Okay, still have a few more tricks up my sleeve but this is just the beginning. Take into consideration that at 75 MPH I am actually doing 78 MPH. I will be installing the true speed when I get the time - hopefully this weekend. I also have the passenger side manifold O2 sensor out to lunch and need to replace that this weekend too.

At any rate, 78 MPH divided by 75 MPH yields 1.04. I ran until the tank was dead nuts half way and looked at the odometer and she read 233.7. So:


233.7 x 1.04 = 243.048.
243/12 = 20.254.

Let's just call it 20 MPG. Two pictures below. First picture shows the speed at which I ran and the tank just a hair over half full. Second picture shows the RPM's along with the cruise control set and the CEL for the failed O2 sensor. I would have snapped a picture of the tank at dead nuts half full but by that time I was navigating the turns onto 465 and through traffic.

All this in a four speed automatic, four wheel drive, Double Cab. The new ram air intake scoop is finished and the mounting bracket will be fabricated this week as well. I expect the performance numbers to improve slightly but nothing major beyond what I currently have. The next two modifications (Headers/y-pipe and electric fans) should place me squarely at 22 MPG. The last modification will be another of my own design and I hope to push into 25 MPG on the highway.

That is pretty amazing. Was the truck completely empty? I just got a Scangauge II and could get better mileage if I lived on flat land. I was recently driving on a level road and was getting 22 - 24 mpg by keeping my foot light. The starts and uphills are where I lose everything. I live in the mountains and constantly haul 800 lbs. plus.

What headers and fans are you looking at. I was contemplating doing the electric fan conversion myself. Also read about changing out the... brain fade... underdrive pulley?

i've had mine go over 200 miles at half tank twice.

Seem like the little green shifter light has gone out on your truck !

so is 75 the speed you see the best MPG? it seems that most people on here get the best at 58-65

I am looking forward to your electric fan conversion. Which one are you leaning toward? I want to do this mod as well and am looking at the Flexalite 775 made for our Tundras.

if im driving on the freeway only
long trips 60-65 mph
my truck will get 250-260 on half tank
the best ive gotten so far is 22mpg
driving from stockton down to san diego

That is pretty amazing. Was the truck completely empty? I just got a Scangauge II and could get better mileage if I lived on flat land. I was recently driving on a level road and was getting 22 - 24 mpg by keeping my foot light. The starts and uphills are where I lose everything. I live in the mountains and constantly haul 800 lbs. plus.

What headers and fans are you looking at. I was contemplating doing the electric fan conversion myself. Also read about changing out the... brain fade... underdrive pulley?

Hey Rob,

Thanks for the kudos - it has been an interesting trial and error process for me; sometimes at rather embarrassing expense. On the trip down to the river we had 100 pounds of electrical cable to try and repair a drop that accidentally got cut by a zero turn mower. Probably not a good thing for people to drink and then mow the grass but I digress. We stopped three times on the way down for bathroom breaks and got lost on the river and ended up tooling around Madison and then Veevay until we found our road. It was the first run to the river for me. Just me and my son in the truck as far as passengers.

The first part of the trip was mostly flat but down at the river it was pretty hilly until we got to our location. No major hills but certainly nowhere close to flat either. Both directions out and back were in constant, sometimes heavy, rains.

Unfortunately Boost Brothers do not produce a header for my year truck - if they did then that is what I would shoot for. As it stands I will probably go with JBA which is a sizable chunk of change and will have to wait until I get some other bills taken care of first. I am still trying to get the money together to pay for my front differential.

I am looking at the perma cool electric fans as well as the Flexalite but have not made any decisions in that area yet. I still have some time to research that modification before the end of he summer.

I would love to get a Scanguage but there are always pressing bills to be paid and I am bucking hard to get the truck paid off this year so I can go to college. Maybe I could convince Boost Brothers to make a set of 2004 Tundra headers and have them donate them to me for testing. I could post up all the results on my Blog (http://tundra-mpg.blogspot.com/). Sponsorship would be a very good thing. - maybe one day. Then again, monkeys may fly out of my @$$ holding $100 bills shouting hallelujah.

22- 24 MPG with DC is phenomenal!! Now I feel totally inadequate.

i've had mine go over 200 miles at half tank twice.

Time permitting I would be happy to try and help you work on that. With an Access Cab I think that there is more potential for improving fuel economy than there is with a DC. In the meantime you could start by adding a Throttle Body spacer from the website you link to.:nono:

22- 24 MPG with DC is phenomenal!! Now I feel totally inadequate.


Hey Highway,

Don't... it lasted all of about 5 minutes and I probably had a tailwind. :laughing:

My best average by tank mileage for the DC so far was a little over 16 and I usually don't get that. Too much stop and go, short trips, hills, and not paying enough attention to the foot. That was one reason I got that scangauge. To see how and when I can really make the difference. For me it seemed like the most inexpensive attempt at fuel economy... but then I do own a truck. :) I know I can't expect much since it is my work truck/daily driver. I have contemplated an economy car purchase but then I have the whole two vehicles to insure yada, yada, so it would not really pan out unless I got a super sweet deal on something fun and economical.

I never got very good mileage in my 03 AC and I had that one for 5 years. I think the best I got in that truck was about the same... 16... going down hill ;) ... so it sounds like you are doing some good stuff.

Good times with your son... spend as much time as possible there (I am sure you know that already). I went through divorce just a couple of years ago and still kind of getting over it. My daughter is 5 and I spend as much time as possible with her. I know that soon it will be her telling me to give her some space but until that time I am taking all opportunities to be with her. Her mom limited my time to two days per week (and it is not worth fighting for more because you know how ugly it can get) but there is a lot of extra time I swing in. Hope things are going well on that front!

Also curious, what happens if that electric fan goes out... SOL? That is what has me hesitant on that mod but I have read people feel like they have had good results. That plus the underdrive pulley, plus headers, plus exhaust. Lots of money, maybe just spending it on gas is fine.... NAH :crazy: Now what fun would that be??

Seem like the little green shifter light has gone out on your truck !

Yeah, it is a little annoying but time right now is pretty limited for me so it will just have to wait. I just pretend my truck is "personalized."


so is 75 the speed you see the best MPG? it seems that most people on here get the best at 58-65

I think at a lower speed the MPG's would be even better but around here if you do not run 75 MPH on the highway you will get run over. Besides, my research, development and testing is meaningless to most people if I cannot demonstrate that I can at least keep up with the majority of traffic.


I am looking forward to your electric fan conversion. Which one are you leaning toward? I want to do this mod as well and am looking at the Flexalite 775 made for our Tundras.

I have not made a decision yet. I am going to try and get the truck paid off first, get some bills paid down, make it through the summer, and do a bunch more research. I am seriously considering asking perma cool or flexalite to sponsor my testing by providing a unit to install on my truck. It is definitely something I want to do.

if im driving on the freeway only
long trips 60-65 mph
my truck will get 250-260 on half tank
the best ive gotten so far is 22mpg
driving from stockton down to san diego


Wow, those are some really nice numbers. That five speed transmission and variable valve timing really make a difference. I may make a run at 60 MPH to see how the numbers return but I am worried about getting run over. People around here like to run out hard on the highway. Not that I am complaining as I like to run the truck out with the rest of them. I know that the faster you run the more power (fuel) it takes to do so.

Hey Highway,

Don't... it lasted all of about 5 minutes and I probably had a tailwind. :laughing:

My best average by tank mileage for the DC so far was a little over 16 and I usually don't get that. Too much stop and go, short trips, hills, and not paying enough attention to the foot. That was one reason I got that scangauge. To see how and when I can really make the difference. For me it seemed like the most inexpensive attempt at fuel economy... but then I do own a truck. :) I know I can't expect much since it is my work truck/daily driver. I have contemplated an economy car purchase but then I have the whole two vehicles to insure yada, yada, so it would not really pan out unless I got a super sweet deal on something fun and economical.

I never got very good mileage in my 03 AC and I had that one for 5 years. I think the best I got in that truck was about the same... 16... going down hill ;) ... so it sounds like you are doing some good stuff.

Good times with your son... spend as much time as possible there (I am sure you know that already). I went through divorce just a couple of years ago and still kind of getting over it. My daughter is 5 and I spend as much time as possible with her. I know that soon it will be her telling me to give her some space but until that time I am taking all opportunities to be with her. Her mom limited my time to two days per week (and it is not worth fighting for more because you know how ugly it can get) but there is a lot of extra time I swing in. Hope things are going well on that front!

Also curious, what happens if that electric fan goes out... SOL? That is what has me hesitant on that mod but I have read people feel like they have had good results. That plus the underdrive pulley, plus headers, plus exhaust. Lots of money, maybe just spending it on gas is fine.... NAH :crazy: Now what fun would that be??

Hey Rob,

Thanks for the advice/encouragement with my current situation and the importance of being here for my son. I know it is a tough time for everyone but he deserves better.

As far as the electric fans from what I understand they are pretty reliable nowadays. The weak link is the controller and they have improved vastly over the past couple of years. Many manufacturers (primarily those who made the transverse engine vehicles) have utilized the electric fans for years (some for decades) without complications. I think I read somewhere that you can set the thermostat for summer or towing and then re-set it for winter driving. It would be nice to have that type of fine tuning ability.

I think I may test out the Throttle Body coolant bypass for the summer to see what happens. Worth a try.

I drove from Indy to Tell City this past weekend. Drove 377 on 19.2 gallons. I have an 01 4x4 AC. This is probably the best I have done. I typically average 16.9 mpg on a mix of city and interstate. This weekend I changed the oil about 2 hrs before we left and I also filled up with premium.

I've been close to pegging 20mpg the last couple weeks on my normal commute. I typically get 18ish on my way to work (17 on the way home) but a couple weeks ago filled up at Sheetz and my mileage (and power) instantly jumped for the two tanks I ran. Had to fill at a Marathon last friday on the way home and this morning I was back to 18mpg. This is all according the the current calc. on the scanguage. My return trip is almost always 1mpg less regardless. Sheetz station is out of my way but I will try to buy there again and see if it jumps again. I've never seen much of a difference between brands...I bounce between Shell, Fuel-mart, BP, and Marathon regularly.

wouldn't you get a better/real MPG if you ran the tank almost completely empty? i've noticed that you get further on the first half tank than you do on the second half tank. or is it just me?

I drove from Indy to Tell City this past weekend. Drove 377 on 19.2 gallons. I have an 01 4x4 AC. This is probably the best I have done. I typically average 16.9 mpg on a mix of city and interstate. This weekend I changed the oil about 2 hrs before we left and I also filled up with premium.

Darn good numbers there with that Access Cab. Nice little day camp down there in Tell City.



I've been close to pegging 20mpg the last couple weeks on my normal commute. I typically get 18ish on my way to work (17 on the way home) but a couple weeks ago filled up at Sheetz and my mileage (and power) instantly jumped for the two tanks I ran. Had to fill at a Marathon last friday on the way home and this morning I was back to 18mpg. This is all according the the current calc. on the scanguage. My return trip is almost always 1mpg less regardless. Sheetz station is out of my way but I will try to buy there again and see if it jumps again. I've never seen much of a difference between brands...I bounce between Shell, Fuel-mart, BP, and Marathon regularly.

I wish I had a five speed rather than the four speed. I have recently noticed that even though all I run is Shell87 that my mileage can vary from one station to the next. I have not decided if this is because at some stations the gas sits longer in the tanks or if some stations (one in particular out by the airport) are trucking in cheaper gas at night. The rumor is that this particular station is buying off-brand gas that has been sitting for a few months. I have also noticed improved performance as well as mileage when going from one brand to another but I have not pinned down the correlation. Even if there were a correlation I think at some time one would reach a point where you would have to start over with the chain of events. Perhaps combing certain brands of gas (ie their additives in particular) would yield an improvement? Tons of theories to test.


wouldn't you get a better/real MPG if you ran the tank almost completely empty? i've noticed that you get further on the first half tank than you do on the second half tank. or is it just me?

As long as fuel economy is calculated by dividing the driven miles by the gallons pumped the numbers should always be accurate. However, having said that, I always try to run out at least a half of a tank of fuel before refueling. As I have referenced before in other threads I have kept very accurate track of my fuel economy since the day I drove it off the lot. I have a pretty good handle on where I am at with the numbers even by just looking at my fuel gauge. Unfortunately I was unable to refuel after I got back to Indianapolis (I have $10.52 to my name) and had to do in town driving the next day while installing a drain line on a property. I really would have liked to top the tank off and find out where I was at with some degree of certainty. I will be making another river run in two weeks and will log the numbers from that as well.

To address your observation I have noticed that a few times too. Sometimes it seems like the top half of the tank does better than the bottom half from just eyeballing it. Fortunately or unfortunately as my fuel economy improves I have to drive longer highway distances to test this observation. To be certain, the more miles run the smoother the overall curve becomes when logging fuel economy.

just got back from the weekend and got 171.3 to the half tank. with camping gear and kids @ 75mph. whats that, about 15mpg? just wanna throw mine in there. :p

Sometimes it seems like the top half of the tank does better than the bottom half from just eyeballing it.

Two reasons for this.

1. The gauges are calibrated so that "empty" is not empty so you have some reserve.

2. You can actually burn the first half of the tank completely without running out of gas!


So in my case I'm usually around 200 miles at the halfway point....roughly 16.5mpg on 12 gallons. Reserve has 3-4 gallons...so the 2nd "half" on the guage is only good for about 8-9 gallons or 130-150 miles for a total of 330-350 miles between fill-ups which is about right for me.

. . . . Reserve has 3-4 gallons...so the 2nd "half" on the guage is only good for about 8-9 gallons or 130-150 miles for a total of 330-350 miles between fill-ups which is about right for me.

I respectfully disagree. The second half of the tank is 12 gallons. Total tank capacity is 26.4 gallons. Top 12 plus bottom 12 equals 24 gallons with 2.4 gallons reserve. My fuel light comes on at 22 gallons which is before the needle hits the bottom mark on the fuel gauge.

The only way to know for sure is to actually fill your tank. Gas gauges are not accurate enough to make precise guesses about fuel consumption.

It has been awhile since I posted in this thread so I thought I would update progress. A few more modifications since the last time I was in this thread:


Installed the new scoop with a curved floor and a narrower convergence at the back which has vastly improved the air flow. http://www.tundrasolutions.com/forums/forced-induction-systems/173400-ram-air-intake-scoop/
Routed out the ribs on the upper half of the air box http://www.tundrasolutions.com/forums/1666294-post7/

Currently I am getting some very nice numbers in the mileage department. 65 MPH on the highway gets me 21-22 MPG. Running from my house to my sister's house (basically all flat) I get 23 MPG at 65 MPH which includes several miles of non-highway running. Total trip distance is just a little over 22 miles.

I am in the middle of testing the Fuel Doctor for Jason over at Tundra Headquarters and while this device may have affected my fuel economy I do not believe it is solely responsible for my improvement. I have another 4,000 miles of testing to do but the Fuel Doctor testing is suspended until the end of the month to allow the fuel type here stabilize with the changeover from winter blend to summer blend. In the meantime I decided to design and test my diffuser.

I understand that some people have a problem with my results and I think it helps to take into account that my modifications work in conjunction with each other. Simply doing one of them without the others may not return the kind of gains I have netted so far. On the one hand I had planned on enjoying 20 MPG for awhile and having overshot that number I feel like I am missing out. I guess I will have to learn to live with the current numbers. The real test will be the tank average rather than just the trip average on the highway.

I have not done the electric fan conversion or the headers but they are still on the list. Still working at getting bills paid down.

The only way to know for sure is to actually fill your tank. Gas gauges are not accurate enough to make precise guesses about fuel consumption.


I agree. However, the comment was in reference to the tank capacity. Even so, here is how I figure my fuel my fuel economy:

http://www.tundrasolutions.com/forums/fuel-economy/202919-how-to-calculate-miles-per-gallon/

Back down to 21 MPG at 70 MPH with no Ram Air Intake Scoop. Will fabricate new scoop for bumper location after a few more paychecks and reinstall.