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Increasing gas mileage for a daily driver

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Hobbes9112

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Bonner Springs, KS
Hi-

I just bought an 85 Jimmy last week on ebay. I am waiting for it to be shipped here from California. I got a great deal on it. It is in great mechanical shape with no rust. It only needs a little interior work. I was really excited about it until gas prices spiked this week. :mad: I am not going to be doing any off roading and I will be doing about 90% of my driving on the highway. I was driving a 96 s-10 with the 4.3 high output. I was getting about 20mpg. I decided to buy the Jimmy because I got tired of having a vehicle I can't work on because of the computer system. Besides that, the 2wd doesn't do too well in the snow even with 500 pounds of sand in the back and the ABS system has been acting up.

I drive about 300 miles a week to and from school. I am working my way through college and I don't have a lot of extra money to waste on gas. I am making a little money by selling my truck and I am trying to find ways to increase the fuel economy on the Jimmy.

It has a freshly rebuilt 305 with 1000 miles on it and about 500 on a rebuilt tranny. It is all stock with 32x265x15 tires. I am thinking about doing some of the following: Narrower tires (it needs new tires anyway), carb spacer, dual exhaust, upgrade the distributor/ignition, upgrade air filter/air intake system. Any suggestions on what would give me the best bang for my buck and what things would make no difference? I would love to keep the Jimmy but if I can't get better than 15 mpg I will have to sell it and keep my S-10. I am afraid of what it will cost to feed this thing during the summer when gas is $2.25 a gallon. Thanks!!!
 
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you will be getting 15 with some tuning and some small mods like the exhaust and intake. Volant makes some awesome cool air intake system that have produced 15-23 rwhp because of the poly ethalyne air tube and filter intake position... but if your gonna put some exhaust on for mpg you should go with a single 3" unless your doing it just to have dual exhaust... i always thought dual was better until somebody brought up the fact that your running 2 cats and 2 mufflers instead of 1. A single will do the job just as good, be a little louder and won't kill your wallet like a dual system. A carb spacer may have an affect or it may do nothing at all. I have seen both.

I'm sure you'll get plenty of responses on this one.
 
Even with a baseline of 14MPG or so, it's going to be hard to increase the mileage IF everything works good now. Upgrading the ignition and air intake isn't going to help if its in good shape already. Tune up is always a good idea, if the stuff isn't brand new as is.

The #1 thing to do short of making sure the engine is running as best it can, is to drive slow. Big difference between 60 and 75MPH.

Not sure what the tire size actually is, but if they are really 32" diameter, then they are likely 11.5" wide. Narrowing tire size will help in economy, but how much is going to be pretty hard to determine. Probably not worth the cost of 4 or 5 new tires compared to running what you have.

These things just aren't economical, no matter how you slice it (except diesels, if low 20's is economical to you) but as long as you are shooting for 15MPG or so, you should be able to get it there, if it's not already.

My freeway best with my '83 K5 was 17MPG with a carbed 305, OD, and 235/75R15 tires. Fairly loaded down at the time. City MPG was always in the 10-13 range, even with my current setup.
 
By federal law, yes you do. Will it hurt to remove it? No. Will it help anything to remove it if it's still in good shape? No.

You can actually test your exhausts backpressure (or have it tested) fairly easily, just need to get a pressure gauge before the cat. The maximum backpressure figure I have seen listed in factory service manuals. Thought it was like 3-5PSI. Anything over the factory max. spec, something is clogging the exhaust and will cost you power.
 
not a fuel sipper...

ANY GM full size wont get much more than 15mpg,unless its a diesel,and they only get about 5-7 more mpg than a gasser...I think the best way to save gas is to stay home!-:blush: -I have tried everything to increase my gas mileage,since I'm not working now,and despite having everything tuned up and in good condition,even my 79 C10 with a 305 only gets between 11-14 mpg on a good day--and since we havent had any warm weather this winter,the gas goes even faster,the cold is murder on gas mileage,its always on choke and cold engines= poor mileage...
I plan on working more and driving less in the future,just to be able to survive,it takes more money to live every day--not much of a life,but thats the way our world is getting--life sucks,then you die--and you pay thru the nose every day inbetween....they never taught us this in school..:frown1:


Like Merle Haggard sings--"Are The Good Times Really Over For Good"?:confused:

Diesel fuel is even more than gas all this winter--I just paid 2.19 a gallon,and the guy at the counter said its going up 25 cents at least in a few days--and so is gas...I wonder how long the truckers can continue to drive their big rigs at 0 profit??--bet they will go on strike,then EVERYTHING will go way up--not a good sign for our economy...I'm wishing I hadn't sold my 86 VW Jetta diesel,it got 43mpg...:frown1:
 
my uncle drives his own 2002 big rig.... can't remember who made it but they give him raises when the prices go up.

a 79 c10 is alot heavier than an 86 jim isn't it?
 
diesel4me said:
ANY GM full size wont get much more than 15mpg,unless its a diesel,and they only get about 5-7 more mpg than a gasser...I think the best way to save gas is to stay home!-:blush: -I have tried everything to increase my gas mileage,since I'm not working now,and despite having everything tuned up and in good condition,even my 79 C10 with a 305 only gets between 11-14 mpg on a good day--and since we havent had any warm weather this winter,the gas goes even faster,the cold is murder on gas mileage,its always on choke and cold engines= poor mileage...
I plan on working more and driving less in the future,just to be able to survive,it takes more money to live every day--not much of a life,but thats the way our world is getting--life sucks,then you die--and you pay thru the nose every day inbetween....they never taught us this in school..:frown1:


Like Merle Haggard sings--"Are The Good Times Really Over For Good"?:confused:

Diesel fuel is even more than gas all this winter--I just paid 2.19 a gallon,and the guy at the counter said its going up 25 cents at least in a few days--and so is gas...I wonder how long the truckers can continue to drive their big rigs at 0 profit??--bet they will go on strike,then EVERYTHING will go way up--not a good sign for our economy...I'm wishing I hadn't sold my 86 VW Jetta diesel,it got 43mpg...:frown1:
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Well, I have a crappy story too.. I spent a long time on the inlaws' 67 camaro restoring it and making it nice a while back. It turned out extremely nice. So, then I roll in the Datsun 510 project and in the middle of that the inlaws get a 69 Olds. So, in their good gesturing, they send the car to my folks' shop. $2500 later, my wife, her dad, and 2 of my kids go 50 miles from home to pick up this car, with pretty high expectations. The car makes it about 2 blocks before dying. So, my wife's pissed, expresses herself to my folks, next thing you know my mom's screaming at me about respect for a half an hour while I'm looking at my stuck trailer. And what did I do to deserve all this? I didn't have time to do another freebee for the inlaws and instead of my parents taking care of the goddammed car they ford up. So, finally, it shows up in my driveway on the hook, and my old man says that it now has a rod knock and my mom's crying. I was a nat's ass away from starting the K5 project but now I get to work on a 69 oldsmobile and reunite families. Funny how my wife, the kids and I are a totally happy family finally, and it takes my folks to ford it up.
 
Why be someone's doormat? Tell em to go pound sand and take care of their own problems instead of dropping them in your lap.

Rene
 
That is when the rules apply the most. If I offer to help that is one thing, if they take advantage and drop it in my lap they can go pound sand. I have a life and projects of my own...

Rene
 
I want my mom to let me do the work instead of her paying 800 bucks for a new clutch when i could do it in a few hours for 150.

she also paid 2000 for heads and head gaskets and then another 3000 for a rebuild... me and my bro or dad could have had it all done for 600.
 
dirtwarrior17 said:
my uncle drives his own 2002 big rig.... can't remember who made it but they give him raises when the prices go up.
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It's called a fuel sercharge. We increase our rates as fuel goes up, it's the only way we can actually make money. I am worried that soon when fuel hits $3.00 a gallon our customers will use different alternatives to ship their products than use us because we have to raise our rates high enough to still make money, but out of their price range.
 
A single will do the job just as good, be a little louder and won't kill your wallet like a dual system
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A single system is quieter than a dual setup. I do agree that a single system is more economical but that sound of duals can't be accomplished any other way.

Hobbes9112,

If you are tight on cash I would suggest you do nothing to it out of a good tune up. :) AFtermarket air intakes and filters really don't do a whole lot, your engine can pull plenty of air through a good paper filter and the factory air intake is decent. Exhaust would help a little but once again, not enough to pay for itself in fuel savings anytime soon. Save your money and just make sure it runs the best it can stock.

I decided to buy the Jimmy because I got tired of having a vehicle I can't work on because of the computer system.
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I hate to burst your bubble but if that truck is a California equipped '85 it has a computer controlled carberator and distributer. :blush: It's a lame system IMHO. My '85 HAD it but doesn't anymore and runs better than it ever did.
 
I don't think the Jimmy is California equipt, but I won't know for sure until it gets here. I know it didn't go to California from Nevada until about five years ago. If it is computer controlled, that will probably be one of the first things to go. That is if it isn't a horrible job to do.

I am going to make about $1200 dollars above and beyond what I paid for the Jimmy after I sell my truck. I need to put a little money into the interior and buy new tires. I could put this money away for gas, but I figured as much as I will be driving the Jimmy, it would be nice to invest some money it it. I know there isn't one miracle cure for the fuel economy, but I hope by combining a few things I can at least make a dent in it.
 
Swap a 6.2 in it and you'll get 20-24 mpg out of it no problems at all...and it'll wheel a lot better than a carbed gas engine.

My two cents...

Rene
 
A single system is quieter than a dual setup. I do agree that a single system is more economical but that sound of duals can't be accomplished any other way.
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If you do some searching you'll see there was a discussion about this....

we all agreed that a single 40 flow master is louder than 2 40 flows. I have a 3 inch single with a race flow magnum(generic flowmaster) and i have a couple buddies that run duals and at idle the duals are louder but get the rpms up and its a different story. think about it... instead of 2 cats and 2 mufflers your running 1 cat and 1 muffler....

I think the post was called flowmaster 40 or something like that.
 
I can definitely see where two mufflers would make a quieter ride. I am not too worried about the sound as long as it doesn't have too much road noise. I am not looking for a performance beast. I have my Camaro for that. I am just trying to decide on the benefits of ditching the stock exhaust for something with better back pressure. I am concerned about fuel economy more than hp gains.
 
This is turning into a hi-jack...

Anyways, exhaust size needs to be factored in when comparing single to dual. Dual 2.5's will outflow single 3". The volume of exhaust trying to flow through one half of a dual system is half that trying to flow through a single system. A 2.5" pipe has a cross section of 4.90 square inches, compared to the 3" pipes 7.06 square inches.

Less exhaust volume per square inch = freer flowing exhaust.

FWIW, my 2.5" dual 50 series Flowmasters were freaking loud at WOT and 5500 rpm, much louder than any single system I've ever heard.

Rene
 
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