Improving MPG on 8.1

Garmat · May 31, 2002

The only thing, in my opinion that keeps the 8.1 from being the PERFECT truck is the fuel mileage. Some of the things I have thought about to improve my mileage (which is 9-10 mpg..mostly city) is the K&N Filter Charger, aftermarket muffler, and tonneau cover for the bed. My question is: has anybody done anything to improve their mileage and succeeded? I'm thinking maybe the Hypertech Programmer might help with MPGs too? Anybody done it with the 8.1? Is there anything to those Helix power tower things? Looks like a gimmick to me, but I've never found anybody who has tried it. Thanks in advance for any help!

hosspuller · May 31, 2002

Mileage with the 8.1 is not an issue. unless you're a boulevard cruiser If it is... the mistake was in the prepurchase decision. Should'da got a diesel.

I don't mean to flame here .. but anything that is a significant mileage increaser ... like rear axle ratio, bigger tires, etc reduces the 8.1 capacity to haul or tow.

The bed cover will help with the air drag ... but costs a bunch up front.

Garmat · May 31, 2002

hosspuller,

Well mileage is an issue with me. I'm not sure my truck is a boulevard cruiser as much as it is a 'family truckster'. That is untill I load it down heavy or when I occasionally hook up to a car hauler.

I am just looking for folks who have done any of the mods that I've mentioned and have seen increased mileage....or if they have any other suggestions (short of trading for a diesel).

Colorado Kid · May 31, 2002

I'm sorry. You bought a 4x4 Crew Cab pickup with the largest displacememt engine available in any pickup and an automatic transmision and now you've got a problem with its fuel consumption. Let me guess, it also has 4.10 gears.

I think you bought the wrong tool for the job, but at least you didn't pay for the diesel engine.

A 1500HD will carry virtually as much bed load as your 2500HD and get 50% better milage in the process. It will also tow the car hauler (Unless it's a 3 car hauler) and has exactly the same cab.

If you buy the Helix then W.C. Fields anticipated your birth. "There's one born every minute."

Even if you only get 9 MPG and you drive 1800 miles a month (which is high) you're only buying 200 Gallons/month of fuel. If you got 12 MPG (which would be a miracle) you'd still be buying 150 Gallons/month so at most you'd save 50 Gallons x $1.50/ Gallon = $75/ month which means you'd better not spend much trying to improve your fuel economy.

Drive it less...use the other vehicle to haul the family and it'll burn a lot less fuel.

I'll bet that you could do all the mods listed and still not get over 10.0 MPG in the city...none of those things will help at low speeds, and they might even hurt.

Your truck is very, VERY good at what it was meant to do, but it was in no way made to be an economy car. Having put some miles in behind a 454 I'd have expected worse than you are getting.

dmason57 · June 1, 2002

I have 38k miles on my 01; Highway driving. The best mpg was 14 mpg setting cruise on 70. I do have a bed cover, no other mods though. The worst is city driving and it is 9-10. I am used to it now and I try not to think about it. My next HD will be a diesel. I plan to get at least 200k on this one before I change.

Stepside Z · June 1, 2002

You pay at the pump or you pay the bank, but when you talk about a truck that size you are going to pay.

Garmat · June 1, 2002

dmason57,

Thanks for the cordial reply. I've actually gotten about 13 on the highway and thought that was pretty good. I've talked to some guys with the 6 spd and 4.10s that say they're getting 15. I consider that downright incredible.

Colorado Kid,

Thanks for the math lesson and all the other great advice, but you should re-read my original post. I happen to like my truck alot. The fact that I sometimes get 185 miles from a tank of gas seems to me to be the only thing keeping this truck from being an absolutely perfect truck. I've had two trucks with 454s. I'm familar with poor mileage. I'm simply looking for some ideas on how to squeeze some extra mpgs out of the 8.1.

blk496 · June 1, 2002

I can't blame anyone for wanting more mileage out of a big block. I bought mine knowing that double digit numbers would few and far between, but I could handle a mpg or two increase.

I picked my truck up this afternoon and have realized that I should measure fuel consumption in gallons per mile. Regardless, I'm happy as a clam and if this thing is as reliable as the wife's half-ton, I'll be even happier.

gandolphxx · June 1, 2002

Of all the things you have mentioned the bed cover will help the most, reduces wind drag.

The other thing you might check is running the Direct Hits ignition system, some of the 8.1L AV folks have tried this and results have been positive. You can get it at TByrne Motorsports - one of our preferred vendors

BTW; oil and gas consumption settle down after about 5K miles, even better at 10K, and synthetic will also help and doesn't cost an arm and a leg.

JimDandy · June 2, 2002

You could trade it in on a S-10 crew! j/k

I am getting 9 mpg, 75% city. That is why I have a car, too. This is with a tonneau, 3.73 rear, gentle right foot, but 255/85's - they cost 1 mpg.

On the other side, there are a few things to try:

-tire pressure - maintain high pressure (65 front, at least 55 rear when unloaded), it will ride a little rougher, but roll easier.

-switch over to 87 octane if you are running something higher. The gas was good for about 1 mpg with mine (ran premium first 5K, didn't believe it until I actually tried it).

-keep top speed below 70, if you can.

Besides, think how muck gas $200-300 will buy vs. something that may or may not get you 0.5 mpg better.

JEBar · June 2, 2002

In the original post a Hypertech Programmar was mentioned. I have two of them and can recommend them as being an excellent product. The problem comes in when you have to buy high test (92 octane) fuel to run their best program. I have gotten slightly better mileage doing so but not high enough to justify the additional cost per gallon. For my Tahoe and Z71, their programmars did provide much better towing ability with a very heavy trailer ....but with the 8.1, that isn't a problem.

CMNTMXR81 · June 3, 2002

LOL!!! I love when people ask me what I drive and I tell them, an extended cab, 4x4, Silverado 2500HD with the biggest gasoline engine available in anything that would be considered a passenger vehicle which then spins through one of the toughest light to medium duty transmissions available on the market. Their comment is always..."oh, you must get TERRIBLE fuel economy/mileage with that!"

Well no sh*t Sherlock!!! I didn't buy it for fuel economy. Fuel economy was the furthest thought in my mind when I purchased this thing!

Other than spending money on big things like a bed/tonneau cover or performance parts that will allow more effective combustion, simple maintanance will help.

Make sure the tires are pumped up more as they will provide less rolling resistance, keep your fuel system clean (I.E. change filter), keep your air filter clean, keep all fluids routinely changed (I.E. oil, trans fluid, rear end fluid, etc).

Yesterday I drove to Bloomington, IL. Before I left, I filled up with 14.221 gallons of gas. When I got to Bloomington, I had 114.3 miles on the trip odo and I used approximately 1/4 tank (1/2 what I filled up with). So 114.3 miles/7.1 gall = 16.076mpg.

On the way back that mileage dipped back to 11mpg but that was due to me disciplining a Pontiac A$$tek at triple digit speeds. The G/F hates when I bounce it off the speed limiter.

Suburbanite · June 4, 2002

I'm sure you could improve your truck's fuel mileage, but at what cost?

Performance Combos runs ads listing various hop-up combos, their theortical HP/TQ improvements & prices for same. Might provide some idea(s) on where to start.

Drawbacks to increasing tire pressure would be reduced tire life (centers will wear out) & possibly harsh(er) ride.

I've seen ads for Jacobs Electronics ignition systems that list HP/mileage before & after for a '90 454SS. Here are the #'s:

Before: 230HP/16.52MPG

After: 242HP/17.75MPG

Don't see how a 454CI/7.4L engine ever got 16.52MPG to begin with, let alone 17.75MPG but ... those are the #'s. Take them for what they're worth.

Good luck.

JimWilson · June 4, 2002

Some of the items mentioned on this forum (as well as a few others) are:

- mass airflow sensor

- throttle body spacer

- increased air intake (K&N or UPD)

- new exhaust

- new chips

There seems to be a bit of controversy about which of these provides what benefits, but they may be worth investigating. A new chip seems to give the most benefit, but as expected, is one of the most expense (the most expense is probably exhaust changes).

June 6, 2002

Hey, you guys back off!

Just because we buy big trucks, doesn't mean we aren't concerned with making them a little better.

Trying to get a few more mpg from a crew cab big block is no different than trying to squeeze a better 1/4 mile e.t out of a vehicle with the aerodynamic qualities of a phone booth!

Garmat, I have looked at this problem for a long time with my 1 ton CC 4x4 350. I figured, based on what I'd read here and on other bulliten boards, that it would cost me around $1200.00 to get my highway mileage from 14 to around 16. $1200.00 will buy a lot of gas. I just decided to live with it.