how do i improve mileage on an 8.1? - Chevrolet Forum - Chevy Enthusiasts Forums

how do i improve mileage on an 8.1?

Join Date: Jan 2010
Posts: 18

August 29th, 2010, 7:32 PM   #1  
how do i improve mileage on an 8.1?

i did not get this truck for it's economy but to use it for what it is. but at the same time i found myself driving on the highway alot. i am getting almost 15 MPG now so i don't think i can do much better than that. is there anything i can do to improve on that other than a gear change? i have 3.73 now. i was told that the aftermarket cold air intakes don't improve anything on these trucks because the factory filter and plumbing will flow more air than the throttle body will. just looking for opinions. thanks.

Join Date: Jan 2010
Posts: 18

August 29th, 2010, 7:35 PM   #2  
i forgot to mention, it is an 02 that i got in January and it is the most awesome truck i ever owned.

Join Date: Oct 2009
Posts: 1,644

August 29th, 2010, 7:42 PM   #3  
Super Moderator
electric fans....a black bear tune..only things i can think of..

Join Date: Mar 2010
Posts: 547
Redding, California

August 29th, 2010, 9:34 PM   #4  
CF Senior Member
Cold air intakes on any vehicle will not help increase gas mileage.
it lets more air in creating a bigger explosion which uses up more gas giving you more power, not better mpg.
It's designed to decrease the temperature of the air entering a vehicle to take full advantage of the engine's power.
Colder, denser air gives an engine the extra amount of power that it needs to perform at it's maximum potential.

8.1 seems pretty excessive to me.
What do you tow? houses? hahaha

Is it an automatic or manual?
1-You could get a highway gear installed and cruise at lower rpm's.

2-you could install a turbocharger. A turbo atomizes the air going in so that when it mixes with the
fuel there is not as much unburned fuel thus giving you better mpg. This well help mostly while just
cruising on the freeway. Not recommended if you have a lead foot like me cuz it could also greatly
decrease your gas mileage if you are constantly calling for a turbo boost.

3-Get a Tenneau cover. The bed creates a massive drag on the truck. Getting a bed cover will make
it more streemline and aerodynamic decreasing the wind resistance.

4-Use Chevron gas. Chevron contains the addative Techron that helps the fuel burn better and more
efficiently geting you increased gas mileage.

5-Use Chevron oil. Yes, even chevron's oil contains additives that have proven to help increase gas
mileage using a superior lubrication addaitive that helps your mechanical parts move more freely.
It is also inexpensive and available everywhere. I use 20w50 chevron oil and will never switch.

6-You could get your EPROM tuned to a more fuel conservative mode.

Last edited by Mille Racer 69; August 29th, 2010 at 9:49 PM.
Join Date: May 2008
Posts: 2,395

August 29th, 2010, 10:43 PM   #5  
Super Moderator
Hi jensonracing77,

Welcome to the Chevy Forums.

A set of new gears out the door(had it done for improved mileage) is about 2000$, with the bearings. Be sure to have the Parameters in your PCM reprogrammed so your speedometer and ABS alarms don't go nutz. You can save 2.5-3.5 MPG with a decent gear change. In your case, I wouldn't recommend going to 342s, if you already have 373s you'll want 323s to see a marked and noticeable improvement in gas mileage. You will see an obvious drop in your hard accelerations, specifically at takeoff, however.

The other major gas saver is a bed cover. An aerodynamic fiberglass cap or tonneau cover (@300$ to 1400$, depending on what get) will save you another @ 2.5-3.5 MPG.

These were the two major gas savers for my 2500HD CCLB, but to spend this kind of money for such radical changes, you have to keep the vehicle for many years to get a payback on your investment. Gas isn't very likely to go down in price very much very soon in all likelihood. I only have a 6.0L engine, so it's hard to claim with any real accuracy that you'll get better or worse mileage from either of these mods.

Join Date: Jul 2010
Posts: 846
salmon arm BC

August 30th, 2010, 12:05 AM   #6  
CF Pro Member
mille racer 69, i dont know how you say a cold air filter doesnt give better milage, it does, maybe not the 8.1 because like he said the stock one is good on that, it could however benifit from a K&N air filter

sythetics in the diffs and engine give better millage especially with such a huge engine

a gear changewill help, but ill bet u tow with your truck so i would go with 3:43 gears

with this i would go with an aftermarket tuner rather than a set tune, so that you can increase the power when you want and put it in economy when you want as well

if you tow a 5th wheel a tonnou cover isnt the option, but if towing with a hitch it will be a good one to get (there are also velcro fabric covers that roll up and wont take up a 6x8 plot in your yard when off the truck)

also platnum plugs goes without saying

if you dont have a small plastic air dam under the front bumper, im sure there are some in the aftermarket this will give you a small improvement, but all of these together could net a very significant improvement. i hope this helps

Join Date: Jan 2010
Posts: 18

August 30th, 2010, 5:18 PM   #7  
Mille Racer 69  8.1 seems pretty excessive to me.
What do you tow? houses? hahaha

Is it an automatic or manual?
LOL, i only tow cars now and then. it may be excessive for the need but at the same time, my dad has a 2002 6.0 2 wheel drive that only gets 13 mpg. i figured if i was going to get bad MPG i was going to go with an iron truck motor with iron heads and not the aluminum 6.0. as it turned out i get better MPG and much more power and an engine that is based off of an old school engine. not that i don't like the 6.0, it has more $hit than i thought it would but i just like the 8.1 better. i looked into Diesels before i got this but the extra $5000 to buy it would never pay for itself in better MPG. it would take almost 200,000 miles to brake even. with having the 8.1 it also has the Allison transmission that i wanted.

thanks to everyone for the ideas.

Join Date: Jul 2010
Posts: 846
salmon arm BC

August 30th, 2010, 7:50 PM   #8  
CF Pro Member
nice! i never even knew they came with the allison, i think all these things mentioned in this thread will give u lots of options for better milage

Join Date: Feb 2011
Posts: 2

February 23rd, 2011, 8:30 PM   #9  
CF Beginner
The bottom line is that other the a gear change the milage with an 8.1 is what it is..Headers, exhaust cat back or not & cold air intakes don't give fuel milage or for that matter even horse power...I have my 8.1 in a 4x4 3500 conversion van & I love my beast, milage or not.. Best of luck Dan

Join Date: May 2008
Posts: 2,395

March 11th, 2011, 6:20 AM   #10  
Super Moderator
At the end of the day, fuel economy is a battle generally won by inches, not by miles.

A good tune up, really good heavy duty truck gas shocks, proper tire inflation,(I only go a couple pounds over normal,no more than 10% overall), a good wash and wax job, it all adds up.

Many times it means the difference between
big sweat or no sweat when you have 1/4 tank of gas left.

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