• If you currently own, previously owned or want to own an Avalanche, we welcome you to become a member today. Membership is FREE, register now!

Gas mileage!

Cauds

Full Member
Joined
Apr 15, 2021
Messages
23
Any ideas on improving gas mileage. After I put a leveling kit on her and 33x12.5x17’s she dropped to 9-10 mpg. I’d love to get a couple mpgs back! I’ve had the cats deleted and retuned the computer to bypass the torque management system. Runs great, love the take off power!
 
drive a smaller vehicle... LOL

No real way to improve mpg other then your driving style...

lso lower the front end back down and smaller tires will help greatly - Less wind resistance and less mass to get rolling.

Undo your power tune and put it back to stock... is best way to start to get more MPG
 
I got same exact MPG with stock tune. I’m just trying to do what I can to keep her in good shape. With 237k miles and 19yo she’s got a few parts wearing out. I’m a surveyor and she was my work truck for 10 years.
 
There is a mountain of threads on improving gas mileage on this site, a little word search should show you some ideas.
The AV is a poor choice for gas economy due to it's weight and lack of aerodynamics. Putting lot's of weight onto it with bigger rims and tires (not to mention ading large bumpers and winches etc.) as well as lifting an AV can lower gas mileage.
Best things you can do is to give the AV good maintenance and drive it like an old geezer with slow take offs and stops. Try to stay on highway at a steady moderate speed as well.
 
I get 16.9mpg and that's with 22's on 305/40R22, if I'm mashing on the gas @ every stoplight then it's 9-10mpg.
 
The only other way I know to possibly gain a couple of MPGs is to help the engine breathe easier, if you haven't already. It is pretty easy to replace the restrictive air intake system with an aftermarket K&N or Airaid unit. Expect a little more noise. Sounds like you already attended to the exhaust system. I didn't touch the cats but replaced the OEM muffler with a Flowmaster. I have also found that using the cruise control helps.
 
The only other way I know to possibly gain a couple of MPGs is to help the engine breathe easier, if you haven't already. It is pretty easy to replace the restrictive air intake system with an aftermarket K&N or Airaid unit. Expect a little more noise. Sounds like you already attended to the exhaust system. I didn't touch the cats but replaced the OEM muffler with a Flowmaster. I have also found that using the cruise control helps.
It’s the craziest thing. If I drive normal during the week, just to work and back and maybe around town a little I get the same mileage as I do when I’m cruising down the interstate with the cruise control on. I checked my mileage Memorial Day weekend after pulling my camper with tow/haul on to the lake and back using up 3/4 of a tank. I got 2 mpg better than normal! I guess I’m gonna have to keep my tow/haul on!
 
My '04 was at 12.9 mpg when I bought in April. It was a qt short of oil so I added Lucas Oil Stabilizer. I've used it on all my past vehicles. I slowly watched my mileage climb up to 14.7 today.
Another thing I am going to do soon is a Seafoam cleaning. Pour a bottle in the tank and a spray bottle in the intake. Look up some "How to Seafoam my Chevy" videos. Another way is in the vacuum line for the brake booster.
I would change my fuel filter after cleaning. A lot of tarnish will clean out of the gas tank.
I also had a wheel alignment which might help
 
The three biggest boosts to my mileage were cruise control, a couple tanks of gas treated with injector cleaner, and tire pressure/tire type.

I was surprised at just how much better mileage I can get setting my cruise control and leaving it alone. People around here drive like morons. 85mph in the left lane, 60mph in the right. I get better mileage sticking it to 75/80 mph and doing short bursts to mesh with traffic to pass than I would driving a lower speed and having to constantly alter my speed to mesh with traffic or recover after needing to slow down behind slow traffic. Im not too thrilled about it, i would get a bit better mileage going 70 the whole way if i could stick it on cruise control, but the gas math favors the ability to do constant speed. I try to let it coast where I can, this thing doesn't slow down much unless you make it.

Fuel injector additive can work depending on how dirty your engine is. It can potentially give significant fuel savings off the bat if your engine has never had it done. In my case, it was about a 0.4 mpg increase after two tanks (~80 gallons) of fuel mixed with amsoil PI, but techron, seafoam, and lucas injector cleaners work on the same principals. Like 2smokin' suggested, cleaning the intake out more directly with seafoam can speed this up significantly if done right. It will help rid thei ntake of carbon deposits around the valves.

lastly, your tire size, pressure, and tread type all play a role in fuel economy. The dealer underinflated my new set of snow tires. (40 psi). I was getting roughly 0.5mpg less compared to my A/T tires that came with the truck. After going back to have it corrected, I saw roughly a 1.2 mpg increase overall. (60-80psi is typical, I told them to go 80 for tire rotation purposes, my compressor doesn't do above 45 well at this size. ) My snow tires, which are blizzak LT's are highway profiled. Despite being softer, they have less rolling resistance in the winter than your typical blocky all terrain tires and therefore can increase MPG. Personally, as someone that doesn't go off the road much, ill be going to a standard highway all season once these a/t's are done with. God those blizzaks were so much quieter. Keep in mind, when a 2500 is getting ~10-11 mpg, every additional mpg is a substantial increase. Right now, I'm averaging 11.0 mpg (calculated), and my best in the summer thus far has been 12.2 (calculated) and my best in winter was just shy of 13mpg. I do 90% highway driving.

Beyond this, the only possible increases in mpg is to make the truck more efficient. You would need to look a second gen for the 6 speed and notorious VVT along with the streamlined form. In general, doing the opposite of whatever you'd do for offroading is basically the goal for making vehicles more efficient. Lower stance, lighter weight components, lower gear ratios, eliminating the leech and weight of the 4wd system, thinner highway tires, reduce displacement in favor of better power-to-weight ratio choices, ect. And realistically, most of those things are a must the way they are for most owners.
 
Just got a good highway check since last Saturday in my 2004 Z71. Rolling terrain, entirely on I-80 from South Bend Indiana to Omaha Nebraska and back. 80mph with A/C on. Going there = 18.4 ave. Coming back = 18.6 ave. Such a comfy vehicle to drive!

15mpg at home combined city/secondary country roads between the town where I live and the town where I work. I have a pretty light foot unless trying to make time.

Now, if I could just get it to stop setting periodic knock sensor codes. Already replaced both knock sensors with GM parts. Guess I need to start looking at things like grounds.
 
Last edited:
Dang you guys are fast lol. My daily commute is 30 minutes long, mostly at 80 km/h (50 mph). At 80 mph they can impound the truck. Or $368 ticket.
If you have conversion try looking at metric for fun. I'm currently at 14.7 mpg = 15.9 litres/100km . The lower the number, the better. I was using 17 litres.
Btw gas prices here are at $1.43/litre can. or $4.39/g u.s.
 
Dang you guys are fast lol. My daily commute is 30 minutes long, mostly at 80 km/h (50 mph). At 80 mph they can impound the truck. Or $368 ticket.
If you have conversion try looking at metric for fun. I'm currently at 14.7 mpg = 15.9 litres/100km . The lower the number, the better. I was using 17 litres.
Btw gas prices here are at $1.43/litre can. or $4.39/g u.s.
See, when the vast majority of traffic on the road is doing 80-90mph, it's just kinda what you end up doing.

The police don't bother enforcing the speed limit, it causes too much congestion on a two lane major highway and as a result, people don't care.


They e had tons of construction going on lately and they keep talking on pitiful attempts to slow people down. Rumble strips in the lane, flashing lights anywhere, radar speed display signs every couple miles. Nothing works.

So sadly, driving well over the speed limit is just about the only way to drive safely. If you don't get over when the getting is good, you'll get stuck behind that semi for a good 4 miles before there's finally a gap that you can slide over I to and speed up again.

Its pitiful really, because as bad as that is, during non peak rushour times it's totally normal tk have a couple 100mph guys fly by. But that's what happens when you have no police.
 
Dang you guys are fast lol.

The speed limit on rural Interstate highways around here is 75 MPH.

Folks around here take any speed limit sign as a suggestion for the "minimum" speed to be driven.

:ROFLMAO:
 
Except that one guy that sees the minimum speed limit sign and says "challenge accepted" and is doing 45 on the freeway and causing accidents when people try to avoid them. When semi trucks are passing you regularly, it's time to take be backroads.

When a particular coworker leaves before I can tell, there tends to be a lot more traffic on the way home because he drives just barely better than this.
 
Last edited:
Except that one guy that sees the minimum speed limit sign and says "challenge accepted" and is doing 45 on the freeway and causing accidents when people try to avoid them. When semi trucks are passing you regularly, it's time to take be backroads.

When a particular coworker leaves before I can, there tends to be a lot more traffic on the way home because he drives just barely better than this.

I have been known to say that once I was signed up for my AARP membership, one of the requirements was to always drive in the leftmost lane, 5 clicks under the speed limit and with my left turn signal on until I finally reach my exit.

It's not like I WANT to, but rules is rules.

:ROFLMAO:
 
What these guys are saying is definitely true. I-80 speed limit is 70. If I set cruise at 76-77 and drive in the left lane, I am always having to pull to the right and let people around me - then I get stuck at much slower speed (typically behind trucks pulling up the rolling hills of Iowa/Illinois) until traffic clears in the left lane. However, if I set it at 79-80, then only a few people want to pass - so I assume that is the normal speed for traffic. Probably would be a lot different without the trucks in the right lane that can't hold a steady speed or on flat terrain. So it's either drive 80 mph in the left lane or constantly speed up and slow down when forced into the right lane.

Funny thing but my Avalanche seems to get same mileage at 80 as it does at 60. It doesn't make sense but seems to be true. The thing flat out cruises - feels like it could even do 90 all day. As it is, I went 600 miles there and 600 miles back at 80. A real land yacht!

Here's a video I took around Davenport, Iowa on I-80 a few years ago. Focus of the video was the tiny little car that just had passed me at 85+mph and then slowed down. I know his speed because my cruise was set to 82 and I moved over to right to let him pass. To me it was hilarious.

 
Last edited:
Okay, i take it back, the people who pass you and refuse to use cruise control are the absolute worst. (its a whole 'nother things to put around in the slow lane) They'll go 70 +/-10 mph making it impossible just to sit back and drive. They get over t let you pass, only to decide to speed up when they're behind you and impatiently drive around. You get to play leap frog with them in traffic.

silver medal to morons that have the urge to speed like crazy, but then dont feel safe going around semi trucks and slow down to like 65 mph every time they come up to one in the left lane, only to speed off at 85 afterwards.

Both of these people quite literally make things really stressful to drive with daily and inspire those morons to whip over into the right lane and try to cut people off farther up because their house is apparently on fire.
 
Last edited:
Heck, I don't care if somebody is driving 100 mph as long as they're not zigging and zagging in traffic and most importantly, they aren't texting while driving. Those are the yahoos I seem to always play dodge 'em with and also whose speed seemed to randomly change 20 mph for no reason.
 
My '04 was at 12.9 mpg when I bought in April. It was a qt short of oil so I added Lucas Oil Stabilizer. I've used it on all my past vehicles. I slowly watched my mileage climb up to 14.7 today.
Another thing I am going to do soon is a Seafoam cleaning. Pour a bottle in the tank and a spray bottle in the intake. Look up some "How to Seafoam my Chevy" videos. Another way is in the vacuum line for the brake booster.
I would change my fuel filter after cleaning. A lot of tarnish will clean out of the gas tank.
I also had a wheel alignment which might help
So I did perform a Seafoam cleaning about three weeks ago. That would also be 3 tanks of gas. My MPG at the time was 14.7, and is now 15.1 mpg. Quite happy with her performance right now. I'm sure there is still many things to upgrade and improve on this.
Think I'll change the oil today as a reward. There has been 0 loss of oil in 3 months use. I have put on about 4000 miles.
Also changed the coolant 2 weeks ago
 
Last edited:
Oil change was a great call. Not a day too soon. Was draining pretty dark.
Put in some cheap conventional 5-30, was 50% off i'll change it again before winter
 
Oil change was a great call. Not a day too soon. Was draining pretty dark.
Put in some cheap conventional 5-30, was 50% off i'll change it again before winter
Yeah, it's always best to do a seafoam treatment right before you change your oil. (Few hundred miles or so) especially when using it directly in the oil itself.

All of those deposits have to go somewhere. If not out the exhaust, it's in your oil.
 
I got 19.8 mpg highway on my June vacation trip With my 2005 Z66, typically cruising at 70 mph. Loaded down with luggage, beach umbrellas, beach chairs, coolers, bottled water, non perishable groceries etc. With a curb weight of 5,438 lbs. Loaded I was grossing well over 6,000 lbs. I knew I wasn’t buying a Prius when I bought the truck used almost 8 years ago so I’ve always been OK with the fuel mileage, like it’s “the nature of the beast”! I’m actually pleased it can get almost 20 mpg under those conditions, also not too bad for a 3 ton brick! As usual, YMMV…;)
 
Daughter graduated from college this spring! Went to pick her up and move her back home. 600+/- mile round trip. 11.87mpg there at 80mph. Rented U-Haul trailer when we got there and got 10.37mpg on return trip at 65-70mph. Did a B12 Chemtool treatment on the fuel and a Seafoam treatment in crank case. Will change oil in a couple hundred miles. Hopefully I’ll be able to report a little better fuel consumption in the near future.
 
Back
Top