how to up my MPG

Discussion in 'Performance & Fuel' started by Andy_Panda, Feb 11, 2013.

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  1. Andy_Panda

    Andy_Panda New Member

    I was curious , how would I up my mpg ?

    My suburban is a 1995 , 1500 with a 350 I believe ...and it has a carburator

    I know by experiance with past vehicles that spark plugs , CAI , and a few other things help , but I've never owned a vehicle with a carburetor so what can I do . I currently get about 11 city 15 hwy ...completely stock , new fuel filter brand new stock paper filter and recent oil change ..thanks in advance !
  2. Bighornkid

    Bighornkid New Member

    Andy, Your Suburban should have TBI, throttle body injection, and not a carb. I had a 95 and could get almost 20 mpg, on the highway. Totally stock except for synthetic oil and lubes.
  3. dobey

    dobey Member

    As said already, it's not a carb, but a TBI system (which looks like a carb, but is just a big throttle opening, with a fuel injector).

    Biggest things that will help you is keeping the engine oil, filters, and fuel system well maintained; and keeping the tire pressure up near the max for your tires (probably around 42 PSI), keeping the load down (empty cars are lighter cars), and keeping your foot out of the floor when accelerating.

    Plugs won't really help (unless yours are worn out, or poorly indexed or gapped). A CAI kit for your truck won't really help either, as it doesn't eliminate what appears to be the problematic piece in the intake tube, which is the neck on the filter housing. A filter housing that kept the neck leading to the air intake tube on the side, more close to round, would be helpful, but probably not enough to get excited about.
  4. Andy_Panda

    Andy_Panda New Member

    Thanks guys . I usually stay at around 2000 rpm or lower to save gas and tire pressure is fine ...could be that the motor has over 300k miles on it lol . I was just hoping there was some mods or something that I could do to increase the mpg . I have the original dealer paper that goes in the window and it says 13mpg hwy
  5. dobey

    dobey Member

    Well if it says 13, and you're getting 15, sounds like a win to me. :)

    But there isn't really much you can do on the older TBI engines in ways of simple mods to gain a MPG or two. And that's all you would get, if you could do the mods to get them. There's one injector for all eight cylinders, and it's at basically the furthest reasonable point from the intake valve that it can be. So you can't really do much in the way of tuning. The intake system doesn't have any huge/odd bottlenecks that a CAI would help get rid of. The main issue with the intake system is that it goes from a 3" circle to an almost flat rectangle at the neck of the filter housing.
  6. vncj96

    vncj96 New Member

    I disagree, you should be getting better, when my parents had there 92 we could pull 22 mpg at 75 mph loaded with three kids and luggage. The old TBI are much easier then the vortec motors to squeeze more mpg out of. New distributor, wires and plugs will help greatly. Also have you ever changed diff fluids? Just getting some new fluid in the rear differential will help. Just get a stock replacement K&N and make sure the timing is correct.
  7. TimTom64b

    TimTom64b New Member

    What's your tire size? I lose just about 3 miles per gal with my larger more aggressive tires versus my stock old man winter tires. Other than that... ya need to keep you foot off the throttle...:)
  8. Andy_Panda

    Andy_Panda New Member

    Lol my tire size is p235/75R15 so I don't think its the tires
  9. marksoldtowne

    marksoldtowne New Member

    Best way to uo MPG are accelerate slow and gradually get to the speed desired.Accelerating fast at stop signs and red lights is not needed,because you are using three times the gas needed every single time you do this,.Proper inflated tires, most tires run at 40 psi, some a little less, keep proper air pressure as often as possible.) clean proper gapped plugs is always best, if a plug has build up of carbon on it it will not function as good and will use more fuel to get the job done.Oil should be kept in clean to decent condition,change it when needed to get better performance.
  10. phoebeisis

    phoebeisis New Member

    I looked up EPA site-the mpg ratings-
    I will post 2 sets 2 for 2wd 2 for 4x4
    The 1st is the rating on your window sticker-the second is for the revised rating(revised 2008)

    2wd original ratings 1995 city=13 combo=15 hy=17
    2wd revised 1995 city=12 combo=13 hy=16

    4wd original 1995 city=12 combo=13 hy=15
    4wd revised 1995 city=11 combo=12 hy=14

    The original 1995 combo rating for 4wd was 13 mpg
    In any case your 11 mpg city- is not bad-and indicates your vehicle is in decent shape despite miles and years
    Now 15 mpg hy- is what you would expect at a steady 70 mph or more- or if you have a little city mixed in-which is the usual case

    Your mpg sounds ok
    You could improve your city mpg by pulse and gliding.The old "drive like you have an egg under accelerator" doesn't work as well as pulse and glide.
    Our transmission-most GM truck ATs- are perfect for pulse and gliding because they "disconnect" when you lift your foot completely off the gas-no engine braking at all-just as if you put it in N when it is still in D

    Motor on Pulse and glide is worth about 5-10% more than egg under accelerator- 15-20& more than driving normally
    Pulse and glide-
    Just accelerate normally-not gently-up to posted city speed limit-lift off-you will actually peak at about 37 mph if you lift at 35mph- then glide down to 28 mph- you glide will be about 27-30 seconds and it will carry you about 1/4 mile.So one pulse glide cycle will be about 1/3 mile-
    In many cities this will carry you from light to light
    If not just repeat.
    GM engineers removed engine braking in the ATs-clever transmission trickery-to get you better mpg
    Partially Explains part of how they get such good mpg from 5000 lb BLOCKY V-8 powered vehicles.

    Pulse and glide-with motor on and left in D- works great in GM trucks
    PS as other said-tire pressure important-CAI exhaust mods all motor bolt ons-waste of money for part throttle FE- GM engineers know their business-forget trying to beat them with some BS bolt on-won't happen

    PPS- your 3rd row weighs about 80 lbs-if you don't need it-remove it- but you won't be able to measure the improved FE- 80 LBS 1.6% weight loss- figure maybe improve city FE by 1/2 that at best-much less than .1mpg

    PPPS Syn oil say mobil 1 5w30 will help FE -but not enough to measure-same store on syn diff lube-good idea-but you won't be able to measure any difference-many folks swear by amsoil or royal purple

    My point on modifying how you drive will produce gains you can measure-and our GMs have the ATs that are designed perfectly for motor on P&G -
    dropping hy speed improves mpg measurably also-
    depends on local conditions but you can usually run 4 -6 mph less than posted limit without getting run over from behind-some places you can't but most you can
    Last edited: Aug 15, 2013
  11. Family Force 6

    Family Force 6 New Member

    Thanksphoebeisis for the info on the pulse and glide. That's what I've been doing the last couple of years driving and have noticed a measurable increase in fuel economy. I usually pulse up to about 40 to make sure it gets in to OD.

    According to other GMTC forum members an electrical cooling fan system is one of the best ways to increase power and efficiency. There are several write-ups and posts that deal with that. One of these days I'll get around to doing it on my 99 Suburban.
  12. phoebeisis

    phoebeisis New Member

    Yes the electric fan should improve FE-
    Our other car-Prius-has electrical fan electrical steering- electrical AC compressor-
    yeah anything you can do to take some constant load off engine-pulleys etc have to be spun even when they are clutched-good idea
    What sort of fan do the later 5.3's have?? If it is electrical-safe bet it is because electrical is more efficient-mpg and HP- a FREE LUNCH

    I think our older 5.7 have clutched fans-helps some-but still losing mpg spinning that pulley

    In the "old days" before clutched fans when our 1960's early 70's cars had EXTREMELY HEAVY fans- we would switch them out for FLEX FANS- light weight fans with blades so flex they would flatten out at higher RPMS and free up so HP. And they were lighter-so freed up some accelerating hp
    Back then those fans felt like 5-7 lbs
  13. Family Force 6

    Family Force 6 New Member

    I remember installing a flex fan on my 75 Camaro and not only was it lighter but it increase in airflow was huge. Plus it was cool to see it flatten out when you pushed on the throttle. Though I read some posters that had experienced rivets loosening and blades flying off after time- YIKES!
  14. phoebeisis

    phoebeisis New Member

    Family Force-yeah they were cool-put one on my 1971 383 Cuda in 1975
    yes they did seem a bit under built -I could picture those rivets letting go!
    But they were cool-and a cheap mod-that actually did what it claimed-more power for the wheels!
  15. dobey

    dobey Member

    Whether the newer trucks have electrical or clutched fans, depends on a few different things. The 5.3 in the 2004 Silverado Z71 I used to have, had a clutch fan in it. The 2009 Avalanche LTZ I have now has a 5.3 with flex fuel, and an electric fan. I think all the new trucks might be electric now, but not certain.

    The Prius has an electric A/C compressor, simply because it would be impossible for it to have a belt-driven compressor on the gas engine, which is often not running when the A/C would need to be on. Hybrids that keep the gas engine idling while running off the electric motors, can use a belt-driven compressor.

    The fully electric power steering is just common now, on cars. Manufacturers have moved to it, as it allows a greater flexibility in design, is cheaper to manufacture and install, and integrates well with other control systems in modern cars, such as ABS. This has been happening over the last 10-15 years.

    And transverse layout drivetrains simply require an electrical fan, because the face of the engine is not at the front of the car, where the radiator is. This has been the case for decades. Nothing special about the Prius in that respect.
  16. phoebeisis

    phoebeisis New Member

    Right-the Prius has to have the AC run off the battery-either that or no ac when motor cycles off-which is every time you lift off the gas much
  17. stchman

    stchman New Member

    One of the best ways to get better MPGs is to simply use the vehicle's cruise control. Many studies have shown 7-14% better fuel economy when using CC while on the highway.

    Another way that won't cost you any more money is to make sure the tire pressures are at their factory specification.

    Clean air filter and regular PCV valve change intervals will help. New spark plugs and won't hurt.
  18. Parkrat

    Parkrat New Member

    My 01 was getting 18 mpg imp in city only, then i started using a fuel additive and after 3 tanks my mileage went up tp 24.5 mpg, all stock truck with 108000 kms.
  19. dobey

    dobey Member

    I see you're in Canada. Is that actually MPG or is it KmPG? Are you running your tires at 55 PSI? While a lighter 2WD truck with the 4.8 will get slightly better MPG than a heavier truck with a bigger V8, I don't buy that you're getting 24.5 MPG in pure city driving. My Honda that weighs about half as much and only has a 1.6L 4 cylinder, barely gets 26 MPG, driving mostly on roads that are 35-45 MPH speed limit. My Avalanche with a 5.3L with AFM and which I drive in 2WD only, also doesn't get anywhere near that. I'll buy the 24.5 KmPG though, as multiplying that times 0.6 gives 14.7 MPG, which is much more acceptable for a 2WD 4.8 Silverado LS.
  20. Parkrat

    Parkrat New Member

    Its 24.5 miles per imperal gallon or 20.4 miles per us gallon or 11.5 liters per 100 kms, and i run 38 psi front and 35 psi rear. I drive the truck weekends only, no rush hour so that helps a bit but its the additive that does it.
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