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Better Gas Mileage Mods

Alex Campomizzi

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Tom2015 New Member

Tom2015

Posted
Posted
4 hours ago, tanner709 said:

What engine? what cab, what box, what gearing, what trans?

 I struggled to maintain 10-11L/100km when my truck was stock around 100-110km/h with cruise or manual intervention. '16 crew cab short box LT z71, 5.3L with 3.43gearing bone stock 6 speed

 

Also, that 6.5L/100km is only for a certain mileage (the largest history being 650km). I understand you may have maintained that during the whole trip but I find it hard to believe.

 

Personally I think I can drive better and smarter than cruise can, therefore you can actually save gas if you have the patience and control.

5.3L non flexfuel, doublecab, 6.5ft box, 3.42 gears and 6 speed auto trans. This was with a set of Nitto 420S tires in 305/40R22. Very easy on the throttle and highway cruising for 300-600 km at a time typically 100-110km/h. Everything on the truck is stock other than exhaust which shouldn't make a difference.

tanner709 Enthusiast

tanner709

Posted
Posted
50 minutes ago, Tom2015 said:

5.3L non flexfuel, doublecab, 6.5ft box, 3.42 gears and 6 speed auto trans. This was with a set of Nitto 420S tires in 305/40R22. Very easy on the throttle and highway cruising for 300-600 km at a time typically 100-110km/h. Everything on the truck is stock other than exhaust which shouldn't make a difference.

So no exhaust valve either huh. That's impressive, better than half of what I burn...

  • 1 month later...
Tom2015 New Member

Tom2015

Posted
Posted
On 12/1/2017 at 2:09 AM, tanner709 said:

So no exhaust valve either huh. That's impressive, better than half of what I burn...

Its the borla exhaust from the dealer it does have the valve in it.

  • 3 weeks later...
cowpen Enthusiast

cowpen

Posted
Posted
On 11/30/2017 at 1:25 PM, Grumpy Bear said:

Decel tables on new stuff shuts off the fuel on coast down. N is not required. Uses more fuel and in most states is illegal. Why? Because the majority KNOW its dangerous.  California Section 21710:

The driver of a motor vehicle when traveling on down grade upon any highway shall not coast with the gears of such vehicle in neutral.

Agree with you about shifting into neutral. However, grade braking is still the default run condition for our trucks which is using the friction of your engine to slow the vehicle in a coasting situation - even on flat ground. Watch the tach as the gears drop while you coast.

 

If you're on flat ground and don't need grade braking, you can disable it by holding the tow mode button for 5 seconds. In this mode, when you coast, the engine idles and the tranny is effectively disengaged and free wheeling. You can coast a LOT further and really rack up some MPG's this way if you anticipate stops or slowdowns.

 

Maxing out on efficiency with a screaming 6.2L is almost as fun to me as burning rubber & chirping 2nd. It's amazing to me the technology that allows both in the same truck. Kudos to the GM engineers!

tanner709 Enthusiast

tanner709

Posted
Posted
1 hour ago, cowpen said:

Agree with you about shifting into neutral. However, grade braking is still the default run condition for our trucks which is using the friction of your engine to slow the vehicle in a coasting situation - even on flat ground. Watch the tach as the gears drop while you coast.

 

If you're on flat ground and don't need grade braking, you can disable it by holding the tow mode button for 5 seconds. In this mode, when you coast, the engine idles and the tranny is effectively disengaged and free wheeling. You can coast a LOT further and really rack up some MPG's this way if you anticipate stops or slowdowns.

 

Maxing out on efficiency with a screaming 6.2L is almost as fun to me as burning rubber & chirping 2nd. It's amazing to me the technology that allows both in the same truck. Kudos to the GM engineers!

What?

Grade braking conditions will only be active when the brake is depressed (edit: or a speed is set via cruise). Pretty sure that's condition #1. At no other time will it activate.

 

You may stay in what gear you're in when you let off, until a higher or load is detected. I think that's the rev hang you're talking about

cowpen Enthusiast

cowpen

Posted
Posted
6 minutes ago, tanner709 said:

What?

Grade braking conditions will only be active when the brake is depressed (edit: or a speed is set via cruise). Pretty sure that's condition #1. At no other time will it activate.

 

You may stay in what gear you're in when you let off, until a higher or load is detected. I think that's the rev hang you're talking about

The terminology is confusing. Maybe I should have said "powertrain grade braking" which doesn't actually involve the brakes? All I know is I can coast a lot farther without losing momentum by turning it off.

 

See https://gm.oemdtc.com/5611/normal-mode-powertrain-grade-braking-feature-2013-2016-cadillac-chevrolet-gmc

 

 

tanner709 Enthusiast

tanner709

Posted
Posted
4 minutes ago, cowpen said:

The terminology is confusing. Maybe I should have said "powertrain grade braking" which doesn't actually involve the brakes? All I know is I can coast a lot farther without losing momentum by turning it off.

 

See https://gm.oemdtc.com/5611/normal-mode-powertrain-grade-braking-feature-2013-2016-cadillac-chevrolet-gmc

 

 

I'm not sold.I'd be curious to see if that's still the case (the coasting distance) on the same road at the same speed with it on and with it off.

 

6th (or 8th) gear, same rpm and speed.

 

quoted from the article you posted;

"For grade braking to activate it requires the driver to apply steady brake pedal pressure to maintain desired speed while driving on a downhill grade. The vehicle’s modules monitor the amount of brake pedal apply, vehicle deceleration rates, and other factors to determine if normal mode powertrain grade braking is necessary. When the feature activates for the first time that ignition cycle, the DIC will display “Grade Braking On” or “Grade Braking Active” and you will notice the transmission down shifts and engine RPM increases. At this point, if the brake pedal is released the transmission will hold the current gear. If additional engine/transmission braking is needed to help maintain desired speed, reapply steady brake pedal pressure and additional down shifts may occur."

cowpen Enthusiast

cowpen

Posted
Posted

Try it. There's a significant difference. Watch the tach.

tanner709 Enthusiast

tanner709

Posted
Posted
8 minutes ago, cowpen said:

Try it. There's a significant difference. Watch the tach.

Definitely ! worth a try.

 

I actually utilize the tow/haul grade braking a lot as it helps on some of the hills here and I drive a lot of highway so there a lot of 60-70mph to 0 situations. @ 30k miles my brake pads are next to new - the technician was very surprised at my last service.

cowpen Enthusiast

cowpen

Posted
Posted
1 minute ago, tanner709 said:

Definitely ! worth a try.

 

I actually utilize the tow/haul grade braking a lot as it helps on some of the hills here and I drive a lot of highway so there a lot of 60-70mph to 0 situations. @ 30k miles my brake pads are next to new - the technician was very surprised at my last service.

I totally get it for hills. But the only hills around here are interstate overpasses.

 

FWIW, I'm new to this truck. Mine's an 8 spd. Don't get me wrong - this thing coasts very well without changing anything. But it coasts even better with the "grade" setting off.  I'm coming out of an 05 Nissan Titan, which didn't disengage the drive train at all when coasting. You can literally feel it marching down through the gears. I'm sure that saves the brake linings, but why waste energy by using an engine brake on a flat road? I was always envious of my wife's Jeep Commander; you can take your foot off the gas at 60 and still be running 50 a mile down the road.

 

I've got nearly 200K trouble free miles on the Titan, and I only replaced the front pads once. Still on the original rears. Honestly a great truck IMO. I would have bought a 2018 if the new body styles weren't so butt-ugly!

 

  • 4 months later...
Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
On ‎11‎/‎21‎/‎2017 at 6:58 PM, KARNUT said:

If there was a way to get better gas mileage out of these trucks other than drive slower, the builders ( manufacturers) would do it. 

I took this at face value first time I read it because it 'sounds right'. Then I made a series of small modifications to mine this spring for 'other' reasons and got a happy surprise. Not just a measurable  bump in mileage but a repeatability there was no way to expect. Look at the last 15 tanks of the blue line and you will see what I mean compared to her entire history of 64,912 current miles. All but 8,851 miles of her life is on this chart. 1,300 miles were on the clock when I bought her and the remaining miles lost when my hard drive fried unbacked up. Each of the two major bumps are tied to ambient temperature increases. 

 

What did I do? Somethings the manufacture will not do. Three things actually. Lower the operating temperature of the entire system via a colder thermostat (170 F / 76 C) and removal of the transmission thermal by pass valve's guts. Change all power train fluids to Red Line POA/Ester fluids and the oil from 5W30 to 0W20.

 

Why won't they do them? These three items work against Nox emissions under WOT situations. I can't tell you the last time I had her WOT. 

 

Since last summer I've actually increased my average road speed about 5 mph and deflated my tires 5 psig to a more comfortable level both of which work against this result. 

 

She's got big numbers before but not so many and not with such consistency. A small part of consistency came from a level stance that makes it easier to get consistent fills but those modifications alone have been done for quite some time without producing this result.

 

So I guess an amended statement would read, " If there were a means to get better mileage from our trucks that they were WILLING to do they would have done it". Then there's this. What they do today guys like Smokey Yunick was doing decades ago.

 

The new question then is...What are you willing to do they are not to get better fuel efficiency?  

 

PeppersMPGHistory.png

Nasty Senior Enthusiast

Nasty

Posted
Posted
16 minutes ago, Grumpy Bear said:

I took this at face value first time I read it because it 'sounds right'. Then I made a series of small modifications to mine this spring for 'other' reasons and got a happy surprise. Not just a measurable  bump in mileage but a repeatability there was no way to expect. Look at the last 15 tanks of the blue line and you will see what I mean compared to her entire history of 64,912 current miles. All but 8,851 miles of her life is on this chart. 1,300 miles were on the clock when I bought her and the remaining miles lost when my hard drive fried unbacked up. Each of the two major bumps are tied to ambient temperature increases. 

 

What did I do? Somethings the manufacture will not do. Three things actually. Lower the operating temperature of the entire system via a colder thermostat (170 F / 76 C) and removal of the transmission thermal by pass valve's guts. Change all power train fluids to Red Line POA/Ester fluids and the oil from 5W30 to 0W20.

 

Why won't they do them? These three items work against Nox emissions under WOT situations. I can't tell you the last time I had her WOT. 

 

Since last summer I've actually increased my average road speed about 5 mph and deflated my tires 5 psig to a more comfortable level both of which work against this result. 

 

She's got big numbers before but not so many and not with such consistency. A small part of consistency came from a level stance that makes it easier to get consistent fills but those modifications alone have been done for quite some time without producing this result.

 

So I guess an amended statement would read, " If there were a means to get better mileage from our trucks that they were WILLING to do they would have done it". Then there's this. What they do today guys like Smokey Yunick was doing decades ago.

 

The new question then is...What are you willing to do they are not to get better fuel efficiency?  

 

PeppersMPGHistory.png

Easier way is to run slightly smaller tire than stock and shut off afm. Atleast for me it got me better average mpg

Grumpy Bear Senior Enthusiast

Grumpy Bear

Posted
Posted
3 hours ago, Nasty said:

Easier way is to run slightly smaller tire than stock and shut off afm. Atleast for me it got me better average mpg

Quick question. Did you calibrate the speedometer of the increased wheel rpm per mile?

Nasty Senior Enthusiast

Nasty

Posted
Posted
7 minutes ago, Grumpy Bear said:

Quick question. Did you calibrate the speedometer of the increased wheel rpm per mile?

Sure did and shift points to because of the smaller diameter tire

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