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Good Fuel Economy on K5???

Discussion in 'The Garage' started by Indyblazer, Jul 26, 2005.

  1. Indyblazer

    Indyblazer Registered Member

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    I drive an 84 K5 305 700R4 & 3.73 gears with 33x12.50 Mud & Snow tires. The tire noise at highway speed from the rolling resistance is deafening. My city/highway MPG is 8/11. I want better summer highway MPG. Are there any tires that have street/highway tread in a 33" size? I have replaced plugs, wires. distb cap and carb rebuild. All fuel economy ideas welcome!
     
  2. dyeager535

    dyeager535 1 ton status Premium Member

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    33x10.5R15 is IMO about the perfect size.

    BFG AT/KO's (and M/T's) are all I know of in that size.

    How's your driving style? My '83 K5 w/305/700/3.08/31's was at worst 10/15, at best 13/17.

    How about your speedometer/odometer? Since you have the "wrong" size tires, is your measure of distance traveled even close to accurate?
     
  3. cegusman

    cegusman 3/4 ton status

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    K5 and Fuel Economy in the same sentence:haha::haha::haha:
     
  4. seattle73k5

    seattle73k5 1/2 ton status

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    What he said hahahahahahaha!! :haha: :haha:
     
  5. google

    google 1/2 ton status

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    Well, if you just want economy, I would say go with a 31 10.5.
     
  6. highrlr

    highrlr 1/2 ton status

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    Ditto! These things are big heavy beast's with the arodynamic eficiancy of a brick, or a piece of plywood! On a side note though, I got 15mpg with my jimmy before the lift and tires, which was way more than I ever expected.
     
  7. cbbr

    cbbr 1 ton status GMOTM Winner

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    Yep. I would say that you need to buy whatever size fits a Honda Civic. Buy the civic also. :doah:
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    8-11 on a stock (even with slightly bigger tires) K5 shouldn't be acceptable to anyone. If I pulled down mileage that bad on my truck, when I know so many do better, then something's wrong that needs to be fixed.

    If that is the actual MPG, then somethings not right.

    There's a difference between expecting your K5 to get Prius-like economy, and knowing what it SHOULD be getting.

    Lack of economy means lack of efficiency which means lack of power. :)
     
  9. bluehen

    bluehen 1/2 ton status

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    I have a soft top on order that should be here sometime this week. I am hoping that the weight difference will help my fuel economy. That's definitely not why I bought it though.

    I drive an 87, so it's fuel injected. My last tank I managed 13.6 mpg. Not bad at all considering 350, 700R4, NP208 through 4.56's spinning 35x12.5.
     
  10. senatorwoodhouse

    senatorwoodhouse 1/2 ton status

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    Man that makes no sense!! I have an 81 305 th350 3.73 (not sure, I need to check) and 33's and I get ~13 city. What fuel are you running? I run premium. I tried regular and it dropped my economy down to 10 and lower. Also I am assuming that you changed your air filter? Exhaust? Is it free flowing? :D Also for road noise...is your undercarrige coated? I know that ziebart will steamclean and put protectant and sound deading material for ~$300. That is what Im going to do being in the rust belt and such. Do you have carpeting and door/side pannels? Hope that helps you at all
     
  11. trailblazr81

    trailblazr81 1/2 ton status

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    I think you need to make the motor more efficient. Like a K&N type re-usable hi-flow air cleaner, maybe an Edelbrock Performer intake, high flow exhaust, maybe some headers. Get the engine to breathe better. Youve got alot of wieght with the aerodynamics of a brick being pushed with what?? 150-160HP? For tires I would go with a BFG A/T or M/T. Both are good on highway. Your "stock" tire is a 235/75 or 31x10.50 so your engine is working harder to get the bigger heavier 33x12.50. Back in the day I had a 86 K5 with 305 and 700 with 4.56 gears and 35" tires. I got 12 MPG!! Woo-Hoo!!
     
  12. Cmoe

    Cmoe 1/2 ton status

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    put it on a diet..... I gained a mile or two without the top on....
     
  13. cbbr

    cbbr 1 ton status GMOTM Winner

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    Some of it depends on how you drive. If I stand on it, my Burb gets around 7-9 in town. I get around 14 hwy on a good day.
     
  14. ZooMad75

    ZooMad75 1/2 ton status Premium Member GMOTM Winner

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    Good fuel economy and K5 rarely go together. you can get better than you have, but it won't be what others consider "good".

    headers and dual exhaust (when legal for emissions) can help, but don't expect more than a 1 mpg gain (thats real optimistic). The tune up you did helps the most, but still won't net much gain unless you really had a problem before.

    You could drop your tire size down to 31's so you have less tire to turn, but your highway rpm at the same speed will go up. You could drop your axle ratio's down to 3.42's to drop your cruise rpm, but will act like a dog with 33's. You could do both and see a positive change to your mpg at a loss of ground clearance and crawl ratio.

    It is a total cause and effect type issue that effecs everything.

    Also, like Dyeager mentioned, is your speedo accurate with the 33's? the 33's vs stock size tires will slow the speedometer reading down. (this is due to the lower revolutions per mile the larger tire would have) If you base your mileage off of an inaccureate speedo, your mpg calculation will be skewed. Again, since the reading is slow, you would be putting a mileage figure less than acutal and thereby reducing your calculated mpg. To check speedo accuracy, break out a stop watch, hit a straight stretch of highway at 60 mph (as indicated on your speedo. Time yourself from one mile marker to the next. If your speedo is accurate the time it took to cover a mile should be 60 seconds on the nose. If it took more, your speedo is slow, less and it's fast. If it is off in either direction, you can't use the mileage from the odometer to come to an accurate reading of MPG.

    Bottom line, you might be getting better mileage than you think, you just don't have an accurate measure of how far you have driven between fill ups.
     
  15. sandawgk5

    sandawgk5 3/4 ton status

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    It sounds strange but try a whole tank in D instead of OD. With 3.73 and 33 you could be luggin the motor. Putting it in D will get it in more in the power band and in theory increase mileage. I have 31s with 3.08s and I got 12.5 from San Diego to Blythe through the desert and that was runnnin 70-75 and I had to cross a mountain pass per say on the San Diego county line.
     
  16. blazinzuk

    blazinzuk Buzzbox voodoo Premium Member GMOTM Winner

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    i never got good mileage with my blazer but just as a comparision my bro in law regurlarly pulls about 17 or 18 mpg out of a stock 87 suburban I personally think that you should be getting at least 14 out of it. Was the carb rebuilt and tuned or just rebuilt and by who. Wont do much good to rebuild a carb and not tune it. I have a freind who will tune quads and he can usaully get you 2 mpg more than you are getting also if the tranny is wearing out that can hurt your mileage make sure all your fluids are full and clean and make sure you don't have a broken hub or anything that is making the front end turn. And finally if you want to get better mileage slow down I know it sucks to do this but at 80 my blazer gets about 7 mpg at 65 it gets 10
     

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