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fuel mileage is horrible

stacks04

stacks04

McLovin
Messages
3,579
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Location
terryville ct
I last week I did about 70 miles of towing, and about 200 city/highway and thats about it on a tank of fuel. 23 gallons to be exact. By my calculations that is about 12 mpg. What in the hell do think is going on? I imagine i should be doing alot better. My trip down to Virgina beach last summer also only got about 15. That was all highway. My ipc speedo was broken, but now isnt and i got around to calculating things and some past trips via mileage numbers off of google maps and this is what I am coming up with. Any thoughts on this? My trip to myrtle towing my trailer is going to be costly with that kinda of mileage.
 
Not good numbers for sure.

What kind of speeds are you doing on the highway Joe? I just hand calculated a tank of 20.5 last week. Combination of City and Highway. When I tow, I generally get about 13-14 mpg. Maybe check your mileage with a GPS ??????

Do you have larger tires ????
 
RI Chevy Silveradoman said:
Not good numbers for sure.

What kind of speeds are you doing on the highway Joe? Normaly unhooked i travel at 70mph
I just hand calculated a tank of 20.5 last week. Combination of City and Highway. I wish i could come close to that
When I tow, I generally get about 13-14 mpg.
Maybe check your mileage with a GPS ??????I have verified the odometer with a gps, its dead nuts on.

Do you have larger tires ????I have 285/75/16. I always had them, just recently though i changed from the bfg to the g/y duratrac. I would not think it would hurt it that much.
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I checked my balance rates last night, the highest one was 2.7, fuel filters are brandy new as of last week, before then i would understand the poor mileage. Always run either sunoco or mobil, the 2 stations near to my house. I also run power service each tank.
 
Joe, I might lean towards fuel quality knowing your truck is mechanically sound. I have tracked every drop of fuel and mile I have put in/on my truck since the day I bought it. I have 80K worth of data. Every year I see a drop in fuel mileage during the winter due to the winter blend and an increase back to normal in the spring. My fuel mileage has remained the same since last fall. My driving habits have remained the same. I also would like to find a cause....:shrug:
 
Replace it with a 6.5 :D I'm getting 18+,

Seriously though, have a look at the injectors as that is a lot of lost mpg for Cetane, you running a Cetane + additive ?, I was getting down to 15-16 until replaced injectors 2 mos ago 160K on em, now back up to 18+.

I say + because I was doing some high speed running my last highway trip to-from Bangor/Syracuse avg 72 mpg peaking to 100 mph on occasion, running I-90, running with Ricers that could not climb the mountain with me.
 
The quality of distillates in general have gone down the crapper across the board. even heating oil i sell is dirty looking compared to five years ago. IMHO They are not refining it as good.
 
not just diesel. Gas quality has really taken a dump too. I've seen all my vehicles drop their yearly average mpg the past couple years (I keep records). I know a mechanic for atv's, snowmobiles, motorbikes, etc. and he is getting overrun with machines not running and it's all due to bad gas gumming up the carb. The ethanol isn't helping either. I'm having to practically tear the carb apart on my weedeater just about every time I try to use it. Everything gets gummed up so quick now.
 
Acesneights1 said:
The quality of distillates in general have gone down the crapper across the board. even heating oil i sell is dirty looking compared to five years ago. IMHO They are not refining it as good.
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Kenny I'm running Yankee fuel since March now, as I said before changed injectors here in NY in May and mpg went up running same/very similar fuel as you & Stacks I would imagine
 
I normally run Hess fuel and get the most consistent mileage, low 16's to mid 17's with my city/hwy driving. All highway is in the low 20's.

There's a few Mobil stations around me that carry diesel and my mileage always drops when I run their fuel for some reason. I think it has to do with the fact that the Hess does a lot more business and goes through a lot of fuel which is always getting refreshed.

I noticed that the Mobil fuel smells differently (almost like paint thinner) than the Hess fuel when filling the tank.
 
I have been running Shell lately with good success. I have also used a lot of Hess fuel in the past with great success. The Shell station is much closer to me and on my route home.

I am at a loss Joe. I am not sure why the terrible mileage. Many members have stated that the larger tires cost you a loss in fuel mileage. I got my best mileage with the stock tires. At about 50K, I went with 265's and noticed a little loss going from 22-23 down to about 20. I used my tuner to change tire size, run a mild tune, use either Stanadyne or Power Service and 2 stroke in EVERY tank, and drive the same way every day. I have to say that I do not beat on my truck. I drive like an old man. With that being said, I don't know what else it could be.
 
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I try to stick with Chevron's diesel in my truck. This last tank I had I ran quite a bit on the highway (mind you highway is open here, but lots of hills and curves) and the DIC said 18.3, but I hand calced it at 19.5. I reset both the trip and the Avg. Economy counter when I filled up. This tank I did the same but added some Power Service, will repeat calculations and post results.
 
83GMCK2500 said:
I try to stick with Chevron's diesel in my truck. This last tank I had I ran quite a bit on the highway (mind you highway is open here, but lots of hills and curves) and the DIC said 18.3, but I hand calced it at 19.5. I reset both the trip and the Avg. Economy counter when I filled up. This tank I did the same but added some Power Service, will repeat calculations and post results.
Click to expand...

On a bright note, I have seen almost a 4mpg increase on the jeep after swapping the axles. Definitely not working near as hard climbing the hills now. :thumbsup:
 
stacks04 said:
I last week I did about 70 miles of towing, and about 200 city/highway and thats about it on a tank of fuel. 23 gallons to be exact. By my calculations that is about 12 mpg. What in the hell do think is going on? I imagine i should be doing alot better. My trip down to Virgina beach last summer also only got about 15. That was all highway. My ipc speedo was broken, but now isnt and i got around to calculating things and some past trips via mileage numbers off of google maps and this is what I am coming up with. Any thoughts on this? My trip to myrtle towing my trailer is going to be costly with that kinda of mileage.
Click to expand...

I was getting that for a while too... found out if I back it down from 120 to 80mph, I could climb to ~15mpg. Usually don't see more than that since my truck is always around 8500lbs with 100lbs of wheel/tire on each corner. My DIC tells me I'm getting 22.1 though ):h .... Those POS never work right.

Not sure where else you can look. I know I get better mpg running CA diesel than I do NV diesel :confused: ..... Same in AZ. Nevada must have some crappy #2 I guess.
 
Well I reflashed back to stock with the tech 2, I finally did the update for the lbz filter housing from gm, not just adjusting the table. I did the lbz filter right around the time this started happening along with a few other things, so its a matter of ruling things out. I am curious if gm changed things that efi live doesnt see so I the update and will tune off that base tune. Just love the cel with egr codes again though:)
 
I used to run either Mobil or sunoco fuel and thought my milage was decent. Recently I switched to shell and saw a significant improvement. Try changing to a different supplier and see if that helps.
 
I will try that. I have got 60 cents off a gallon for sunoco from price chopper so i will use it but once that is gone will try the shell. I will do anything right now to get me back to the high teens.
 
Well, I am back and have tabulated my data from the trip. I would run around 200 miles then stop for fuel. (I had a big scare last trip south last year when I had the low fuel warning come on and hit traffic almost the exact same time.) wanted to avoid that this year. At 200 miles I was at about 1/4 tank. Each refill would yield about 17 gallons, for around 12 mpg. My trailer is 18 ft enclosed cargo empty weighing 3500# and as I towed approx 6000# total. I was not shocked with that. I used every fuel on the east coast, shell, exxon, mobil, flying j, some odd no name hindu joint in nc, and the scotchman fuel. Mostly highway driving 70 mph.

The surprising thing was when i got back and unloaded. I fuel up and and currently getting 13 mpg. I guess the days of 18-20 are gone for some reason for me. My buddys truck, same tunes as i run is still getting the value from the extra cost of the duramax though.
 
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