5.3 v8 w/ 3.73 ratio

alltimeqb

Original poster
Member
Dec 4, 2011
6
Took a drive from Detroit area to Chi-Town. First stop for gas turned out just over 18 mpg. Nav said I was doing 76 mph for most of that leg.

Heading back today. If the wife doesn't get antsy, I'll run 'er about 66 - 69 mph for a good stretch and see how much it improves.

:undecided: In case anyone's interested.
 

HARDTRAILZ

Moderator
Nov 18, 2011
49,665
Good idea. Will be interested to see your findings for speed difference.
 
Dec 4, 2011
520
alltimeqb said:
Took a drive from Detroit area to Chi-Town. First stop for gas turned out just over 18 mpg. Nav said I was doing 76 mph for most of that leg.

Heading back today. If the wife doesn't get antsy, I'll run 'er about 66 - 69 mph for a good stretch and see how much it improves.

:undecided: In case anyone's interested.

Always interested in actual on the road results. Just remember speed isn't the only deciding factor. Things like headwind/tailwind, temperature, road conditions, stop and go's and other tangibles such as vehicle load. If you could comment on these things as well as reporting actual mileage it would be appreciated. This is also why over the long run these factors tend to even themselves out.

Thanks for the effort. :thumbsup:
 

n0kfb

Member
Dec 8, 2011
104
I've noticed that at highway speeds, a change of 5 miles per hour changes my fuel economy by 1 mpg.

-- Dan Meyer :coffee:
 

Boricua SS

Member
Nov 20, 2011
3,080
Ohio
On my trip to Indy for the big midwest meet earlier this year, I was shocked at my mpg's... its 70 mph on the ohio turnpike, so for the first leg (about 2 and half hours) I was doing 70, and once into Indiana, the speed limit went up to 75 mph.. and I got 18.2 mpg in my 6.0L V8.. on the way back home, (doing 75 mph the whole way), I got 19.1!!! FTW! Mind you, I am tuned, have a CAI, E-Fans, and full exhaust.. so about as much mpg's as I'm gonn get outta her.. but city mpg's.. forget about it.. anywhere from 9-13 mpg's depending on how I'm gettin on it... and those are all calculated real driving numbers..
 

Busterbrown

Member
Dec 4, 2011
253
n0kfb said:
I've noticed that at highway speeds, a change of 5 miles per hour changes my fuel economy by 1 mpg.

-- Dan Meyer :coffee:

I don't think that fuel usage at highway speeds is linear. I'm pretty sure after 65 mph, the ratio becomes more exponentially driven. When your up to 80 mph, consider a 5-7 mpg loss the norm. Maximizing mileage on our trucks usually involves a strict 60-65 mph, steady-driving pattern.
 

06Envoy

Member
Dec 4, 2011
419
I think this is true...


With my DoD 5.3l, I've noticed that at 100kph (60mph) I get about 22mpg according to my DIC, and I'm pretty sure I'm running on 4cyls.
However if I go over 105kph (65mph) then it drops down to about 17mpg, I figure that its running on 8cyls.
 
Dec 4, 2011
520
Busterbrown said:
I don't think that fuel usage at highway speeds is linear. I'm pretty sure after 65 mph, the ratio becomes more exponentially driven. When your up to 80 mph, consider a 5-7 mpg loss the norm. Maximizing mileage on our trucks usually involves a strict 60-65 mph, steady-driving pattern.

You are correct, the wind resistance increases exponentially as you go faster, and of course with added ground wind (either of the tail or head on variety) it will make a difference.
 

MichEnvoyGuy

Member
Dec 3, 2011
523
I just got depressed reading this thread...my 2002 I-6 (with the 4.10's alas so I know that will make a difference) gets 16.5mpg highway these days going 75mph :frown: Depressing to know I'd be getting better mpg's with the small block. Oh well...
 

alltimeqb

Original poster
Member
Dec 4, 2011
6
Good points about the variables.

Just the wife and I plus the dog and two small overnight bags.

On the way there, I was all about getting there so when I hit traffic near Chicago I was using the accelerator but keeping my distance... almost had a multi-car pile up on the Ryan :eek:

For the trip back I was set at 68 mph for the bulk of the 324 miles. This calc includes the entire trip, through suburbs, stop & go through downtown and a detour around rush hour in Detroit.

MPG = 20.8. Nearly a 3 mpg gain so if I kept it below 65 I'd have to agree the 5-7 mpg swag is pretty much spot-on.

There's an added bonus: every single truck I came up on was doing 1 or 2 slower so there was a lot less 2-lane dance at 68 mph, which for my money is worth it!

FWIW - I when I was passing and needed to pick up the pace a bit I never went over 73 mph.
 

TGFB87

Member
Dec 27, 2011
14
With my 5.3L equipped TB, it is not uncommon to average 19.5-21 MPG on a long trip. Rather consistent during my Chicago-Orlando trips with the family. I just make sure the K&N is clean, tire pressure is good, and I change the oil before the trip. Oh, and I throw a can of Techron into the tank at every oil change.

Too bad around town, I still average 15-16.
 

alltimeqb

Original poster
Member
Dec 4, 2011
6
That's an excellent rate around town. I figure between 13.5 to 14 mpg around town for me.
 

Jkust

Member
Dec 4, 2011
946
I've owned three 360's all AWD with the 5.3 and 3.73's and currently have two of those and both have the DoD (while the first one didn't have DoD). I can give you mileage numbers till the cows come home towing, in town, highway, loaded, unloaded. What it all comes down to for me and my substancial experience with the 5.3 is simply the right foot. If I go even 65mph, I get typical bad v8 mileage. Keeping it at 61mph, all highway the 9-7 gets just over 20mpg and the Identically equipped Rainier gets 22mpg but the Rainier gets worse in-town mileage. I don't know why that is but it started when the Rainier got a new ECM. Afterward it felt like the Rainier got a tune (which it didn't but the throttle response is awesome now) but the intown mpg's dropped. When I am towing however the wind plays a big role. A good tailwind, and my towing mileage goes way up.
 

Spong

Member
Dec 12, 2011
59
Tires can also make a difference. I replaced the OEM Continentals on mine with Destination A/Ts before the TB even had 10 miles on it. I also disengaged the DOD. I would get 16 to 19 depending on conditions running 70-75 mph. I now have Dueler Revo A/Ts which are a little more aggressive than the Destinations and I get about the same. I would say an average of 17 overall on the interstate. My summer wheels have a more highway friendly tire, Geolander HT/S G052 but they are on heavier chrome wheels. Still get about the same mpg.
 

alltimeqb

Original poster
Member
Dec 4, 2011
6
Tires can make a big difference. I'll probably put more aggressive tires on at the end of next summer. I'm leaning toward building out an offroad rig. (I'll have to balance that against the money I'd like to spend on my motorcycle ;-)
 

dirtbikingdad

Member
Feb 13, 2012
8
TGFB87 said:
With my 5.3L equipped TB, it is not uncommon to average 19.5-21 MPG on a long trip. Rather consistent during my Chicago-Orlando trips with the family. I just make sure the K&N is clean, tire pressure is good, and I change the oil before the trip. Oh, and I throw a can of Techron into the tank at every oil change.

Too bad around town, I still average 15-16.

Wow! My 2WD 2004 with 5.3 gets 13 or so in town and 16.5 on the road doing 75 or so. And I had to go with PCMforless just to get that.
 

Mark20

Member
Dec 6, 2011
1,630
Changing truck department here: Shortly after getting my Silverado (5.3L Active Fuel Management w/ 3.73) I took it on a long 800 mile trip. Average was 20.9 MPG, sticker says 21 MPG. When that engine drops to 4 cylanders the instantaneous MPG shoots up to the 30's and that makes a big difference. I can nurse 21-22 out of the Envoy but hills really kill that.
 

TGFB87

Member
Dec 27, 2011
14
I will say that in my TB, once I go over 70, the average starts to drop very quickly. 65MPH is pretty much the sweet spot between speed and fuel economy. At least from my experience.
 

Jkust

Member
Dec 4, 2011
946
Mark20 said:
Changing truck department here: Shortly after getting my Silverado (5.3L Active Fuel Management w/ 3.73) I took it on a long 800 mile trip. Average was 20.9 MPG, sticker says 21 MPG. When that engine drops to 4 cylanders the instantaneous MPG shoots up to the 30's and that makes a big difference. I can nurse 21-22 out of the Envoy but hills really kill that.

The two things on the Silverado's I wished the tv's had is the DOD indicator that turns on in 4 cyl mode and the trans temp in the DIC. Edit: I'll add to that the instant mpg in addition to the average mpg it already has.

I'm trying to figure out why every single morning my DIC mileage in the 9-7 to work on the 22 mile trip differs. Some days its lucky to be at 17 and other day's i'll arrive and it will be on 22. I drive the same way every day. As crazy as it sounds the morning after a fill up always at the same gas station, the mileage is the highest.
 

RayVoy

Member
Nov 20, 2011
939
Everyone who answers the "what do you get for gas mileage?" question............................... is a liar :raspberry: .........................................................including me.
 

MDBT

Member
Jan 26, 2012
223
Common posts in MPG threads:

I'm getting X mpg which is very low, I offer no additional useful information, please tell me how to fix it immediately and without costing me anything.

I don't know what's wrong with your car, I'm getting better mpg than the highway sticker rating (secretly he only got that once and it was because he was drafting his grandmother's car at 48 mph on the highway)

I'm getting a similar mileage, you must be ok.

I'm getting excellent mileage, praise me and beg to learn my secrets.

I got really bad mileage once, here's what my dealer told me was wrong and after I paid him 1200 dollars mine shot up 2mpg more, you should do this too.

8 posts with people chiming in without any useful information, just to share their mileage.

3 posts with people running completely different components telling you what they get, as if it's relevant in any way.

Someone to discuss how it's all in the driving technique, and that you're all getting lower mileage because you're not as conservative a driver as he.

Someone else to tell you how the temperature, seasonal fuels, tire pressure, maintenance, and the like effect the mileage and so comparisons are meaningless.

Someone to post that people need to stop worring about 2mpg differences in mileage when you're driving around vehicles that weigh nearly 5k pounds and have almost 300hp.

And last but not least one smart-ass who wrongly assumes he's any better than the rest of you to post this.


I've put all of 70 miles on mine since I got it a few weeks ago, so I'm actually just watching this thread to learn since it's relevant to my driveline, but I thought I'd have a little fun while observing :wink:
 
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am-radio

Member
Apr 24, 2012
178
Jkust said:
I've owned three 360's all AWD with the 5.3 and 3.73's and currently have two of those and both have the DoD (while the first one didn't have DoD).

How can I tell if my 06 Envoy Denali has DoD?
 

Denali n DOO

Member
May 22, 2012
5,596
am-radio said:
How can I tell if my 06 Envoy Denali has DoD?

I believe there is an "M" in the serial number. Most likley is DOD.
 

am-radio

Member
Apr 24, 2012
178
My 8th digit is an M. What exactly is DoD? I'm assuming some sort of fuel management system. Is there any benefit to this, or is it more just a sales pitch? How can I tell if this is activated or if I'm supposedly getting better fuel economy?
 

Denali n DOO

Member
May 22, 2012
5,596
am-radio said:
My 8th digit is an M. What exactly is DoD? I'm assuming some sort of fuel management system. Is there any benefit to this, or is it more just a sales pitch? How can I tell if this is activated or if I'm supposedly getting better fuel economy?

Displacement On Demand- shuts down 4 cylinders when it doesn't need them like cruising down the hiway. I've had trips as low as 10.5L/100km, don't think I'd get that without DOD. I think it can be shut of with a tune. I like the DOD.
 

am-radio

Member
Apr 24, 2012
178
I've seen 10.5 to 11 liters per 100 km a couple times on the highway, but for very short times. I'm guessing at 115-120km/hr, I'll never get that. I'd probably have to do 95 or 100 km/hr.
 

RayVoy

Member
Nov 20, 2011
939
am-radio said:
How can I tell if my 06 Envoy Denali has DoD?
Actually, I don't think you have a choice.
All '06 V8s would have DOD by default.
 

mnypitTBEXT

Member
Jan 29, 2012
133
I know tis is a little old, but thought I would throw my info in there. We made a trip from Daytona Beach to Savanah and when I was driving, set the cruise at 70mph most of the way, I squeezed 22.8 out of her with 114k on the clock. My wife drove home and we only got 18.3. Made a trip to our cabin in NC and with me driving I was able to get 19.2, but we are at 4000ft, so very mountainy.

We get about 14-15 towing the boat across the state on highways.

My wife drives it regularly, and mixed driving and back and forth to work we usually get about 17-18 on average. Usually every tank of gas includes minimal boat towing, maybe 15 miles or so. Kills the average.

Incidently, my work car, a Jeep Patriot with a 4 cylinder and that absurd CVT transmission that always feels like its slipping(company made the choice, not me) and I get about the same. It was in the shop this week and I have had a Buick Enclave rental. Drove to Tampa yesterday and was sitting right at 29mpg on the last tank of gas.
 

Jkust

Member
Dec 4, 2011
946
mnypitTBEXT said:
It was in the shop this week and I have had a Buick Enclave rental. Drove to Tampa yesterday and was sitting right at 29mpg on the last tank of gas.

Thats amazing given the top EPA average is up to 24 on the highway. The one's I've driven, I barely squeeked 21 mpg on a tank on the 2wd version nearly in line with the 5 or six folks I know that own them.
 

am-radio

Member
Apr 24, 2012
178
I average 13 - 14 liters/100 km city highway driving. Towing a 2800 lb tent trailer at 110 to 120 km/hr I was averaging 16 - 18.5 liters/100 km.
 

mnypitTBEXT

Member
Jan 29, 2012
133
Jkust said:
Thats amazing given the top EPA average is up to 24 on the highway. The one's I've driven, I barely squeeked 21 mpg on a tank on the 2wd version nearly in line with the 5 or six folks I know that own them.

Yeah, that is more what I expected, but on a nice flat long run, apparently you can achieve more. I wonder sometimes though, if it has more to do with when you pump shuts off. Some shut off earlier than others. The majority of the time I was sitting right around the 23 to 24 they claim. The 29 I got on the last tank I ran through it was probably me living 5 minutes from the interstate and the places I was going also less than 5 minutes from the interstate, and making the run on a Sunday with absolutely no traffic and me in absolutely no hurry, driving around 60mph all the way. I am guessing normal everyday driving would be less, especially with my wife driving. Not that she drives crazy or anythign, but she refuses to use the cruise control, and I use it going everywhere.
 

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