU, and the oxygen sensor provides closed-loop feedback in order to make minor corrections to the predicted air mass.

BLUEGXLVCR

What he said... I'll use stock cause as I mentioned, I'm not worried about my mileage. Oddly enough, it's better than my wifes ML350. Go figure!

oardila99

ALAN, Yeah, that is true. Id like to find out which mass flow sensor is used in our GX's. I imagine that the hotwire type could easily be, due to it's fundamental simplicity. The only reason why it wouldn't be, that I can't think of, is the response time of it, although I doubt this being an issue as the filaments used in this type of sensors are super thin, and respond almost instantaneously. I doubt they use Vane or Vortex type sensors in our GX's though I'd like to find out. I'll be on the lookout for reports of mass flow sensor issues due to K&N's

Thanks for the input. OA

ChrisK

iTrader: (1)

I use AFE PRO Dry S air filter.

oardila99

WHAT? - I was considering a CLK350 cabrio, If some plans in s.Florida were to realize, in addition to the savings in gas. Your ML and the CLK use the same engine! I might as well keep my much liked GX and be better off that way! - That's amazing. Additionally, I have not been much impressed with an MB C-class that my father has. Hondas and Toyotas, are my top choices - hence my gas station-buddy GX. I'm starting to get to know the Chevron guy's family story and all, due my frequent-customer status at the corner Chevron. They moved to the U.S 7 years ago, have two daughters, etc... Now I know why he got happier than my gf when I got the GX. In any case I really like the GX, but I need HELP with the fuel economy.

TO ALL READERS - ANY OTHER INPUTS on successful mods/tricks/ or other things performed to add at least 2 mpg to the GX? - THANKS!

oardila99

Good. Did this help your fuel economy?