View Full Version : MPG increase add-on

04-18-2000, 01:55 PM
Has anyone tried any type of add-on gadgets to increase your vehicles MPG? With gas prices what they are, I was thinking about trying one. But I don't know if I'll just be throwing away my money. Currently getting around 8-9 MPG on my 77 Chevy 350 4X4 4 barrel. Did the tune-up thing, bought all new stuff. Even the more expensive sparkplugs. Adjusted my idle...carb, verified my timing. No misses, it sounds great. Installed transfercase part time convertion kit. Speedometer is off just a little bit ~ 2 MPH at 55. I drove &quot;normal&quot; while trying to figure out my gas mileage, don't really hotrod the truck. About half stop and go and the other half highway driving. Replaced all gas lines, no leaks. Best I can seem to get is 9 MPG. If someone has tried one of these &quot;add-on&quot; for better gas mileage and it works please reply. Actually let me know about your experience either way. Heck I would be happy getting 12-14 MPG. <p>A little more reading if your interested. So everytime I talk about these &quot;75MPG,100MPG carbs that &quot;once exsisted&quot;, I get chills down my spine. Feels like the government,oil companies are watching. Been doing some reading on the internet, specially the government patent database. Found hundreds of so called invetions that increase gas mileage, cleaner burning, more horsepower. Have any of you older folks ran across any of these things? The only thing I can think of is the people who knew, some how dissapeared.<br>So, if I post a message stating that I found an add-on or carb......that will probably be my last message I send!

04-18-2000, 10:48 PM
What transmission are you running? If it is a manual 3 speed and you have say 33x12.5 tires the gas mileage you say your getting is about right. Try running narrower tires. I have a 87 V-10 with 32x10.5 x15&quot; tires and the 700-R4 ( which is really a great tranny) and i,m getting 15mpg on the highway. On the other hand, my 88 K-5 Blazer with the same drivetrain is getting about 12.5mpg. All the gas saver carbs run smaller jets(starve fuel).<br>Performance will suffer and so will idle. Good luck. JB

04-19-2000, 09:58 AM
My 77 silverado is running a turbo 350 tranny, 203 (converted to part time) transfer case, 350 motor with a quadra-jet carb. 4&quot; lift. Tires are 33*12.5*15. Another thing I will try for better gas mileage is; Going to fork over money for alignment(looks ok, drives fine) will re-balance the tires. And since just a few weeks ago I cracked my tranny(just before the transfercase)while 4 wheeling, I will need to replace it. Thinking of a 700r4. Anyone know how much they cost? What year is best(or what year tranny to avoid) Should it bolt right up? Any info appreciated.<br> <br>Injured and bleeding tranny fluid my trusty chevy still managed to get me home(20+ miles). Yeah it was my fault, didn't bend the retainers on the tranny mount bolts so I lost 1 bolt and the other was really loose. Will keep updating on gas mileage improvements. But if anyone has any other ideas to better my MPG, I would sure like to hear them. Seems like every other 4x4 with about the same set-up I have is getting 12-17 MPG. I'd be happy getting mine to 12-14 MPG.

04-19-2000, 04:44 PM
I recall hearing that the first few years of the 700r4's were pretty bad. I blew up one in my 83 1/2 ton after just 70,000 miles. I'd look into a B&M or Jet Products reman of that tranny, as they know all the things to do to them for more strength. I got mine for around $1600 from a local tranny shop I believe. I wouldn't be suprised if you could get it cheaper than that though. I don't know what you think about diesel's, but as far as your mileage goes, an old 6.2 could help you out a lot if you found a good one. I just bought a 2 wheel drive one that I've been using for my highway rig, and to and from school, and I'm getting between 18 and 22 miles to the gallon. Not bad for a really clean $2,000 truck.

04-19-2000, 05:59 PM
Well My 84 700R4 left me stranded, But I new it was Going out. I really pushed the inevitable. Your fuel economy sounds about right for what you have. I get around 12 to 14 on my K20. I do like the overdrive. If I were doing a 700R4 swap I would look for something between an 84 and 87. I think those were the years before a lot of the electronic controls went on them. The transmission will bolt right up to the engine but IM pretty sure it would require some adapters. Or A different transfer case. I never did a swap like that, Just heard of such things. Good Luck.

04-21-2000, 01:08 PM
Hi, I live in the U.K. where my 86 k30 is doing about 8-9 mpg. I hear you bitching about fuel price but it costs me the equivelent of $220 to fill both tanks. bet yours dosn't seem so bad now??

04-23-2000, 04:30 PM
What gears are you running? Also the fact that your speedometer is off could effect your mileage calculations. As far as alignment, there is only one adjustment that is possible on the solid axle; toe in. It should be adjusted to 1/8th&quot; toe in. You can do it yourself very easily and save yourself $50 or so bucks. JB

04-23-2000, 05:57 PM
JB - Was thinking of &quot;starving&quot; leaning down my fuel to the engine. Do you know if autopart stores sell just the jets for the qaudra-jet carbs? I'd like to try and put smaller ones on. <p>Also forgot to mention that I have a K&N filter but it didn't seem to help out. As far as my gears.... don't really know. I imagine there stock for that year truck. <br>I balanced the tires and will be driving around with the tailgate down. If having the tailgate down helps I will build a tailgate that will allow air to flow thru.<br>I'll let you guy's know what happens.

04-23-2000, 06:21 PM
If you lean down too far you may get detonation problems started. That could lead to major engine damage rather quickly. You may also have to go to a much wider plug gap to fire the lean mixture. A friend of mine was messing with lean carbs back in the 70's. He was using electronic ignition before Chevy had HEI, and at one point he had gone so far as to remove the side electrode from his plugs. He had juice enough to fire across that wide gap and he was jetted pretty lean on his Q-jets. I don't know how he did make out for mileage, I just know he was running big blocks and tall gears, 3.08 or less ratio

04-23-2000, 09:03 PM
I know JC Whitney sells carb re jetting kits, I think they also sell carbs too. It would help to know what gears you are running though. If you have a 3/4 ton truck and a turbo 350 you probably have high gears. That would be why you use so much gas. JB

04-27-2000, 12:08 AM
Well, I got my mileage up to 10.5 mpg. Half highway driving and half stop and go. Guess balancing my tires and driving with the tailgate down helped out. Just need to work on making a new flow-thru tailgate. Checked my alignment today and the &quot;toe-in&quot; was off just a little bit. Thanks for the tip JB. Also checked the jets in my carb, they were 64c. Performance store I went to only had 65? Does anyone know if thats the smallest jets they make for the quadra-jet carb? <br>I'm pretty sure my 1/2ton 4x4 is running 373 gears. Looked at Chucks info and there where only three possible gears. Anyone know how I can fine out for sure? <br>There are two other things I wanted to try but the 700R4 tranny didn't seem like it was a good idea. Tranny shop said I'd have to use an adapter, but it was pretty weak. Or I'd have to have one specially rebuilt. Too much money. The other is an electric fan. Seen a post on another website that said it increased mileage by 2 mpg and increase horsepower because the engine didn't have to drive the fan. Anyone try the electric fan? Does it keep you vehicle cool? If anyone has tried this let me know. I think the electric fans run about $90. Want to hear pros and cons before I make a decission to buy one.

04-27-2000, 07:32 AM
The engine still has to &quot;drive&quot; the electric fan, just doesn't have to power it all the time. Cruising down the highway you get enough ram air through the radiator to do most, if not all, of the cooling.

04-27-2000, 12:57 PM
I had a friend who completely removed the fan on his 1966 el camino. It had a pretty hot 327 in it, but he used it mostely cruising on the highway, and it never really gets too hot up here in the pac northwest anyway. Depending on if you haul a lot of stuff, or pull hills in low gear, off road, stuff like that, I'd get one or two cooling fans. By the way, the guy in the el said he saw 2-3 mpg increase. Take into consideration though, that he had 4.10 gears and no overdrive, so his engine was always turning that fan pretty fast. Good luck, tell us how it turns out if you go for it.

05-08-2000, 04:43 AM
About your gear ratio, there may still be a small metal tag held on with one of the front diff cover bolts that will have the ratio on it. 700R4 will require adapters ($$)to swap out. Electric fan good for water crossing also, can turn off so engine isn't covered w/water. Lastly, figure out how much money you spent trying to get that extra 2-3 mpg, then figure how many gallons of gas it will take you to recoup that expense. More than likely it will take at least a year. Trying to gain mphg is very tough to do without spending so much money that it takes forever to make up the difference. I get 9-12 mpg with my K5 and 3.73:1 gears.

05-18-2000, 10:07 PM
I have a 78 k20, with sm blk 400/ turbo 400 tranny, 4:10 gears, 140k miles w/o rebuild, just drove from Washington state to Texas, and averaged 12 mpg, &quot;tail gate down&quot; tail gate is the only thing that I have found that makes any noticable difference in fuel economy, especially on highway. I get 9mpg in city, I too have tried every different possible little trick for improving economy, seems the only thing left is to either go shorter gears, or to go purchase a fuel injection system, but I think that it will take a long time to recover the $1600.oo for the fuel injection system.<p>keep your fuel filter changed, pcv valve changed and wear a set of slippers when you drive,......that is about the only way I know to help the ol wallet and fuel economy.