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Hey all. I had a 2002 Limited Access Cab V8 with 109k miles before the wreck. The Insurance company totaled it out and paid me back very well, to the tune of $14k before my deductable. I found a clean 2004 SR5 Double Cab V8 with 140k on it. I have replaced the timing and drive belts, fuel filter, spark plugs and one O2 sensor. Put part of a can of Seefoam through the top end and dumped the rest in the tank.

My question and issue is this: I could get near 20 MPG in the 2002 if I stayed at or below 2000 RPM / 65 MPH. Now in the 2004 I can't touch anything over 17 MPG. I can't force myself to drive any slower than 60 on the highway, but at that point I am still at 2250 RPM.

Anyone know if there is a signifiant amount of weight increase in the DC that would effect RPM's at cruising speeds, or of another reason 65 MPH in the DC is not close to the 2000 RPM it was the AC? It's a sweet truck and my kids love the room and the independant doors in the DC vs. the AC. Just hoping to better my MPH without too much self-imposed governor on speed. Thanks for anyone's info on this one. (Go Rockies)
 

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It's likely partly the gearing.

IIRC a Tow package equipped DC has 4.10gears

by the numbers I'd fathom a guess your old Tundra had 3.73's or similar

another thing to consider is a DC is a heavier truck that is bigger than an AC in every way (not just length). However this said my Tundra will get in the 19's on the HWY and average over 17 overall in all driving (1300 mile average). Lastly when you get right down to it some individual trucks will just do better than others that may have rolled off the assembly line that day.

size of an AC compared to a DC
http://www.tacomaterritory.com/forum/showthread.php?t=153385
 

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It's likely partly the gearing.

IIRC a Tow package equipped DC has 4.10gears

by the numbers I'd fathom a guess your old Tundra had 3.73's or similar

another thing to consider is a DC is a heavier truck that is bigger than an AC in every way (not just length). However this said my Tundra will get in the 19's on the HWY and average over 17 overall in all driving (1300 mile average). Lastly when you get right down to it some individual trucks will just do better than others that may have rolled off the assembly line that day.

size of an AC compared to a DC
Hey Krochus,

Great observations on the gearing which leads to two other very critical considerations.

  1. The 2004 has a four speed automatic transmission whereas you have a 5 speed transmission.
  2. The 2005 and 2006 have VVTi whereas the 2004 does not.
Most people agree that keeping the RPM's below 2,000 is a great way to conserve fuel but with a 2004 running at 75 MPH on the highway I ran at 2600 RPM - this was just keeping up with traffic. After I swapped out my gears I could run at 2200 RPM and 75 MPH.

Another consideration is that the 2004 is only rated at 242 Hp. the 2005 and 2006 were rated at 271 and 285 Hp. All these things have an effect on MPG.


Hey all. I had a 2002 Limited Access Cab V8 with 109k miles before the wreck. The Insurance company totaled it out and paid me back very well, to the tune of $14k before my deductable. I found a clean 2004 SR5 Double Cab V8 with 140k on it. I have replaced the timing and drive belts, fuel filter, spark plugs and one O2 sensor. Put part of a can of Seefoam through the top end and dumped the rest in the tank.

My question and issue is this: I could get near 20 MPG in the 2002 if I stayed at or below 2000 RPM / 65 MPH. Now in the 2004 I can't touch anything over 17 MPG. I can't force myself to drive any slower than 60 on the highway, but at that point I am still at 2250 RPM.

Anyone know if there is a signifiant amount of weight increase in the DC that would effect RPM's at cruising speeds, or of another reason 65 MPH in the DC is not close to the 2000 RPM it was the AC? It's a sweet truck and my kids love the room and the independant doors in the DC vs. the AC. Just hoping to better my MPH without too much self-imposed governor on speed. Thanks for anyone's info on this one. (Go Rockies)
Hey 303Tundra,

Congratulations on the 2004 DC - great truck!! Mileage is going to be a challenge for you. I have done extensive modifications to mine to get better fuel economy:

  • Ram air intake scoop with direct connect to the air box
  • Relief holes in air box to vent some of the excess vent air out and also blow out the dirt and debris that makes its way into the air box. I am currently testing one of my theories that by providing a constantly refreshed charge of incoming air that the intake air temperatures will be lower.
  • Getting ready to do the Throttle Body coolant bypass this afternoon.
  • True Flow intake with True Flow wet foam filter
  • Aero Turbine muffler with foolies
  • Fitch Fuel Catalyst Tundra Fuel Economy: Fitch Fuel Catalyst Findings
  • Nitrogen in tires and running at the highest pressure possible.
  • Re-geared from 4:10's down to 3.91 gears in front and rear differentials. (not exactly by choice)
There are a ton of factors that will influence fuel economy:

  • Driving style
  • clean oil
  • clean air filter
  • proper tire pressure
  • no brakes dragging
  • good fluids in transmission, transfer case, and differentials
  • lubed drive line
  • proper alignment
  • smooth acceleration
  • clean injectors
  • good plugs (Denso or NGK - NOT Bosch!!!)
  • Quality of gas - the longer gas has sat somewhere (either at the break-out delivery farm or rack or even in the underground tanks at a gas station the more it degrades) Tundra Fuel Economy: Gasoline
  • Tire size/rolling resistance

There are a few more things I want to do to my truck:

  • Adjusting the angle of the tailgate - I have already done this and think I have found the optimum angle but I need to test this over a long period of time in order to be able to gather enough data to formulate any solid conclusions
  • aerodynamic skid plate and underbelly pans
  • electric fans
  • headers
  • and an invention I developed over the past 6 years that worked on my Tacoma but I am still fooling around with on my Tundra.
At any rate, good luck to you and let me know if you stumble upon anything new that works for you.
 

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Most people agree that keeping the RPM's below 2,000 is a great way to conserve fuel
I do not, because the real answer is "It depends"

IME especially coming from a Jeep and hotrodding background where such observations are common. Folks mistakenly assume that higher the final drive and therefore lower the RPM the higher economy will be. This is actually false. In cases where the hearing is TOO high MPG can begin to suffer

Most engines have an rpm range where they make the best economy because they're operating under the least load. In my experience shorter stroke engines in the 4 to 5 litre range return best numbers when the cruise RPM is right around 2k + or - a couple hundred rpm. Drop the revs much below that and you begin to lug the engine and have to operate at greater throttle openings to maintain speed.

More on piston speed vs MPG
The Internal-combustion Engine in ... - Google Books

at the bottom of the page
http://go.jeep-xj.info/HowtoSpeedoGears.htm
 

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I do but with a caveat

IME especially coming from a Jeep and hotrodding background where such observations are common. Folks mistakenly assume that higher the final drive and therefore lower the RPM the higher economy will be. This is actually false. In cases where the hearing is TOO high MPG can begin to suffer

Most engines have an rpm range where they make the best economy because they're operating under the least load. In my experience shorter stroke engines in the 4 to 5 litre range return best numbers when the cruise RPM is right around 2k + or - a couple hundred rpm. Drop the revs much below that and you begin to lug the engine and have to operate at greater throttle openings to maintain speed.

More on piston speed vs MPG
The Internal-combustion Engine in ... - Google Books

at the bottom of the page
http://go.jeep-xj.info/HowtoSpeedoGears.htm

Very true and I agree. There is an optimum RPM at which the air resistance of the vehicle and engine speed are ideally suited to each other. I have found that my optimum seems to be right around 75 MPH.
 

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My 06 dc has never broken past the 18mpg barrier.
 

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EPA says 13 MPG city & 16 MPG Highway? on a 2004 V8 no matter if it's a 4x4 or 4x2?
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18 MPG on an 06 DC is great mileage!!

Many Factors Affect MPG

When I bought my truck I was getting around 14-15 MG on the highway and drove it like a little old lady. I shut it off at long stop lights, accelerated slowly, and coasted for miles.

Now I run the p!ss out of it, horse around by gunning it, and do not think twice about blowing somebody's doors off when they drive too slow or wander in their lane. My best mileage to date is 19.96 MPG but have not entered that particular receipt into Fuelly yet. I just got settled in to my new living quarters and am still unpacking boxes, getting taxes finished, suing the idiot who stole my business, studying for another insurance license, landscaping my girlfriend's property, raising my son - but generally just being lazy. I do intend to get all of my fuel receipts entered as soon as I get all my paperwork done and I am interested to see where I end up.
 
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