does my mpg seem right

[hoe]

Man, i'm getting under 10 mpg at the moment. only 250 miles a tank. im all city driving as well in my 01 kon 2wd. Just put in a new fuel filter, spectre CAI and changed plugs and wires(MSD Ignition) this weekend, hoping for any gain. How am I so far off from u guys? I would be stoked for 12.5 MPG!!

Terrible. My vortec max, high compression 6.0 engine, in my 2wd, and 3.73 gears gets 14 city, and 18.5 hwy. I can explain why none of your mods has helped thus far.

This goes to all the people in this thread who has terrible gas mileage. Im just sick of people being content with it.... SWITCH to NEW 02 sensors, preferably new ACDELCO units, or even the Autozone Bosch will get your mileage back as day one off the lot. 02 sensors FAIL people, they die... You put a new one, and after about 30k miles, the readings slow down, the puleses to the pcm, or stock tune computer to calculater your AFR or air fuel ratio. All this is done using the front 2 narrow band oxygen sensors.

From 1st hand experience, You may get a CEL for 02 maybe 2% of the time after they are completly dead. Meaning it WILL NOT throw a code. You think its working fine, and its not. Its reading slowly. Giving you decreased mileage and performance.


Alot of people say BB tune or custom tunes, yes, they change signals interpretation of the stock 02 sensors. (The front 2 calculates the gas, only ones you should ever change) But guess what, bad 02 when a custom BB tune or other, will still be crap output and mileage.

The stock pcm tune, is expecting that 02 to give the right feedback in microseconds. Old 02s with mileage 70k plus are very very very very lazy, giving low fuel mileage and sluggish-ness.

ITs 2 things that kills mileage on any vehicle. 02 sensor feedback and egr problems/codes.

My humble 2cents if it means anything. Sorry for the rant, Im just a performance gear head.

 

[afpj]

I doubt I've had bad O2 sensors off the lot when bought new 8 +yrs ago, as this mileage has been the same. I assume, therefore, you are referring to the situation when gas mileage drops over time? If you change the O2 sensors, based on your description of things, should you disconnect the battery for a little to reset the computer? Good info to know.

 

[MikeTheApeman]

I've got an AWD 'hoe, do probably 75% city driving. Stock everything except for an AFE drop-in filter. I average 15.6MPG. See a red light ahead? Let off the gas early. Accelerate slowly. If I'm stuck in traffic waiting for a light, most of the time I don't even hit the gas when traffic moves, I just let the idle carry me along slowly. Hell, on the highway up to Maine from NJ two weeks ago, I averaged 18.1MPG @ 70MPH with a full load in the truck. (The mrs, myself, hitch hauler with 2 totes and a cooler, luggage, 2 Yorkies, a Yellow Lab, and a Husky.)

I'm not saying there aren't mechanical issues causing bad MPG. I am saying that driving style contributes as much, is not more.

 

[Brick]

Recalculted on the last tank and I was around 11.6. Going to test again on this tank as this will show my new mods (Cai, new plugs, fuel filter,and msd ignition). I get what people are saying about driving style but I promise u I am not a race around town in the Kon type of Guy. I only get in it when rare situations call for it. I never heard that the o2 could cause bad MPG, but if that's true I might run a can of seafoam through her then change the o2 after. I'm not expecting 20+MPG, but I don't think 13-15 is out of line to ask for.

 

[My01yuk]

Terrible. My vortec max, high compression 6.0 engine, in my 2wd, and 3.73 gears gets 14 city, and 18.5 hwy. I can explain why none of your mods has helped thus far.

This goes to all the people in this thread who has terrible gas mileage. Im just sick of people being content with it.... SWITCH to NEW 02 sensors, preferably new ACDELCO units, or even the Autozone Bosch will get your mileage back as day one off the lot. 02 sensors FAIL people, they die... You put a new one, and after about 30k miles, the readings slow down, the puleses to the pcm, or stock tune computer to calculater your AFR or air fuel ratio. All this is done using the front 2 narrow band oxygen sensors.

From 1st hand experience, You may get a CEL for 02 maybe 2% of the time after they are completly dead. Meaning it WILL NOT throw a code. You think its working fine, and its not. Its reading slowly. Giving you decreased mileage and performance.


Alot of people say BB tune or custom tunes, yes, they change signals interpretation of the stock 02 sensors. (The front 2 calculates the gas, only ones you should ever change) But guess what, bad 02 when a custom BB tune or other, will still be crap output and mileage.

The stock pcm tune, is expecting that 02 to give the right feedback in microseconds. Old 02s with mileage 70k plus are very very very very lazy, giving low fuel mileage and sluggish-ness.

ITs 2 things that kills mileage on any vehicle. 02 sensor feedback and egr problems/codes.

My humble 2cents if it means anything. Sorry for the rant, Im just a performance gear head.

How do you check the O2 sensors to see if they are bad? I have 109K on the clock, so I would assume they need to be replaced.

 

[hoe]

How do you check the O2 sensors to see if they are bad? I have 109K on the clock, so I would assume they need to be replaced.

The average 02 last 30k miles. Trust me, its reading slow, they never throw a code for the front, unless pcm gets 0 readings. They are like sparkplugs, when it drives like shit, change em. But they decrease after a certain number of miles. Ac delco unit is good, atleast 60k in my book, but if I remember they call for 30k intervals as well for quicker response to the pcm. Climates, position of 02 all has to play a role as well.

I know cause I run around town all the time with 5bucks in the tank I know my mileage is dead on everytime, Im not a faint driver either, as a matter Im aggressive. I calculate my stuff like routine.

To get to fully answer your question specifically: The only way to see is to read the milivolts the 02 sensors wires are outputing to the pcm. This can be done with a DMM + timer, or observation. To better tell, you can have hp tuners hooked up to your obd2 connector or monitoring handhelds or other software. But one that records each sensor, and its output what its doing while the vehicle is running.

But yes, I think you see that its a important sensor now. Which is all I wanted to do, If someone thinks their 02 is fine, dont listen to me & still keep thinking like that. Your wrong, everything degrades, including life. For the 0miles performance from stock, yes, a new delco unit will work well. If also had very good output from the bosch sensors. But NEVER use bosch plugs or anything else. lol

 

[JoeOmerta]

I did an experiment when i first got my yukon xl, if i accelerate keeping the rpm's below 2000, i get worse gas mileage then if i let them hit 2500 rpm's each gear. So in my experience, granny driving kills gas mileage

 

[k5blzt]

I would be interested to know if you guys are just using you computer to tell you the mileage, or if you are doing the math. We have an 03 Tahoe that the computer always says 14mpg average...no matter what...ever since we bought it. I am **** and write down the mileage every time I get gas. When I calculate it out I am usually around 15.5mpg, but have gotten up to 19mpg on long trips. For whatever reason, the onboard average mileage on mine seems to be stuck on 14mpg and I just ignore it. My buddy has an 06 Tahoe that seems to be stuck a 15.2mpg. Try calculating your mileage over several tanks and see what you come up with.

 

[yukondoit]

I would be interested to know if you guys are just using you computer to tell you the mileage, or if you are doing the math. We have an 03 Tahoe that the computer always says 14mpg average...no matter what...ever since we bought it. I am **** and write down the mileage every time I get gas. When I calculate it out I am usually around 15.5mpg, but have gotten up to 19mpg on long trips. For whatever reason, the onboard average mileage on mine seems to be stuck on 14mpg and I just ignore it. My buddy has an 06 Tahoe that seems to be stuck a 15.2mpg. Try calculating your mileage over several tanks and see what you come up with.

x2

 

[Brick]

no my kon doesnt have that in the computer, or if it does im unaware of it, i do it by math. this last tank was a lil better (11.6) hopefully the current one is even better. guess i may have to look into the o2 sensor. is their 2 in the front or only one? seems to be right around $55 for the sensors i found. would make sense to run a can of seafoam through the gas tank and pc valve before i change the sensor, right?

 

[hoe]

no my kon doesnt have that in the computer, or if it does im unaware of it, i do it by math. this last tank was a lil better (11.6) hopefully the current one is even better. guess i may have to look into the o2 sensor. is their 2 in the front or only one? seems to be right around $55 for the sensors i found. would make sense to run a can of seafoam through the gas tank and pc valve before i change the sensor, right?

Mine is a 01 like yours. 00-02 has NONE like ours. 03-06 has the different cluster with the gas economy reader. Which is not accurate IMO. I had a 85 cadillac with that feature, going down hill on any decline its good got 100mpg, uphill or load it got 0mpg according to the pcm. All that monitoring is good, but its not exact. Its actually telling you REAL TIME Mileage. Like in microseconds. Not the average.

Yea, seafoam is good, especially if you have a EGR system on any engine. Im happy my LQ9 does not utilize it. Under my intake manifold was CLEAN. The 5.3 on the other hand is black from carbon entering the egr from the intake. Seafoam will help burn that off the cylinders. But not gain you mileage.

Seafoam would be a waste for your case in my book. The truck has 4 o2s total. 2 of them before your cat converters; and 2 after them. The front 2 are important. Its the ones that effect your mileage by reading your exhaust gas, to tell the computer or pcm your exhaust air fuel ratio. If that is being calculated wrong or slowly, your mileage plumbeths. Change the front 2 02s and be done with it. Then report your findings, and how the truck drives afterwards.

---------- Post added at 05:12 PM ---------- Previous post was at 05:04 PM ----------

I guess I am being useful to this forum. Okay let me break things down that KILLS GAS MILEAGE.

1) Front two 02 sensors
2) Stuck or bad EGR valve
3) Plugged CAT Converter (WHICH THE 02 monitors as well [rear sensors]) <<This is physical, just change the cats


My mileage is always calculated by hand. My vortec max uses premium 93 and runs well. I actually just reset my trip after each gas fillup. I calculate when Im runing low mentally. Its not hard people, dont need a computer for that. Its many times I put 1.7gallon in my truck and got to where Im going while driving very spirited. I change my behaviors if Im city or hwy. People need to drive with anticipation in mind, someone mentioned that above somewhere. Dont hit the gas hard, to slam on it, a few meters ahead of you again.

 

[afpj]

How hard is it to change the front O2 sensors? It's too dark outside when I get home from work, so won't have a chance to look for another week. I assume they're accessible from the engine bay, or crawl under the car? Do they just unscrew like a sparkplug? Since we have 125k miles, I'm expecting some rust or something...can you spray with Wd40 first to soak the threads? Thanks for any info.

 

[yukonjacks]

I get between 11 and 11.5 local driving, but then again I'm traveling on hills, and winding roads. for those of you bragging about 14+ your local driving is like my hiway driving. heck when you guys say your going down the road to a store, its probably 30 miles away on straight flat roads with no stops. For me down the road maybe 3 miles up hill both ways, with 1 stoplight and 2 stop signs. Personally, if your not happy with the gas milage buy a friggen Ford Fiesta.

---------- Post added at 11:23 PM ---------- Previous post was at 11:18 PM ----------

blue have you changed to performance plugs or wires changed the fuel filter etc? after doing all the above and magnaflow and airbox/filter/tube mod i get 18mpg avereage
i do more hwy than in town though

Its hard to accept that your getting 18 mpg in around town in Canada, Dont they use liter and kilometers. You must have one special magical rig to be gettin that much.

 

[JKmotorsports]

When I first bought my truck, it was fully stock and I was getting around 16mpg mixed city/hwy, with the stock 3.73 gears.
If you still have the original o2 sensors, replace them with new ones, but just the front two. If your sensors are old, you should gain some mpg with a fresh set of o2s that can properly monitor and adjust your engine's afr.

 

[jpaeltz]

Yep. pretty consistent, I average about 14 living in Dallas.

 

[afpj]

What brand of O2 sensor would you guys recommend? OEM? autozone special? ebay special? Thanks.

 

[bluekon]

So turns out Guy I bought my truck from was full o shit he told me all the maintanince had been done found the rear diff fluid needed to be changed so I changed that today and I took a peak to find what looka to be OEM sparkplugs still in the truck at 144k miles so I replaced those with some fresh acdelco plugs we will see if mileage goes up

 

[gtbigup01]

You should be getting better than that. I get 13.6 with military base stop and go shot trips driving, with the ocasional walmart run. 12.5 seems too low to me especially for a 5.3

 

[bluekon]

just thought id update after the plugs and diff fluid change my first 1/2 tank i got 13.6 mpg

 

[My01yuk]

That's more like it.