Fuel Milage Question

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Derick Sullins

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I have a gen 1 2003 4.0l and I get 11 mpg the question is should it be this bad on hwy i get around 14-16. The only things are 265/75/16's and a warn brush guard that I have added it's got the k&n drop in does anybody have any idea if should be better and what I might do to make it better. :cry: It's killing me at $80 a tank!!!!!
 
I have the K&N drop in, 31x10.50 15's and average about 19 mpg between highway and city.

I'd say yours is on the lower side. The 265/75/17s are .5 inch taller than mine. What rear axle gear ratio are you running? I have the 4.10 limited slip, so helps with the take off with the bigger tires. Might try cleaning the K&N and other normal tune up items. I personally run my tire pressures on the high side also.
 
Depending on what reared gears you have the taller tires are throwing your speedo off so it won't read correct. 4.10 gears, it'll be off about 5%, 3.73 gears, it'll be off more and your RPM's will be higher putting more strain on your drivetrain. I have 33's on mine with 4.10's and I know when I'm rolling 60 mph on the dash I'm actually going 64-66mph. I plan on upgrading the gears to 4.56's when I do my SAS, SOA and run 35's to compensate for the taller tires, for now I'll deal with the speedo being off. :banana:
 
Recently after filling up my tank, I avoided accelerating over 2000rpms and coasting when nearing a stop or red light. I slowed down on the highway from my usual 80mph cruising speed to about 70mph keeping rpms at about 2500. My result? I got about 18mpg on that fuel tank versus my usual 14.



I have a Volant intake, 4.10 limited slip, and 255/70/R16 Goodyear Forteras. I may have been using a XCal2 87octane performance tune (sorry, I don't remember).
 
How is your driving style? I would say old grandmothers get better mileage than youngsters, but my grandma used to squawk the tires taking off from a light in her old Plymouth Satellite, so her mileage was probably pretty bad. If you drive better than she did, you should be getting better mileage. I get about 17 nowadays since I'm not on the freeway much anymore, but I used to get 19-20 on the freeway. Mine is a 2003 with 3.73 gears and 245-75R16s.
 
I used to have an '05 with 3.73 gears and 265/75-16's also. The speedo was off by about 10%. If I added 10% to the miles when calculating mpg then it was only slightly worse than stock.
 
in order to get an accurate reading, you need to find out the exact difference in tire size, and determine how far off your speedometer/odometer is off.



Also, consider that most speedometers/odometers come from the factory reading a little bit higher than the actual mileage. So your speedometer may say you are driving 60 MPH but your true speed may only be 58-59 MPH



One of the new tools I purchased for my Toyota Highlander is an UltraGauge. It only cost about $59 from UltraGauge and simply plugs into the OBDII disgnostic port under the dash. It tells you more info than you will probably ever need to know...:grin:





If gives you Avg MPG and Instantaneous MPG that changes about every second...great for seeing exacly what kind of driving give better or worse gas mileage. The added feature is that you can calibrate the unit to match your tire size. You simply stop at a mile marker along the roads and Interstates...set the gauge, then drive to the next marker. For greater accuracy, drive past multiple markers. Stop at the mile marker and tell the UltraGauge how many miles you drove. That calibrates the UltraGauge and it now knows the adjustment factor to apply to all your mileage readings, and you don't need to even do any calculations.



Other features include accurate temperature readings, 2 separate trip readouts, CEL codes and the ability to clear any Check engine codes. Depending upon make and model of vehilce it can even measure fuel pressure, how much gas is in the tank, etc...just depends upon what sensors your vehicle has.



...Rich

 
Derick,



Your gas mileage is close enough to the norm to be acceptable, maybe a little on the low side.



Your driving style more than anything will influence your gas mileage.



If you do jack-rabbit starts and are the type that races up to stop signs and lights only to have to slam hard on the brakes to jolt to a stop then you will get the kind of gas mileage you are talking about, or worse.



14 to 15 around town, highway in the high teens are about the most anyone can hope for with the ST. Some will talk about the snake oil and devices they have put on/in their ST and how they get 20 around town and 25 on the highway, but I am 100% skeptical of such claims...and even if they are getting such results with THEIR driving style, it doesn't mean you will.



There's not much you can do to get better gas mileage, IMHO, except slow down, coast more, slow starts, etc.. Any money spent to try to get better gas mileage is better spent putting more gas in the tank, IMHO.



The ST isn't a gas sipper.



TJR
 
Completely stock, 265 tires, 5 speed stick, 17 mpg around home 20-25 on highway depending on 60 mph or 80 mph. Thats on 87 corn fuel.



Better on 90 octane ethanol free.
 
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The 5 speed may be helping you out on your gas mileage, drpertz. I say that because most people that actually drive a 5 speed effectively tend to get to the higher gears as quickly as possible and do a lot of coasting, especially where the lower gears might be otherwise downshifted into. I suspect that helps fuel efficiency.



TJR
 
According to my Ultra Gague, I was getting 117 MPG at one point yesterday... :driving:











Yes, it was downhill, and I had a 25mph wind at my back... but it sure was nice while it lasted!! :grin:
 
Dave,

Yes, I know the feeling.... I have gotten over 150 MPG (Instantaneous MPG) for a few seconds when I let off the gas from about 70 MPH going down hill.:grin: Makes me wish that everywhere I drive was always downhill...both ways...:bwahaha:



...Rich
 
Downhill mileage rules.



I don't know how many MPPBJ (miles per PBJ sandwich) my old "go cart" got, which was essentially just a home-made coaster soap-box cart that we took down this long, paved driveway at our highschool. The race track was 1/8 mile long, and we would go down it dozens and dozens of times as a kid.



Best fuel economy I ever got.



Oh, and even then we knew that "rubbin's racin."



TJR
 
In addition to fixing your speedo issue; I recommend switching to synthetic oil (tranny & diff too), remove the air silencer in front of your air box, a Zabtek throttle body & a Y-pipe with a single-in / duel-out muffler (of your choice).



I recently switched to AmsOil Extreme Performance & Autolite XP spark plugs, and I am now able to shift (manual shifter) at lower rpms. I plan on getting Taylor-Vertex Street Thunder wires to compliment the plugs after I have my body mount bushings replaced.

:banana::driving:
 
I agree with Rodger about the use of synthetic oil in the engine, transmission, and differential. They do reduce friction and in the engine you can uses a thinner viscosity to improve milage while still giving maximum protection.



You don't have to buy the exotic synthetic oils, especially if they cost more and are harder to get locally. I have used Mobil-1 that you can buy at any WalMart and it works great.



Of course thee is a limit to what synthetic oils can do for gas mileage and If you manage to pick up about 1 MPG you have done good.



I am opposed to adding a lot of speed equipment for the sole purpose of improving mileage. Generally the higher cost takes years to ever pay back from gas savings, and if you like to put your foot into the gas pedal, adding speed equipment just increases that temptation.



Add speed equipment if you want to go fast, but if you want to save money on gas, don't spend too much money on speed equipment in hopes to save gas...in the long run it rarely ever saves you anything.



The best fuel saving device is the nut behind the wheel...lol If you want to spend money on something that has a definite pay back in better MPG, get something like a ScanGauge or UltraGauge. They don't modify the engine or make any guarantees of better fuel mileage. What they have is Average, and Instantaneous MPG readouts that can show you exactly what kind of good driving habits will save gas and what bad driving habits can waste gas.



I bought an UltraGauge about a month ago to use in my 2002 Toyota Highlander. The first week I learned my existing gas mileage and exactly what driving situations was helping and what was hurting my gas mileage. The following week I improved my mileage by 1.2 MPG with some realtively minor changes to my driving. Inspired by what I learned, I have been watching my driving habits very closely and have managed to pick about another tenth of a MPG each week. I lost about 1 tenth of a MPG over the past week because of the windy weather here and it does make a noticable difference in gas mileage especially with the poor aerodynamics of trucks and SUV's. The Ultragauge only cost about the same as a tank of gas $60 and I can already see an improvement in MPG, so I know it will pay for itself in a reasonable amount of time, and I can always transfer it to another vehicle if I get rid of my Toyota.



...Rich



 
Gotta agree with the ScanGauge recommendation.



Monitoring the MPGs both instantaneous and average really helps me improve my MPG. My experience has basically been analogous to Richard L's.



The ScanGauge also showed me that after the 87 performance tune, my mpg tends to be better as I drive around 65, as opposed to my previous method of driving around 60.



Recently a disturbingly low rating on instantaneous MPG under conditions I drive all too often (commute) clued me in right quick that my tire had sprung a leak during the trip.



Though what really does suck is that a couple of really good highway trips on a tank of gas, which tend to get me 20-23 mpg (per scangauge), are more than negated by a few short in-traffic commutes.
 

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