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Tow Haul Mode better gas mileage?

gixxerboy

Full Member
Joined
May 18, 2006
Messages
71
Has anyone noticed that driving 60 and under in the city in tow haul mode the engine seems to stay in 4 cylinder more or is it just me?Driving on the highway it seems to have no effect? :D Just trying to save gas!
 
I don't see anyway using the tow-haul mode can result in anything other than lower gas milage. Pushing that button does a number of things including, but not limited to, making the fuel mixture richer and adjusting the shift points higher. The last time I used it was hauling a F@#D on a trailer approximately 500 mi. Gas milage was about 5 mpg lower than normal.
 
Gixxerboy Funny you mention that.

I had a small trailer with trash on it last night and I doubt it was over 300 lbs.  I looked at the tow button and laughed because I really did not feel the trailer.  But on the way home decided to toy with it and when I did I noticed the RPM go higher but the V4 came on and the MPG went higher.  I thought at first I was nutz then I started testing it and it happened every time. I t would go to V4 with higher revs (just a tad) then drop to V4 until I hit the gas and made it go to V8.  Everytime the V4 was on the mpg was in the 20s compared to mid teens in V8.

I thought it was a fluke but now that I see I am not the only one out there seeing things I am going to test it with a tank of gas and see if it is for real or just a computer error on the display.

 
That seems reasonable.  Lower overall gear ratios using tow haul would allow less strain on the motor so the V4 might be available in more situations.  If this is so, perhaps the 4.10 will do better around town than the 3.73 if you keep a light touch on the pedal or use cruise control even at lower speeds.

 
I've actually noticed driving uphill in some cases gave me better gas mileage while maintaining the same speed then without. More power for the same gas burnt.. Kinda like the obvious way to go but the auto trans usually like to hang inthe high gears. The tow button jumps down quick.
 
I also noticed this several weeks ago.  I drive about 75-100 miles a day, in city and on the city freeways.  The tow mode really does increase the mpg as long as you are going below 60.  I have found the best milage when on cruise control.
 
This makes sense to me more and more.  I have the 4.10s, and even on the highway I'd be willing to bet that it runs in V4 mode more than a 3.73 would under my driving conditions and style.  Mainly because our engines all make more horsepower at higher rpms (peak hp is at 5200 rpms), so that should be true for the V4 mode as well as the V8 mode.  To me this means that my lower gearing in the rear, which normally causes a V8 only vehicle to burn more fuel at a given highway speed because of it running a few hundred rpms faster, might actually let the V4 mode produce just enough greater hp than the 3.73 would at the same speed to actually maintain speed on light grades or light throttle applications that would cause the 3.73 to drop back into V8 operation for.
 
Am I reading some of these posts correctly?  Are some of you saying that you get better MPGs with the Tow/Haul engaged?  Are you serious?
 
Seems reasonable under low speed operation. I've gotta try this with the '08 5.3. Right now I'm getting about 13 around town with a lot of stop and go traffic.
 
It works better on the highway over 20 MPG. In stop and go traffic it may not help, but it's worth a try. Let us know.
 
did anyone confirm this?  I have a 2007 4x4 with 5.3L,  I run 15 to 16 on highway....

other question, do all have the V4 mode?  I don't notice any change in mine running down the highway...
 
Read the link those are the guys that owned 07 and tried it

MS03 2500 said:

Bigguyokie said:
did anyone confirm this?  I have a 2007 4x4 with 5.3L,  I run 15 to 16 on highway....

other question, do all have the V4 mode?  I don't notice any change in mine running down the highway...

 
And all these years guys have been disabling AFM because the mileage sucked & they had oil issues when it kicked down into V4 mode. You guys must have discovered the secret.  :E:
 
Found this over on www.silveradosierra.com

Engine Control Module (ECM)
The engine control module (ECM) is responsible for the management and control of all engine functions. Each ECM comes equipped with a specific set of software/calibrations designed for that engine and vehicle application. The ECM will determine engine operating parameters, based upon information from a network of switches, sensors, modules and communication with other controllers located throughout vehicle. Internal to the ECM is an integrated circuit device called a low-side driver. The low-side driver is designed to operate internally, like an electronic switch. An individual low-side driver controls each valve lifter oil manifold (VLOM) solenoid. When enabling conditions for V4 mode are met, the ECM will command the low-side driver to ground each VLOM solenoid control circuit, in firing order sequence. Internal to the low-side driver is a fault detection circuit, which monitors the solenoid control circuit for an incorrect voltage level. If an incorrect voltage level, such as an open, high resistance, or short to ground, is detected, the low-side driver, along with the fault detection circuit, will communicate the condition to the central processor in the ECM. The ECM will then command a return to V8 mode, set a corresponding DTC, and illuminate the malfunction indicator lamp (MIL) on the instrument panel.

Cylinder Deactivation Inhibit Reasons
Listed below are the powertrain conditions that will inhibit V4 mode, while operating under light load driving conditions:

? Engine manifold vacuum low

? Brake booster vacuum pressure low

? Accelerator pedal position rate of increase too high, electronic throttle control

? Accelerator pedal position too high, electronic throttle control

? Ignition voltage out of range

? Engine oil pressure out of range

? Engine oil temperature out of range

? Engine RPM out of range

? Transmission gear incorrect

? Transmission range incorrect

? Transmission gear shift in progress

? All cylinders activated via scan tool output control

? Minimum time in V8 mode not met

? Maximum V4 mode time exceeded

? Engine oil aeration present

? Decel fuel cutoff active

? Fuel shut-off timer active

? Minimum heater temp low, HVAC system

? Reduced engine power active, electronic throttle control

? Brake torque management active

? Axle torque limiting active

? Engine metal over temperature protection active

? Catalytic converter over temperature protection active

? Piston protection active, knock detected

? Hot coolant mode active

? Engine over speed protection active

? Fault Active or Fault Pending--cylinder deactivation is disabled for the following faults:

- Brake Booster Vacuum Sensor

- Manifold Absolute Pressure Sensor

- Engine Oil Pressure Sensor

- Engine Coolant Temperature Sensor

- Vehicle Speed Sensor

- Crankshaft Position Sensor

- Engine Misfire Detected

- Cylinder Deactivation Solenoid Driver Circuit
 
The gas mileage is a little less with Tow Haul mode while towing, but your transmission will thank you. I notice the transmission temps stay cooler with tow haul mode than without using it.
 
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