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What RPM do you tow at for optimal gas mileage

Discussion in '2nd Gen. Tacomas (2005-2015)' started by dougmays, Sep 8, 2009.

  1. Sep 8, 2009 at 12:49 PM
    #1
    dougmays

    dougmays [OP] Well-Known Member

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    When your towing a "heavy" load (4000-6500lbs) what is your target rpm for optimal gas mileage? I recently towed a 1964 studebaker on a uhual flat bed (around 5500lbs) and i was tryin gto keep it right above 2500rpms to keep the speed between 75-80mpg. i think i averaged 13 mpg.

    just wondering what everyone else does? do you sacrafice speed and time for lower rpm's and save on gas. or does having a tow package not really matter and you drive at normal speeds?
     
  2. Sep 8, 2009 at 12:56 PM
    #2
    wiscdave

    wiscdave Lets Do It!

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    I tow 65-70 mpg in 4th for the best mpg.

    Put it this way, do you have more time or money to buy gas? For me, I have the extra time.
     
  3. Sep 8, 2009 at 12:59 PM
    #3
    taco06

    taco06 Well-Known Member

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  4. Sep 8, 2009 at 1:12 PM
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    Demoncleaner

    Demoncleaner Well-Known Member

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    Jesus, slow down man. I wouldnt tow anything 75-80, let alone a 5500 lb load behind a 4200 lb truck. Anything abrupt happens, other drivers, blowout, whatever it ain't gonna be pretty. end safety rant.

    Heavy weight like that at more reasonable speed, yea I'd keep it over 2500.

    Lighter loads like 1500-2000lbs I keep it 100-200 rpms higher than normal. Only lose 2-3 mpg.
     
  5. Sep 8, 2009 at 1:18 PM
    #5
    dougmays

    dougmays [OP] Well-Known Member

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    when you say slow it down but keep it above 2500rpms....thats the part i'm kind of questioning. because i was towing a heavy load but at 2500 rms i was going minimum of 70. I also noticed that i was reaving really high in 4th so i shifted up to 5th and that seemed to put less strain on the engine. i was on I-10 in the florida panhandle so no hills. are our trucks just beasts like that or do i want to downshift to 4th and keep it below 70?

    thanks
     
  6. Sep 8, 2009 at 2:17 PM
    #6
    jgguns

    jgguns Member

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    The Tacoma is a nice capable truck but it is by no means a "Towing Beast". It is not set up to be a heavy hauler nor does it have the brakes to be a heavy stopper. I know it is rated for 6500lbs with the tow package but I would take it very easy with anything above the 4K mark. It was not designed to tow that kind of weight at speed...Check out to rear leaf pack.
     
  7. Sep 8, 2009 at 4:25 PM
    #7
    j4x4ar3

    j4x4ar3 Well-Known Member

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    Towing speed limit here is 55 so I keep it under 60. That's the best way to get good gas mileage. Even then don't expect much more than 10-12 with a heavy load. RPM should only be used to make sure you're not bogging the engine down. It will vary from tow to tow and the wind/terrain.
     
  8. Sep 8, 2009 at 4:31 PM
    #8
    XrunnIT

    XrunnIT Well-Known Member

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    when towing real heavy loads, your best performance will come when you are closer to the peak VE (volumetric efficiency).

    Depending on what mods you have, the peak VE will vary. Peak VE happens at the same time as peak torque. Know your peak torque, and you'll know the most optimal RPM to use. :thumbsup:
     
  9. Sep 8, 2009 at 4:58 PM
    #9
    Isthatahemi

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    No offense intended, but that is wrong. 4000 RPM (peak torque rpm)is not ideal for mileage....
    Peak Efficiency comes at the lowest RPM that you can maintain the desired speed. My experience with a scangauge is as long as you are above 1500 RPM, the best mileage will be attained by running the highest possible gear, regardless of throttle position. One your truck a steady thottle foot, keeping the load high, and just shy of the tranny kicking down. As for Volumetric efficiency, large throttle openings are key, not peak torque RPM, as it relates to mileage.
    For example, 85% throttle in 5th, will net better mileage than 70% in fourth for 2 reasons, the injectors are cycling far less frequently(ie; once every 2 engine rotations), friction and pumping losses are lower. I bought a scangauge for this exact reason....To find out what you are asking...
     
  10. Sep 8, 2009 at 5:42 PM
    #10
    dougmays

    dougmays [OP] Well-Known Member

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    So isthatahemi...what speed/rpm do you usually run at when towing a heavier load. i wanna get a scangauge for this but cant afford right now
     
  11. Sep 8, 2009 at 6:17 PM
    #11
    Isthatahemi

    Isthatahemi Well-Known Member

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    BFG AT's, Weathertechs, Hoppy's brake controller.
    I have a 4cyl. However they have similar torque characteristics, RPM,Curve etc.
    I tow at 70 mph (75 indicated), My truck runs around 2650ish rpm, or around 3100ish in 4th. 4th feels better, more effortless, less vibration. But the scangauge says 5th is better for mileage. Runs approximatly 90% load, 4th is around 70% load.
     
  12. Sep 8, 2009 at 6:28 PM
    #12
    XrunnIT

    XrunnIT Well-Known Member

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    No offense is ever taken.. but I never said anything about best mileage. I purely stated best performance. My peak torque is at 2500rpms

    What may be best for best MPG, may not be best for the motor (as it pertains to hauling weight and having a high cruising load). If the motor is running more efficiently, it is going to run better.

    More throttle = more air = more gas
    Higher RPMs = more cycles = more gas

    I would like to see some numbers and raw data supporting your theory. Meaning inj duty cycle, rpms, load, MAF included. With those we can calc how much fuel is being used per cycle. The load feature on the SGII isn't accurate, so i don't trust the real MPG too much when load is higher then normal cruising (about 25% for the 4.0L)

    While you claim better mileage with 85% TPS in 5th over 70%tps in 4th, if hauling a heavy load where you are needing that much throttle just to maintain speed, then its time you look into more performance. A stronger truck or more power.

    There is a correct gear for everything. The more load your creating the more proper gear selection is key to protecting the engine. If you need 85% in 5th gear to keep the vehicle moving at a steady state, then you are overworking the motor. At 80% throttle the ECU sees it at WOT. If you are WOT at 2500rpms just to maintain speed, you are asking for problems, and opening yourself up for knock and potentially risking disaster.
     
  13. Sep 8, 2009 at 6:38 PM
    #13
    RelentlessFab

    RelentlessFab Tacoma offroad armor fabricating beast Vendor

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    Had tons on the old Taco's.... new Tundra is pretty stock
    I tow A LOT and there are a lot of variables to this question. Some that come to mind:
    -Terrain. Are there hills, or are you constantly on flat ground
    -Weather. Is there wind? Head wind or tail wind will affect the load on the truck.
    -Trailer style/load. If you have a trailer with a lot of frontal area(enclosed trailer, travel trailer, etc) then the wind drag will a large affect compared to say a flatbed with a pallet of bricks on it which will grab little air.
    -Truck setup. Are there any performance mods on the truck? A lift and over sized tires? etc.

    With my 6 speed, I just listen to the truck and feel the load on it to determine my gear choice. With a load as described I would run 5th on flat, 4th on any little grade and 3rd on steeper grades to maintain speed and VERY rarely hit 6th as it is like overdrive on the Auto. I wouldnt tow anything at speeds faster than 65mph, even on an open interstate. I typically go between 55-60 when towing and my trailer is set up with brakes on both axles so I can stop my loads.
     
  14. Sep 8, 2009 at 6:45 PM
    #14
    dougmays

    dougmays [OP] Well-Known Member

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    thanks for the explanations relentlesstaco! i do think i'm gonna start sticking to the 65 mpg range. i live in florida so i'm mostly driving on flat. i was just suprised that towing to new orleans from florida i was in 4th and it was reving to about 3000rpms so i shifted to 5th and the rpm's went down and a smoother ride. i just figured i'd need to stick in 4th for that kind of load.

    are there any negative affects of towing with lower rpms? ideally you want the rpms as low as possible correct? unless going up hill? or could lower rpms actually out more stress on a engine?
     
  15. Sep 8, 2009 at 6:53 PM
    #15
    XrunnIT

    XrunnIT Well-Known Member

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    lower rpms are generally best for mileage. But when you start stressing your motor there is more important things to address.

    Trying to save 1-3mpg isn't worth risking knock, damaging the ring lands, etc.

    This goes back to putting your rpm in your power band.

    Safety > small loss in mileage
     
  16. Sep 9, 2009 at 7:10 AM
    #16
    dougmays

    dougmays [OP] Well-Known Member

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    power band?
     
  17. Sep 9, 2009 at 2:56 PM
    #17
    Isthatahemi

    Isthatahemi Well-Known Member

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    BFG AT's, Weathertechs, Hoppy's brake controller.
    There is nothing to suggest a modern Toyota engine with knock sensing, electronically adjusted timing, and rock solid bottom ends, will be harmed by lugging it. Besides, and auto will downshift if you lug it. My research suggests that run the highest gear you can without it downshifting. All the scary talk of doing damage is not a reality on your particular vehicle.
     
  18. Sep 9, 2009 at 4:11 PM
    #18
    XrunnIT

    XrunnIT Well-Known Member

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    Knock sensing is great, but when its sensed, its because it already knocked.

    Electronically adjusted timing... the factory ECU has a set map that it reads from, and is only dynamic based on then input sensors (MAF, WRAF on closed loop only, etc). It will pull timing, but it pulls timing after its already knocked. While the bottom end is rock solid, that's not where the problem is. The 1GR motor has very weak ring lands, that damage/break easily when exposed to knock.

    Most of my focus on these trucks is performance based, and high load environments. They knock just as easy as any other motor if not more because of the high compression (10:1).

    Lugging the truck is bad for the motor, simple as that. Whether or not it knocks everytime is irrelevant, your putting way more stress then needed, and not a good idea.
     
  19. Sep 9, 2009 at 6:51 PM
    #19
    Isthatahemi

    Isthatahemi Well-Known Member

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    BFG AT's, Weathertechs, Hoppy's brake controller.
    How do you lug an engine with an electronically controlled transmission? You don't, so it's not a factor in this discussion.
    There is nothing weak about the 1GR, unless you get into modding, especially Forced Induction......
     
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