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Discussion Starter · #1 ·
maybe this belongs in another section, but i figure with the mods done specifically for off-roading, it may apply here.

I have owned my tundra since new. When it was stock, it got about 315 miles on the odometer before the gas light would come on. Assuming i would fill up about 330, id put 24 gallons in = 13.75 miles per gallon. over time, i have done a number of mods. I have noticed a significant decrease in my mileage. 1 mod i had never done was a speedo recalibrator. I finally did this, assuming id get a better picture on my mileage... its WAY worse then i ever imagined. the speedo is within .5 miles of GPS. at the half way mark on the gas gauge, i had about 110 miles. Assuming thats accurate, thats 220 miles to empty or 9mpg.

now the truck has nearly 100K on it. i have 285's, regeared to 4.56. the only engine mod is a flowmaster (about 5K miles ago). i have done regular maintenance. i have a clean air filter, i cleaned the throttle body, and MAF. body mods like my roofrack and shell have been on there since new. i had an 02 sensor issue (upstream), it never tripped a code, but was pointed out to me by one of the mechanics thats frequents this board. i replaced them at about 70K. i have had the lockers in for about 25-30k miles now. there are new spark plugs

my driving style has probably improved over time... meaning im not always hard on it any more. my commute has not changed since the truck was new. the mix of highway/city driving has not changed either.

are you guys with similar mods seeing this type of mileage?
 

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Discussion Starter · #2 ·
Re: gas mileage with all the mods

typo in the title... i cant change it. should read Gas Mileage with all the mods.
 

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My Ford went from 15 to 8MPG. Lift, Tires, Intake, Exhaust and a lighter foot.

I have not modded my Tundra much just a muffler. And I get average 18-19 and do not plan on lifting this one so??? BUT I usually lift everything I own so possibly in the future.
 

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I get 10 in the city, 15 or so on the highway...and I do drive like an *** most of the time...
 

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maybe this belongs in another section, but i figure with the mods done specifically for off-roading, it may apply here.

I have owned my tundra since new. When it was stock, it got about 315 miles on the odometer before the gas light would come on. Assuming i would fill up about 330, id put 24 gallons in = 13.75 miles per gallon. over time, i have done a number of mods. I have noticed a significant decrease in my mileage. 1 mod i had never done was a speedo recalibrator. I finally did this, assuming id get a better picture on my mileage... its WAY worse then i ever imagined. the speedo is within .5 miles of GPS. at the half way mark on the gas gauge, i had about 110 miles. Assuming thats accurate, thats 220 miles to empty or 9mpg.

now the truck has nearly 100K on it. i have 285's, regeared to 4.56. the only engine mod is a flowmaster (about 5K miles ago). i have done regular maintenance. i have a clean air filter, i cleaned the throttle body, and MAF. body mods like my roofrack and shell have been on there since new. i had an 02 sensor issue (upstream), it never tripped a code, but was pointed out to me by one of the mechanics thats frequents this board. i replaced them at about 70K. i have had the lockers in for about 25-30k miles now. there are new spark plugs

my driving style has probably improved over time... meaning im not always hard on it any more. my commute has not changed since the truck was new. the mix of highway/city driving has not changed either.

are you guys with similar mods seeing this type of mileage?
Honestly its your gears

4.56 with 33's maybe 32's with the tread wear
With my 3.91 and 305/70/16's I am getting 16 mpg. min. - 19 mpg max
I may be one of the lucky tundra owners.
Less RPMs means less gas being used with 3.91's and 33.1"s, I can never figure it out why everyone gets crap mileage with their 33's and stock gears.
I did get worse like 9-12 mpg. until the ECU adjusted to my different RPM band now and distribution of toruqe in the engine, and overall driving.

Gear charts indicate this Figuratively. Better mileage , NOT worse, adding your 4.56 gears with 285's. Sure ......probably accels fast, but what RPMS do you run at?

Also have you ever gotten good or better mileage with the 4.56 gears before your current problem at hand? You didn't state how long you've had the gears on. If you just got them on the computer (ECU) needs to adjust to all the new distribution of torque throughout the RPM band of 700 RPM's all the way to 5200 RPMS. This means learning and until the ECU adjust your mileage will SUCK!! as will your gas tanks rate of emptying out.

Give it time.

My 245/70/16's (29.5" tire new) with stock 3.91's: almost the same rpms as 33's and 4.56 gears (80 rpms less) according to gear charts.
my ScanGauge II that is tapped into the OBDII that is attached/linked to the ECU as realtime engine operations/and parameters. registered 2200-2300 rpms at 60mph. The truck was stupid fast. And it also sucked gas very fast.

The engine also could go to 5200 rpm's very quick unlike 33's and stock gears. Now with my 33's adjusted for 60mph I run 1900 rpm's or less.

Here's a tip: Get some bigger tires maybe. It may cure the problem some.
This or you have another problem to search out.
 

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Discussion Starter · #6 ·
i have had the 4.56 for about 25-30k miles. i had the larger tires with stock gearing for aboout 15k miles... then i regeared. i couldnt get an accurate handle on my mileage, because my speedo was never calibrated.

ill have to check, but @ 75mph, i swear the tach isnt much over 2k.
 

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Re: bad mileage with all the mods

Hey buddy, with my setup (315's) and running 4.88's I get right about 13 mpg in my regular 17 mile (each way) commute. It's virtually all on surface streets. The best I've done on the freeway at a cruise control 70 mph was 14.9 mpg. I try to drive fairly easy on the throttle, but sometimes I just gotta go! :clown: Here's my tach readings for various speeds (with the Superlift speedo recalibrator and speed confirmed by hand-held Garmin GPS):

60 mph = 2,000 rpm
65 mph = 2,200 rpm
70 mph = 2,400 rpm

Towing our 26' travel trailer at 55 mph to 58 mph returns 9 mpg with OD turned off. Then I'm tacking about 2,600 - 2,800 rpm.

Just curious, are you running any synthetics? I'm running Mobile 1 in my engine and did a complete flush and fill last year with Amsoil for the tranny. I'm NOT running synthetic in the diff's because in the earlier model Tundra's, the axle seals were not designed for it. Some folks are running it without leaks, but I didn't want to take the chance.

Spark plugs? How do they look?
 

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Are your mileage calculations corrected for tire size and gear ratio?

Steel or aluminum wheels? (Al is better)

Tailgate down or up? (Up is better)

Mileage decreases with larger tires because the rotating mass has increased and it takes more fuel to get those tires rolling...same thing happens with larger rims, or switching to steel rims from aluminum. You'll see the same thing happen if you switch to a wider rim as well. The more stop/go driving you do, the lower your low end mileage will creep...high end seems to be about 17mpg on my truck, but it can get as low as 11 if I'm forced through rush hour on a hilly road.

Higher gears (low ratio number) and large tires does not mean better mileage. It might look like fewer rotations per mile = fewer cycles per mile, but it takes longer for the engine to spin up (remember this DOHC engine works better at higher rpm...remember where your peak power lies), you're losing mileage in the torque converter getting those tires spinning. It also takes more power than normal to cut through wind resistance at highway speeds. The only way you'll see higher mileage with a larger tire is if you start like a snail and then don't drive faster than about 45mph, only on flat ground, never in traffic.

Your "ideal" tire size with those gears is a 35 (that's gear ratio ideal, not real world ideal). Just keep all the above in mind if you make the jump. FWIW wasn't the stock low end mileage around 13mpg anyway?

-Sean
 

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Discussion Starter · #9 ·
a few answers...

i dont understand the question about mileage calculations corrected for tire size and gearing. assumy my speedo is correct, doesnt that give me an accurate miles/per tank of gas that i can calculate the mileage from?

Alum wheels. they are 16x8. new bridgestone revos, so a good all around tread ie not to agressive. i even run on the higher pressure side (36-38)

i have a full shell on the truck. it has been there since new.

no synthetics

brand new spark plugs... they are platinum 4's. i put those in around 50k and replaced at 90k.

the stock low end mileage was about 14. id get aroun d 17 on all freeway driving. also, when the truck was new, i was way nore agressive on the throttle... and still got low of 14.

i understand the larger diameter tires eating mileage. regearing should have helped that a bit. what im finding odd is guys with the same simialr setups are getting far better mileage. id love to be getting 13 on the low end. when i go on trips... what used to be 2 tanks is now 3 maybe 4.

i have noticed a bit in the past year or so, that every 10th time i start the truck i may get a little blast of white smoke.
 

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Is there a way to check for partially clogged catalytic converters? :confused:
 

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i dont understand the question about mileage calculations corrected for tire size and gearing. assumy my speedo is correct, doesnt that give me an accurate miles/per tank of gas that i can calculate the mileage from?

when i go on trips... what used to be 2 tanks is now 3 maybe 4.

i have noticed a bit in the past year or so, that every 10th time i start the truck i may get a little blast of white smoke.
I thought speedometer correction circuits only touched the speedo, not the odometer? Maybe that's not correct? Maybe it depends on the model...I don't know, so I won't speculate, but check with the manufacturer of your unit.

Try this...ignore what the odometer sez...pick a known distance, a long one, like a good 200 miles, driven (ie measured) in a vehicle with a known "correct" odometer. Start and end at the gas station...fill up and see if the actual distance/fuel is the same as what's on the odometer.

Dunno about the white smoke. I've tossed a can of Seafoam down the line in the past, dunno if that's helped or hurt me. Try the Engine/Drivetrain forum for that.

Something's wrong somewhere, it sounds like all of us are getting better mileage despite the mods. If you can narrow it down, I'll toss this thread to a forum for the specifics.

-Sean
 

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I just had a random thought...what about the fuel injectors? Could they just be wacked? I thought I read about another member that pulled his, and had them cleaned, balanced for flow, etc. I think a shop up in the Pacific Northwest did it?
 

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Re: bad mileage with all the mods

Hey buddy, with my setup (315's) and running 4.88's I get right about 13 mpg in my regular 17 mile (each way) commute. It's virtually all on surface streets. The best I've done on the freeway at a cruise control 70 mph was 14.9 mpg. I try to drive fairly easy on the throttle, but sometimes I just gotta go! :clown: Here's my tach readings for various speeds (with the Superlift speedo recalibrator and speed confirmed by hand-held Garmin GPS):

60 mph = 2,000 rpm
65 mph = 2,200 rpm
70 mph = 2,400 rpm

Towing our 26' travel trailer at 55 mph to 58 mph returns 9 mpg with OD turned off. Then I'm tacking about 2,600 - 2,800 rpm.

Just curious, are you running any synthetics? I'm running Mobile 1 in my engine and did a complete flush and fill last year with Amsoil for the tranny. I'm NOT running synthetic in the diff's because in the earlier model Tundra's, the axle seals were not designed for it. Some folks are running it without leaks, but I didn't want to take the chance.

Spark plugs? How do they look?
This is exactly what I get .. no synthetics

p.s. I'd get rid of the PLTNM 4's, but thats my opinion. Bosch (german plugs dont work well in a Japanese vehicle).
Stock NGK or Denso plugs work the best and Iridiums if it is S/C'd
Bosch plugs have to much internal resistance when they get hot and have a tendancy to melt coil packs and burn plug wires.
Toyota has a patent of the heat ranges of all their plugs, so unless its a factory number(plug) then all the other plug manufacturers are only close in their heat ranges.

Timing belt ok???

Have you tried disconnecting the battery for 30 minutes and then reconnecting? This will let the ECU re-learn driving habits.
 

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Re: bad mileage with all the mods

Now I don't know if its possible....bus I swear I got better mileage after a much needed tuneup. Like from 290 miles per tank to almost 350.
 

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As DevinSS mentioned larger tires and lower RPM often do not yield better mileage plus a larger tire will weigh more and require more power to get rolling and sustain a particular speed. Especially with a small V8 like the 4.7 that does not have gobs of torque on the low end. IMO the manufacture calculates the proper tire size to optimize the best fuel mileage for the size, weight, power and gear ratio of a particular vehicle. When you change that, fuel mileage suffers in my experience. I would really love to put a lift and big tires on my 05 Tundra 4x4 BUT it is a daily driver for me and with the gas prices being $1.00 per liter here, I'm spending enough on fuel already and I know doing this will only make it worse. As it is I changed my stock 265 70 series tires to LT 265 75 series and noticed a slight decrease in mileage.:sleep:
 

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Everyone also forgets that the fuel we get is what they give us.
We have no idea how 1 tank of fuel is vs the next tank. The amount of additives, are they the same? Did the driver put 87 in the 89 tank?
Have you ever seen a no name gas company pump fuel into the ground at a 76 station (I have). What kind of fuel was it? We will never know.
Did the station keep the tanks clean from excessive water or whatever contamination may have entered the tank?
Fuel quality has alot to do with it.
We really dont know what we are buying, only what they tell us it is supposed to be.
 

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Re: bad mileage with all the mods

Hey buddy, with my setup (315's) and running 4.88's I get right about 13 mpg in my regular 17 mile (each way) commute. It's virtually all on surface streets. The best I've done on the freeway at a cruise control 70 mph was 14.9 mpg. I try to drive fairly easy on the throttle, but sometimes I just gotta go! :clown: Here's my tach readings for various speeds (with the Superlift speedo recalibrator and speed confirmed by hand-held Garmin GPS):

60 mph = 2,000 rpm
65 mph = 2,200 rpm
70 mph = 2,400 rpm

Towing our 26' travel trailer at 55 mph to 58 mph returns 9 mpg with OD turned off. Then I'm tacking about 2,600 - 2,800 rpm.

Just curious, are you running any synthetics? I'm running Mobile 1 in my engine and did a complete flush and fill last year with Amsoil for the tranny. I'm NOT running synthetic in the diff's because in the earlier model Tundra's, the axle seals were not designed for it. Some folks are running it without leaks, but I didn't want to take the chance.

Spark plugs? How do they look?


I'm set up the same and this is what I am getting. Between a mix of street and highway, I see avg of 13.75 mpg.
 

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i think you have several things going on and your mileage problem is a result of them all working together.

i agree on ditching the 4 prong plugs. others have mentioned the same on the 4.7. stick with the toyota recommendations. take a 1 mpg hit for not following manufacturer's recommendations on a critical engine part. ;-)

as mustang points out, gas is a variable. some claim the winter gas has more oxygenators to burn cleaner during cold weather. oxygenators are less energy dense (like MTBE, ethanol, etc.) so energy per gallon is less. take a 1-2 mpg hit until weather warms up over 45 F in your area. (i refilled the truck last week, nothing else changed, mileage with the winter tires went from about 15 to almost 17. only thing obvious that changed was the temps were in the 60's and 70's the week before and spring was defintely in the air.)

bigger tires, more weight, more work to start and stop, more rolling resistance (they're wider, too, aren't they?) take a 1-2 mpg hit around town.

taller tires, taller truck, more wind resistance. lift kit? take a 1-2 mpg hit on the hiway.

i agree the gearing shouldn't matter much when matched with the proper tires. the jury is still out on the most efficient rpm cruising range on our trucks. it's probably somewhere between 2,000 and 3,000 rpms. it is a combination of factors that go into play and likely won't be the same for every body's truck. things that affect it would be stuff like: aftermarket exhaust, engine oil selection, intake mods, etc. power extracted, etc.

an engine runs most efficiently when the friction generated by the pistons moving up and down is balancecd by the max torque out put and the throttle butterfly is at least 70% open. of course, if you don't use all the power available in this condition to move forward, you won't be getting the max efficiency from the engine. that is why it's important to choose the correctly sized engine for the job you want to do. problem is, most of us want the engine to do lots of different jobs (4 wheeling, towing, cruising, hauling, etc.) so it's always a compromise.

the white smoke is a known issue on the 4.7 during startup after the engine was start and run for a short time. for example, if you back the truck out of the garage and then shut it off right away, there is still gas in the intake and cylinders. the next time you start it up, there will be a puff of white smoke.

i think you can see some significant improvement if you change a few things. also, i would check to see if any of the wheels are warm after driving to find out if a brake is dragging. and, verify your calculations as posted above by driving a known distance or using mile markers on the interstate. 9 mpg seems a bit low, but with your mods, i wouldn't hope for much more than 13 or so.

good luck!

(if nothing else helps, you might want to try an alignment. with bigger tires, even a slight misalignment would give you a decent mpg hit.)

(oh, and what about egr valve? when was it replaced? sometimes they won't throw a cel.)
 
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