Seeking advice for MPG enhancements, 1993 GMC 2500 Suburban

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I'm seeking advice on accessories or kits to improve mileage on my Suburban. I am considering a K&N filter kit (FIPK - Fuel injection Performance Kit)
for the intake side, and am looking for suggestions for exhaust. Borla does not make a system for this truck, any suggestions would be welcome. I'm looking for mileage increases, however small, and hoping not to make it sound like a teenager's hot rod (I'm 43 with a family, my wife wouldn't appreciate radical sound). I realize 'm going to get some sound increase and tone change with he K&N and any performance exhaust system, just trying to keep that to a minimum.
I've looked into programmers and aftermarket ECM chips, but they appear to generally improve performance, not mileage, so I've set those aside for now.
I've also toyed with the idea of changing the final drive ratio. The rear end is a Dana full-floating axle with locking differential (factory stock), if anyone knows how big a job it is to change the gears, I might consider swapping gears when switching between towing and non-towing jobs. I looked at aftermarket Over/Underdrive auxilliary transmissions, but they're $3,000 and up, and the payback is really long.
Replacing the entire vehicle with a Geo Metro (or any other economy car that can't carry 3000 pounds or tow 8,000) is not an option. This is a working truck and payload requirements apply.
Vehicle specifics: 1993 GMC 2500 Suburban, 8,600 GVWR 5.7L (350cid) TBI 4L80E transmission, 3.73:1 final gears
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Sandman
93 GMC 2500 Suburban, 78K miles
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Sandman wrote:

Full floaters are fairly easy to work on but it's not something I would want to do more than once or twice a year.
I wonder if a two speed rear end could be relatively easily installed in this vehicle? If there is one small enough.
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Greetings,
If you are seeking mileage gains from "performance" add-on equipment then you will be sorely disappointed. The fractional percentage that you might see from something like an aftermarket intake and exhaust (heavy emphasis on "might") would take years to pay off on the investment in equipment, provided that the entire time you could manage to keep your foot off the accelerator. Frankly there is not much that is going to drastically improve your MPG that just comprehensive preventative maintenance and a light foot won't. Realistically, you are driving a 13 year old truck that weighs like a tank - you're behind the 8-ball going into this project. In addition, you only drive this truck 6000 miles per year so it will take you next to forever to make back almost any money you sink into it for better mileage.
You need to keep in mind such drawbacks to certain aftermarket equipment as well. Take a high-flow air filter, for example. Typically, the higher flow is only available at the peak airflow requirements of the motor (translation - at top RPM's), and that is not the place you want to be for best mileage. In addition, better flow through the filter also means less filtration efficiency which in turn could lead to a dirtier motor and accelerated wear. Believe it or not, a stock paper air filter flows more air than your motor will ever need at the engine speeds you want to be at while giving you the best filtration. And like what has been mentioned many times before, the exhaust systems that you probably are looking at are all designed to provide better power and sound but not so much an improvement in mileage. Add into the equation the shear cost of an exhaust system and it will also be a long time before you break even on such an old truck. People who add this stuff to their vehicles have to have realistic expectations of what to expect (sound and power) and what not to expect (a significant increase in MPG). Dyno tests for many of these products can be very misleading. They are all done under hard acceleration at wide-open throttle (or close to it) which is not where you're going to be 99% of the time on a daily driver.
You say that payload requirements apply, but depending on what you have and what you need you may be able to move down to 3:42 rear gears which will get you an extra MPG on the highway (lower engine RPM's) and still be able to handle a decent payload, but don't expect to efficiently haul 10,000 lbs with that set-up (especially from a dead stop or at top highway speeds). Changing rear gears and tire sizes is all about give-and-take, and you may not be happy with what you finally get for what you had to give.
If you really want better mileage in a truck that does what this one is required to do, then your money is best spent buying a newer Chevy Crewcab with the Duramax diesel. You're going to have to spend some serious money, but at least you will get a truck that will do what you want it to and give you decent results in the end.
Cheers - Jonathan

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On Sat, 31 Dec 2005 18:42:31 GMT, "Jonathan"
(snip)

===========Your crew cab Duramax suggestion is perhaps the most practical one, particularly since the expected driving of this vehicle is projected to rise to 25K miles per year.
I have a 2003 CC Duramax and regularly get 20 mpg or better in freeway driving.
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Thanks for the quick, and I would say rather expected, responses.
I have, of course, already implemented the solution of slowing down. 65MPH vs 75MPH and very easy acceleration (to the irritation of leadfoots that tailgate off the start line) yields 1 or 2 MPG, and I have been doing that for years.
The 6000 mile per year figure is correct up until earlier this year. The accumulation will be 25K per year from here on.
As for trade-in, the vehicle has only 78,000 miles and works perfectly well and will do so for 200,000+ more miles. It's hard to spend $40K ($30K after trade-in) on a new one that will save me $8K worth of fuel over the same time period (assuming the new one gets 20MPG) and dramatically increase maintenance costs. My 02 Tahoe costs triple to do anything compared to the 'Burb and gets 19MPG with the same gear ratio. Fuel filters, cabin filters, thermostats, everything costs WAY more than the parts for the '93.
I'll continue going easy on the throttle and keep reminding myself that gas is cheaper than a new 'Burb......
Thanks again for saving me $250 on the K&N. I think I'll look at changing the gears, or see if I can find a 2-speed or aux tranny that will actually pay me back before 250,000 miles. My trailer pulling activities are limited to short distances and 1K or 2K miles a year, so some compromise in hauling capacity is possible. Ideally, I'd like the 2-speed option to have the best of both worlds.
Sandman
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Sandman
93 GMC 2500 Suburban, 78K miles
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Other than trying to pace the leadfoots in traffic which is the norm nowadays, resulting in much wasted fossil fuel. Have been using the original Mobil 1 for years. That will save gas, even over the standard petroleum oil with user added additives. If you have overly wide, big tires, that adds to fuel consumption as well. Use the factory recommended size and inflation rating if not little over inflated not exceeding tire inflation spec while the tires are hot.
Hauling trailer is a different matter for tires. You need a wider tire for the load, and for stopping grip.
An OD aux tranny would be good for non trailer loads on the highway.
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Jonny
"Sandman" <REMOVE snipped-for-privacy@REMOVEyahoo.com> wrote in message
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Put the big ole Burb in the garage and buy a metro or cobalt or somthing cheep on gas. You would save the extra $$ alone in fuel

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Cheers - Jonathan
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Put the ole Burb in the garage WHEN you do not need it's towing or hauling. Use a smaller, more fuel efficient car for routine tasks. Of course, if you need the payload 25K miles a year , then you have fewer options.

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So how many years is it going to take to make up the $17,000 cost of a Chevy Cobalt just in fuel savings? Let us not forget the additional costs for maintenance, insurance, registration, etc. Please remember the OP was essentially asking how to IMPROVE his Suburban, not REPLACE his Suburban. So just how is buying another vehicle "improving" his Suburban? He specifically stated "Replacing the entire vehicle with a Geo Metro (or any other economy car that can't carry 3000 pounds or tow 8,000) is not an option." Am I the only one who read this?
Cheers - Jonathan

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You are missing something here, if you drive a lot, the fuel saving will pay for the econbox. When you do not need the tank, the econobox is easier to park too, maintance is cheaper and so are it tires and the big plus here is the tank/SUV will last a LOT longer. I have a 89 4x4 burg that I goot new and is still pretty cherry and though it has 175K on it, they are mostly hiway miles from over a dozen cross country trips. I drive it when I need its capabilties, not to go to the store or work and it still has a lot of life left because of this. I also have a 2000 K3500 that only has 34K on it because I only drive it when I need a truck and it has many years of life left too.
Jonathan wrote:

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You can get a plain jane 05 cobalt for 10,500

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Have you considered a new F150 with the new more efficient three valve V8 and a five speed tranny?
mike hunt

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Mike Hunter wrote:

I have a friend that bought a 2005 F150 with auto and my 2004 Silverado gets batter gas milage. If your going to suggest a new truck you might as well get a new Chevy, 2007's are supposed to have the DoD to get better milage.
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Do a search of the EPA guide, you will find the 2006 three valve SEMFI OHC V8 engine in the F150 has better fuel economy than does the 2006 Silverado. A further search will reveal the F150 also has a greater standard towing capacity as well
mike hunt

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Greetings,
I don't know where you're getting your data, but according to the EPA fuel mileage guide the 2006 Chevy 1500 2wd with the smallest V8 (4.8L) gets 16 city/21 hwy. The 2006 Ford F150 with their smallest V8 (4.6L) gets 15 city/19 hwy. Both the 5.4L V-8 Ford and 6.0L Chevy gets 14/19, but the 5.3L Chevy gets 16/20.
I am comparing 2006 half-ton 2WD regular cab trucks. You can find the data on this website: http://www.fueleconomy.gov/feg/findacar.htm Interestingly enough, the fuel mileage for the Chevy with either the automatic or the manual tranny are the same. While this guide does break down each model by year, engine, transmission, etc., it does not specifically state that the Ford has the 3-valve SEMFI OHC motor - it lists motors by displacement only.
Cheers - Jonathan

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Those test are far for valid and even the EPA admits they are greatly in error at times and vowed to have a new test by 2007 or so that is more realistic. You should hear the way the "cheat" on those tests.
Jonathan wrote:

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That is not half the vehicle that old burb is. Keep the burb and get a cheap commuter car too.
Eugene Nine wrote:

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I'd try Duralube and highway tire tread with a high pressure setting, for a 5% possible fuel saving.
Also keep it well tuned and drive crisply but not heavy footed. If you are holding many average drivers up on acceleration you are not crisp enough on acceleration.
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IMHO; you can spend a lot of money on this 'tank', and are unlikely to ever make substantial improvements in gas mileage.
The exhaust system is not likely to gain you anything. K&N filters either.
The rechipping and fuel injection management is an unknown quantity AFAIK.
Run synthetic lubricant for the fractional improvement you might obtain, air up your tires, and keep the thing in tune as much as you can.
The twospeed tranny add-on might help, but that costs a couple of thousand bucks as I remember it. They could be transferred from one car to a similar configuration if you ever wanted to do so.
Drive like a little old bluehaired lady, and you will improve your mileage a little bit.(of course, you may never get to your destination, but your mileage may be a little better ;>)
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