I am fairly new to this forum. I have a 2001 GMC 8.1 EC/LB 2500, 3.73's, 4x4, SLE. It has 75K miles, is well maintained and runs strong. No oil usage problems. I just bought a 5th wheel toy hauler/camper, 10-11K loaded. I also bought a goose neck enclosed trailer about 9k loaded. My truck has no problems hauling these trailers 75 mph, just wont pass many gas stations at that speed, however at 65, I get 8 to 8.5 loaded. I am getting ready to use the truck as it was intended...Towing my way around America, until I figure out where I want to retire. Was going to buy a diesel, but with diesel 30% higher, it doesn't make sense.... My truck has a hypertech tuner. Monroe Shocks and Foose Wheels. I run 265/75/16 Bridgestone T/A's, Load Range D, 65 PSI. I am thinking I should go to 245/75/16's Load Range E, 80 PSI, in a ribbed tire to help mileage. Any tune modifications? Spark plugs etc? Air filter? How about exaust? Dual exhaust? Catback? Do any of these things really help mileage?? Thanks.

I would like to see the replies to the OP too!

There's really not much you can do to net a significant MPG benefit other then putting your right foot on a diet.

I netted about 1 MPG gain going with a Wait4me tune, spark plug mod, opened airbox and 180 degree thermostat.

I average 12.5 MPG but it's mostly empty and mostly country driving. (very little city or freeway).

There's really not much you can do to net a significant MPG benefit other then putting your right foot on a diet.

I netted about 1 MPG gain going with a Wait4me tune, spark plug mod, opened airbox and 180 degree thermostat.

I average 12.5 MPG but it's mostly empty and mostly country driving. (very little city or freeway).

man 12.5???

Hell Im happy as hell when I see anything above 8. Dont start wasting your money on trying to increase mileage. Its not going to happen. Best thing you can do is get ahold of an EFI LIVE tuner suck as Nick at duramaxtuner.com and have them write you a tune. Will increase different parameters better than Hypertech and can retune it anytime you want with a laptop. Might pick up a mile or two but dont hold your breath. Big motor=Lots gas. :D

man 12.5???

Yea, but the 12.5 comes primarily from rural roads doing about the speed limit. It's the stop and go city driving that can really kill MPG.

I can almost sqeak out 14 on a flat freeway doing around 70. However it drops pretty quickly >70 mph.

I bet if I did primarily city driving it would drop below 10 pretty quickly.

I bet some headers and high flow cats would do wonders. And at least a k&n drop in filter. And definatly somthin better than a hypertech. My dads 6.0 vortec got 13 frwy stock, 14.2 with the hypertech, 17.5 when i tuned it with EfiLive.

i gained 2mpg with the addition of a straight exhaust on my 1500 5.3. even with a 4.10 rear end i was returning around 21mpg..... but i certainly couldnt tow anywhere near the 8.1, i am willing to bet i could pull harder than a stock 6.0 though and return better mileage. i kinda miss that truck...

exhaust and a tune

exhaust and a tune


^^^^^ like he said, If you got the cash to spend you'll gain alittle bit. I think...I hope...

I just tuned mine with efi live but have not checked the mileage yet....but I have been checking my right foot out on the gas pedal.:D

yup, intake or even a aftermarket filter is a waste. stick with delco or amsoil nanofiber

I have a custom tune also and get 12.5-14mpg on flat ground.I have 3:73 gears and 285 tires and run 65-70mph on average daily.I run cruise 90% of the time. I was told the exhaust won't gain much.All I have is a K&N filter and a nelson tune on 91 octane.

I have never seen any real data where exhaust had done much for these trucks. The run pretty large exhaust anyway. I put true duals with an H pipe, and I don't get one bit better mileage than I did before. Can't tell you the power is any better either. Just sounds much better. I would spend my money on a good tune and not worry so much about the exhaust. I get 13 with a 6 speed alli

If you get 10 MPG and you do something that will increase your fuel economy by 1 MPG to 11, that represents a whopping 10% increase. And if the mods that you do increase your MPG to 12, that is a huge 20% economy boost. I think that given: Everything is stock and all the sensors work correctly, you may approach this magical 20% increase by spending $10 on a 180* t-stat...this single, simple mod reaps tremendous benefits by keeping the BB out of heat-induced spark retard and makes the whole powertrain run, on average, 15* cooler...taken one step further, getting cold, outside air to the OE intake creates another plus--the PCM will retard the spark tables when it "sees" 86* F. inside the air cleaner tubing run...as posted above, the dry paper (OE-style) air filter element works best. These BBs will misfire the plugs at + 3200 RPMs and WILL NOT set a SES light.
Because any spark plug misfire causes a reduction of power and economy, gapping at 40/45 thou. cures this..the hi-speed mis-fire is something that cannot be "pro-tune-d" out of there, it remains. Only by narrowing the gap can it be lessened..with the gap mod, throttle response is sharper, more snappy, and cold starts happen scary fast....

I remember the old 454's were lucky to get 5mpg at any given time.

Count you blessings :D

I have an 02 8.1/ally w/ airaid cold air intake (wouldn't do that again, just the drop in filter) and 245 toyo open country a/t's:D. The truck was UNDRIVABLE in rain or snow with the o/e firestone ribs, so keeping them wasn't an option, and I would strongly advise against it, unless you want to be the sideways drift king of your neigborhood! I get 8.5 city/ 12 highway empty.:eek:

Thanks for all the good info. I purchased Bousch plugs, with 4 electrodes that do not require a gap. My mechanic reccommends against them. What is a good plug to buy to gap at either 45 or 55? I will run a cooler thermostat as reccommended. Go back to stock air filter. I found a good deal on a catback magnaflow exhaust system and try that. My muffler is leaking anyhow...

2001 GMC 4x4 2500 8.1 ec/lb.:o:

I remember the old 454's were lucky to get 5mpg at any given time.

Count you blessings :D

I had the 7.4 Vortec in my last Silverado, installed intake, headers, hypertech and true dual 3" exhaust and it really didn't do to much. I typically got 9-10 no matter what. Loaded or dry........

Anyone have any experiance with an Aero Turbine 3030xl muffler w/ resonator? I wonder how loud that would be w/ 3" tubing?:)

Thanks for all the good info. I purchased Bousch plugs, with 4 electrodes that do not require a gap. My mechanic reccommends against them. What is a good plug to buy to gap at either 45 or 55? I will run a cooler thermostat as reccommended. Go back to stock air filter. I found a good deal on a catback magnaflow exhaust system and try that. My muffler is leaking anyhow...

2001 GMC 4x4 2500 8.1 ec/lb.:o:

WHATEVER you do DO NOT get those 4 prong plugs! They will NOT work AT ALL. Been there done that. Get the ones that are recommended in the spark plug post. Got em myself.... not sure if I could tell diffrence but.....

Might be a silly question, but would a Supercharger help MPG's on this motor?

I had the 7.4 Vortec in my last Silverado, installed intake, headers, hypertech and true dual 3" exhaust and it really didn't do to much. I typically got 9-10 no matter what. Loaded or dry........

I'm referring to mid '80s era 454. 2 20 gallon tanks, I swear you could literally watch the gas needle move as I went down the highway.

I'm referring to mid '80s era 454. 2 20 gallon tanks, I swear you could literally watch the gas needle move as I went down the highway.

LOL, I've heard that about the classics.

I'm referring to mid '80s era 454. 2 20 gallon tanks, I swear you could literally watch the gas needle move as I went down the highway.

I hear that, when I was just a little guy,my dad bought a new 1976 C30 3+3 camper special dually with a 454/TH400 and i think it was 4.11 gearing. With the 11ft camper on the highway,you could literally watch the gas needle move from F to empty in each tank as you drove.

Can't find the post on spark plugs. I talked to the folks down at Advanced Autos, and the have some irridium plugs I think Denso that come gapped at .40. So I may pick them up. I saw where people like the Napa Blue Max plug wires, so I guess I will swing over and get some of those as well. A cloth filter. Then start checking in to live tunes. I already have XM, don't know how live tunes improves mileage/performance. I have noticed I drive faster when a favorite old rock song comes on, but then my mileage goes down???? Ridin' the Storm OUT!.... Keep your eyes on the road, your hands upon the wheel! Those songs just aren't the same in a diesel.

2001 GMC 4x4 8.1 EC/LB Hypertech, Foose Wheels, Monoe Shock, XM, TomTom. 265/75/16 Bidgestone At's

Diesel Fuel is .50 more than Reg on the average. I did all of the math of the operating cost of a diesel over gas, including longevity of the motor, filter and oil, etc....In the long run, a diesel is still cheaper with the gain in mpg's and just the simple joy of pulling with a diesel vs. a gas.

Diesel Fuel is .50 more than Reg on the average. I did all of the math of the operating cost of a diesel over gas, including longevity of the motor, filter and oil, etc....In the long run, a diesel is still cheaper with the gain in mpg's and just the simple joy of pulling with a diesel vs. a gas.


Maybe in Ca diesel is .50 higher, in the N.E. ,its been .50 higher in the summer,and 1.00 higher in the winter,and about .75 higher spring and fall.A lot of ppl heat there homes here with fuel oil which is just tax free #2 diesel,so the temps here drive prices alot.

Diesel Fuel is .50 more than Reg on the average. I did all of the math of the operating cost of a diesel over gas, including longevity of the motor, filter and oil, etc....In the long run, a diesel is still cheaper with the gain in mpg's and just the simple joy of pulling with a diesel vs. a gas.

x2

I have noticed I drive faster when a favorite old rock song comes on, but then my mileage goes down???? Ridin' the Storm OUT!.... Keep your eyes on the road, your hands upon the wheel! Those songs just aren't the same in a diesel

:agreed::HiHi::beerchug: I hear that buddy.

Diesel Fuel is .50 more than Reg on the average. I did all of the math of the operating cost of a diesel over gas, including longevity of the motor, filter and oil, etc....In the long run, a diesel is still cheaper with the gain in mpg's and just the simple joy of pulling with a diesel vs. a gas.
Have you done the math using fuel economy numbers that many people are seeing from the NBS trucks? Also, is longevity really an issue anymore? I have seen many Chevy small block gasoline truck motors go over 300K miles with simple maintenance. Now honestly, how many people are going to keep their truck for hundreds of thousands of miles? I have done the math too and for me the diesel would have turned out cheaper in the long run, but that long run is about 10 years or more at current fuel prices. Where I live diesel is currently just about $.90 - $1.00 more per gallon than regular gasoline.

There's definitly no dispute that dmax gets better mpg than 8.1. As to how much better that seems to sure depend on what year dmax you're talking about and who gives the reports. I see reports here from 9 all the way up to mid 20's.

BTW here's something some of you dmax owners could do. Keep a log book of gas (excuse me...fuel :D ) fillups over an entire year and then report back. I'd like to see what yearly average you get. I posted mine here starting the day I drove it off the lot.

Also no dispute about extra cost of dmax.

All other calculations depend entirely on how many miles per year you drive. Me personally I put about 10,000 a year. It would take a looooonnnng time to offset the cost of a diesel. These gas engines nowadays can easily go 200k and beyond without any teardown repairs. For me that's going to be 20 years. I can guarentee that in 20 years it's not the engine that will be nickle and diming me for repairs. I'm sure by then I'll be wanting a newer truck anyway.

The 8.1 has all the power I need, I never have to worry about fuel gelling, and quite frankly I hate the smell of diesel fuel.

The biggest trick to running a big block is keep a choke hold on your right foot.

Have you done the math using fuel economy numbers that many people are seeing from the NBS trucks? Also, is longevity really an issue anymore? I have seen many Chevy small block gasoline truck motors go over 300K miles with simple maintenance. Now honestly, how many people are going to keep their truck for hundreds of thousands of miles? I have done the math too and for me the diesel would have turned out cheaper in the long run, but that long run is about 10 years or more at current fuel prices. Where I live diesel is currently just about $.90 - $1.00 more per gallon than regular gasoline.

Uh.........ok.

I think the gassers and diesels each have their own merits. Hard to buy any new diesel with regen, as there are still too many problems. Gotta give it a year or two. Gotta see where the price of diesel goes. I have been driving a VW TDI for years. Never seen these kinda diesel prices. 25 to 30 percent more. Let's face it when those diesels go out of warranty, and things break, it gets real expensive. So gonna make my gasser the best it can be without dumping too much money in it, and drive it for a another year or two. I can put a lot gas in it for the taxes on a new truck. I only pull up to 11k lbs, but it is somewhat of a sail. When I get in a good wind. I wish I had a diesel. Otherwise i have no problems hauling at 65 MPH, 8.5 mileage, and rarely kicks down, as long as it's my foot, not the cruise. Was hauling 6k enclosed car trailer yesterday through the hills of Virginia backroads at 55 mph. Still got over 10. Any suggestions on sparkplugs, muffler?

2001 GMC EC/LB, 8.1, Foose, Monroe, XM, TomTom. Hypertech.

ggggrowl is cool til mile 50, then I like the quiet all day power of gas.

I test drove diesels and they always feel like slugs in all around driving. I agree they're great on the open freeway but for me that's <25% of my driving. They also do well at high altitudes but that's <1% of my driving. I test drove several 8.1's and couldn't believe the spirited feel compared to diesels. I bought one of the last classic Sierras with 8.1 and love it to death. It's like a Corvette in the shape of a truck.

The other beauty of the 8.1 is that it's old fashioned big block technology that GM's been making for at least 30+ years. Repairs are simple. If a diesel breaks out of warranty your looking at increments of $1k!!

I'm averaging 12.5 MPG. The LMM crowd is bitching about 15 MPG and they're paying a $1.00/gallon premium over gas and payed $8k premium to get the diesel. I fail to see the advantage unless you're doing lots of heavy towing.

My dealer told me diesel resales are poor these days.

I like the new body style Sierra, (hate the Silverado), but wish GM would bring back the 8.1 given the changes in fuel economics these days. 6.0 isn't enough engine in a HD truck. Maybe it could be with a blower.

I test drove diesels and they always feel like slugs in all around driving. Yeah, right...... I agree they're great on the open freeway but for me that's <25% of my driving. They also do well at high altitudes but that's <1% of my driving. I test drove several 8.1's and couldn't believe the spirited feel compared to diesels. I bought one of the last classic Sierras with 8.1 and love it to death. It's like a Corvette in the shape of a truck.

The other beauty of the 8.1 is that it's old fashioned big block technology that GM's been making for at least 30+ years. Repairs are simple. If a diesel breaks out of warranty your looking at increments of $1k!!

I'm averaging 12.5 MPG. The LMM crowd is bitching about 15 MPG and they're paying a $1.00/gallon premium over gas and payed $8k premium to get the diesel. I fail to see the advantage unless you're doing lots of heavy towing.

My dealer told me diesel resales are poor these days.:rotflmao::rotflmao:I am from the government and I am here to help you.:D

I like the new body style Sierra, (hate the Silverado), but wish GM would bring back the 8.1 given the changes in fuel economics these days. 6.0 isn't enough engine in a HD truck. Maybe it could be with a blower.
Uh..........ok

Uh.........ok.
Sorry if this is too complicated for you to understand.

:lol2: Nope, not hard at all.:D That was the.....oh, never mind.

I test drove diesels and they always feel like slugs in all around driving. I agree they're great on the open freeway but for me that's <25% of my driving. They also do well at high altitudes but that's <1% of my driving. I test drove several 8.1's and couldn't believe the spirited feel compared to diesels. I bought one of the last classic Sierras with 8.1 and love it to death. It's like a Corvette in the shape of a truck.

The other beauty of the 8.1 is that it's old fashioned big block technology that GM's been making for at least 30+ years. Repairs are simple. If a diesel breaks out of warranty your looking at increments of $1k!!

I'm averaging 12.5 MPG. The LMM crowd is bitching about 15 MPG and they're paying a $1.00/gallon premium over gas and payed $8k premium to get the diesel. I fail to see the advantage unless you're doing lots of heavy towing.

My dealer told me diesel resales are poor these days.

I like the new body style Sierra, (hate the Silverado), but wish GM would bring back the 8.1 given the changes in fuel economics these days. 6.0 isn't enough engine in a HD truck. Maybe it could be with a blower.

Sorry if this is too complicated for you to understand.


8.1L has more bottom end than a diesel????? You obviously have never driven one then.... I have driven both. Not only will the Diesel have superior mileage it will pull at speed up and down grades all day long... as far as repairs I don't know, never had any of my trucks breakdown...

There's definitly no dispute that dmax gets better mpg than 8.1. As to how much better that seems to sure depend on what year dmax you're talking about and who gives the reports. I see reports here from 9 all the way up to mid 20's.

BTW here's something some of you dmax owners could do. Keep a log book of gas (excuse me...fuel :D ) fillups over an entire year and then report back. I'd like to see what yearly average you get. I posted mine here starting the day I drove it off the lot.

Also no dispute about extra cost of dmax.

All other calculations depend entirely on how many miles per year you drive. Me personally I put about 10,000 a year. It would take a looooonnnng time to offset the cost of a diesel. These gas engines nowadays can easily go 200k and beyond without any teardown repairs. For me that's going to be 20 years. I can guarentee that in 20 years it's not the engine that will be nickle and diming me for repairs. I'm sure by then I'll be wanting a newer truck anyway.

The 8.1 has all the power I need, I never have to worry about fuel gelling, and quite frankly I hate the smell of diesel fuel.

The biggest trick to running a big block is keep a choke hold on your right foot.

Will 2 years worth of fuel data work for you?? I've owned it my LB7 for 2 years and have driven just under 30k miles with it and am anal about keeping fuel records.

It's costing me $.22/mile for fuel and $.28/mile for fuel and maintenance.

I don't have the spreadsheet in front of me but my best tank was around 19.5mpg and the worst was between 6.5 - 7mpg. The low one was pulling a loaded gn trailer into a 30+ mph headwind at 70mph. Probably should have slowed down on that one.

Here is an example of how more mpg does not always mean you are saving money. Where I live regular gasoline is about $2.999/gallon and diesel is around $3.979/gallon. For this example we will say gasoline is $3/gallon and diesel is $4/gallon. On the same drive that my brother's LLY gets about 18mpg on I was getting about 14mpg with my NBS gasser, so with in 300 miles my brother would spend about $66.68 on diesel and I would spend about $64.29 on regular gasoline. Most people are claiming about 16+mpg on the highway with the NBS HD gasser, so lets just say my brother's LLY gets about 21mpg and I get about 16mpg on the highway. At those highway figures, my brother would spend about $76.20 on diesel and I would spend about $75 on regular gasoline in 400 miles. From what I hear, the new LMM is not getting as good fuel economy as the previous Dmax engines also. Obviously, these figures may not relate to some of you for many people experience different results depending on your type of driving and truck.

8.1L has more bottom end than a diesel????? You obviously have never driven one then.... I have driven both. Not only will the Diesel have superior mileage it will pull at speed up and down grades all day long... as far as repairs I don't know, never had any of my trucks breakdown...

I agree that the diesel will out pull an 8.1 and get better MPG. My point is that for all around driving the 8.1 is much more fun to drive - they just feel much more spirited.

I agree with Davefr. I have owned two 8.1's 2001, and 2006, and two Dmaxs, lb7 and lly. No doubt for straight pulling power, a diesel is the winner. For quickness off the line and all around fun factor, I have to say the 8.1 is much better. I pulled the same trailer with all these trucks, and the lly pulled a load the best, but the 8.1 does a great job as well for what I use it for. If you turboed an 8.1, you would see it pull loads at speed up hills as well. It's the turbo that makes a diesel. Did any of you ever drive a non turbo diesel? Talk about a pig, they were a big time pig.
As far as complexity goes, there is no comparison. The dmax are way more complicated than gassers. There is much more going on under there to get that kind of power out of them. Yes, they are reliable, but if something does go arwy, it is big bucks to fix if the warranty is out.
So let's shoot this dead horse for the last time, and agree that some people like gas and some like diesels, and get back to what this post was about in the first place and that is "Best 8.1 Improvements" . Okay?

8.1L has more bottom end than a diesel????? You obviously have never driven one then.... I have driven both. Not only will the Diesel have superior mileage it will pull at speed up and down grades all day long... as far as repairs I don't know, never had any of my trucks breakdown...
I'm going to have to disagree with you there Justin. My dad has the 8.1, and I've put several miles on it. The throttle response on it blows my duramax out of the water. Stock motor vs stock motor the 8.1 will lite the tires where my duramax just won't do it. The mileage with the new LBZ or LMM is not that good, with higher diesel to boot. As far as repairs, my dad's 6.0 went 325,000 miles before we retired it to the farm. It probably only had 5 oil changes in that time, with no new plugs or anything.

I'm going to have to disagree with you there Justin. My dad has the 8.1, and I've put several miles on it. The throttle response on it blows my duramax out of the water. Stock motor vs stock motor the 8.1 will lite the tires where my duramax just won't do it. The mileage with the new LBZ or LMM is not that good, with higher diesel to boot. As far as repairs, my dad's 6.0 went 325,000 miles before we retired it to the farm. It probably only had 5 oil changes in that time, with no new plugs or anything.

the 8.1 i drove must have had something wrong with it i guess?:cool:
of course me lb7 will smoke the tires 1,2,3, and part of 4th...... off the line too... but shes modded...

Uh.........ok.

Uh.........ok.

Man, I love this place.:)

The 8.1 has more torque until the diesel gets the turbo lit up which does take a few seconds with a stock truck.At that time a stock LB7 duramax has more torque,not much,but it does have slightly more.The 8.1 has it instantly ,and carries it higher,much higher.It has a livelier feel than a duramax does.The LBZ does have quite a torque advantage over the 8.1 ,you can really feel the LBZ pull,even stock.

Uh.........ok.

that the best u got?

Arguing trucks is like arguing what the best deer rifle and caliber is. A lot of fun, especially after a few beers. What are the best plugs for my 8.1? How do you get the screen out of the airflow sensor? Who to talk to about a live tune? I like my GMC 8.1. I really like when I merge into traffic, and the BMW that was going to pass me can't catch me.:rolleyes:

2001 GMC 2500HD, 8.1, Hypertech, 4x4.

Arguing trucks is like arguing what the best deer rifle and caliber is. A lot of fun, especially after a few beers. What are the best plugs for my 8.1? How do you get the screen out of the airflow sensor? Who to talk to about a live tune? I like my GMC 8.1. I really like when I merge into traffic, and the BMW that was going to pass me can't catch me.:rolleyes:

2001 GMC 2500HD, 8.1, Hypertech, 4x4.

Hell yeah....I hate BMW's.:)

I agree that the diesel will out pull an 8.1 and get better MPG. My point is that for all around driving the 8.1 is much more fun to drive - they just feel much more spirited.
Din, ding ,ding, we have a winner.
I have one of each. One is for work, one is for fun. They each have their place.
The thing is, when I'm "playing around" with the 8.1, I can see the gas guage move. Still fun though.

yeah, I put my truck back to stock last weekend..... its a dog stock.....at least for 3 seconds.....