Huge increase in gas mileage... What could cause this?

[dowsewashere]

I was getting 12-14 city and 14-16 highway. I could fill for 77$ and drive 240 or so miles a week. Then i bought a passat and cut that number to 30+ mpg avg and 30$ a week.

 

[ShadowRejects]

Meh. I dont see how you guys are getting such awesome fuel economy. I have a 1994 5.7 350 3.42's on 35's with a 6" lift and lately I have been very easy on the pedal just to see how far I can get my mileage up, and i still range 160 miles on a good week. I hope when I swap out my gears, that will change and go up.

 

[great white]

Meh. I dont see how you guys are getting such awesome fuel economy. I have a 1994 5.7 350 3.42's on 35's with a 6" lift and lately I have been very easy on the pedal just to see how far I can get my mileage up, and i still range 160 miles on a good week. I hope when I swap out my gears, that will change and go up.

Well, mines a turbo diesel, it's wearing stock sized tires and has no lift. It's also a 4L80E and has 4:10 finals.

It does everything I ask of it and it gets 15-20 mpg.

Even dragging our 8500lb trailer it still gets 13-15 mpg.....

As your truck goes "up", your mileage comes down....

Bigger tires are the worst thing you can do for mpg. You're adding weight int he worst possible area and your mucking up the final ratios that the computer is looking at.


They do "look cool" though.....

 

[SkyHighColorado]

Meh. I dont see how you guys are getting such awesome fuel economy. I have a 1994 5.7 350 3.42's on 35's with a 6" lift and lately I have been very easy on the pedal just to see how far I can get my mileage up, and i still range 160 miles on a good week. I hope when I swap out my gears, that will change and go up.

I have pretty much the same set up as you, but with 4:56 gears ..best I ever got was 368 on the way home from Wyoming so it was kinda down hill and all highway. I usually get between 275-300 here in the mountains.

 

[ShadowRejects]

I have pretty much the same set up as you, but with 4:56 gears ..best I ever got was 368 on the way home from Wyoming so it was kinda down hill and all highway. I usually get between 275-300 here in the mountains.

HOW IS THIS POSSIBLE?! my friends 6'' 2001 ext on 35's gets 300 miles a tank as well. Im praying its all in my gears. Thats awesome to get 368 on a single tank, thats better than my truck when it was stock!

 

[SkyHighColorado]

I think the gears will help a lot! And some good spark plugs. I do have a stage 1 jet chip but I don't think it helps mpg that much.

 

[SAATR]

Gears will help tremendously, as you have a much lower effective gear ratio with tires that size. Physics are still working against you though.

Sent from my XT912 using Tapatalk

 

[1998K1500]

No, that's pretty bad no matter how you slice it.

that's 454 territory at 350 power levels.

If that was a constant number, I would get rid of that pig as soon as I could.

Consider this:

I average 15-16 mpg city. That's right around double the MPG you're quoting.

I spend about $115-130 on a normal fill and that lasts me about 1 month.

so per year is 115x12= $1380

If I were getting half my mpg (your 8 mpg) my annual costs for fuel would be $2760.

Double my costs and I already pay too much annually for fuel as far as I'm concerned.

Yep, that 8 mpg truck would be sooooo gone. I need a truck but 8 mpg is too low, especially from a 350. I've got better things to spend 1300 bucks on than fuel....

I always thought it was bad but I've always been trying to justify it hahah.. I do drive with a heavy foot and very rarely highway (I know, you're getting 15 city only and I am very jealous of that)

It's winter now and naturally my mileage will drop a little but over my next tank or so I'll drive a little more conservatively and see where my number is at.

Assuming it's not my driving (I doubt it could drop it in half...?) Do you have any thoughts of what really could be causing it because getting rid of this truck is not an option for me

EDIT: Just read your other posts here and found out you have a turbo diesel so that explains it but that's still pretty good... thinking back on it I'm not sure when the fuel filter has been replaced, I'd like to replace spark plugs soon, and I have an 02 sensor code, though I know for a fact the 02 sensors are not bad... I'm sure none of that is exactly helping me but could fixing all of that save it that much?

 

[Sampuppy1]

I have a stock 1500, vortec 5.7, 3:73, 265/75@35psi, CAI, dual exh. (Cats only no mufflers), run 5-30 synthetic and 80-90 synthetic gear oil, 25 gallon tank I average between 200-260 per tank to empty. That's 9-10 mpg. Never got better than that. Lowest was 160 but that was lots of skinny pedal. I'm sure a better exhaust, new o2 sensors, MAF, IAC, and tstat would help. But I'm not fuggin with all that right now


Sent from what is likely a government flagged smartphone. Tyler/T-Unit

 

[Kyle97GMC]

I get about 12 city with my heavy ass truck , 5.7, 33s, and 3.73s whether I baby it or drift around every corner