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Got the Truck! Some questions!

Discussion in '1982-Present GM Diesel' started by Pookster, Feb 26, 2004.

  1. Pookster

    Pookster 1/2 ton status

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    I got my new truck. Needs a lot of TLC but the motor runs strong, tranny shifts good, and the brakes stop on a dime.

    For my previous questions, yes it is the 6.2 mated to the seperate bell housing, (NV4500)

    Added: 2 new batteries (walmart)
    Changed oil (Rotella 15w40)

    More TLC on the way. Needs new interior- needs new bed sides. Needs new paint!

    Question for you guys- I drove the truck home, without much trouble- but was a bit concerned with the fuel economy- I was getting about 16-18mpg over 100 miles- used about 5-6 gallons of fuel. I was expecting a tad bit more. Everything seems to be running pretty clean- I even added some of that diesel additive (the lube and stuff- added a little extra just in case the PO didnt). My cruise speed was around 1900RPM at 50mph (or abouts) in 5th.. And of course, the RPO codes in the glove box are non existant. Any ideas if this is optimal at going 70? (about 2300 RPM). I was feeling like a little larger tire would help my situation. /forums/images/graemlins/smile.gif
     
  2. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Ideal economy is 1800 rpm cruise. Canmore's 83 1/2 ton pick-up is very close to the ideal for economy and I know he has gotten 25 out of his on long freeway trips. His cruises at 1875 rpm

    I cruise at 2550 rpm at 65 and squeak out 15.8-16.1 mpg. the 15.8 is the worst I get in mixed driving, the 16.1 is continous freeway.

    With a 2300 rpm cruise rpm your mileage sounds about right, and with some larger tires you should pick-up 1 or 2 mpg. You can see that Canmore's truck gets about 9 mpg more than mine with a 675 rpm difference at cruise. 1 or 2 mpg of that is aerodynamic's and weight, the rest is rpm.

    Rene
     
  3. Pookster

    Pookster 1/2 ton status

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    Ok, the question is then... 33" or 35" tires? /forums/images/graemlins/smile.gif
     
  4. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    What gears and tires does it currently have?

    I'd say with IFS that 33's would give you less troubles, and if you have 3.73's would drop the cruise rpm's down to 1850 or so at 65 mph (~2000 at 65 with 4.10's)

    Rene
     
  5. Pookster

    Pookster 1/2 ton status

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    thanks!

    Of course, that would really mean 35" tires, since the true OD of most 35" tires are around 33.5-34".
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Actually, even though a 33" tire measures 'shorter' the circumference works out to be true. Measure the circumference and divide by 'pi' for the true diameter as it affects rpm.

    A 33" tire should have a circumference of ~103.6".

    Rene
     
  7. Pookster

    Pookster 1/2 ton status

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    Sorry, never did ask, why would 35's give me more trouble than 33's? The unsprung weight thing?

    [ QUOTE ]
    What gears and tires does it currently have?

    I'd say with IFS that 33's would give you less troubles, and if you have 3.73's would drop the cruise rpm's down to 1850 or so at 65 mph (~2000 at 65 with 4.10's)

    Rene

    [/ QUOTE ]
     
  8. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    IFS and big tires don't really mix well. It wears things out pretty quickly. There's also the fitment issue...33's you might be able to squeeze under there, whereas 35's you'll likely need to lift it some and maybe trim as well.

    Rene
     
  9. guard66s

    guard66s Registered Member

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    I have 35x12.50's with 3.73's and a 700r4, on street around SLC i get about 10-12 mpg but i have a heavy foot, on the highway i get 16 mpg, cruisin in 4th @ about 75mph, i get better mileage the first 600 miles after an oil change. p.s. anyone know why diesel is so F**kin expensive now? I can't afford 2.09 a gallon man, $60 + to fill up from E, im hatin it
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I gotta say that is pretty crappy mileage for a 6.2 and a 700R-4.

    I run 4.56's without overdrive and some heavy bias ply 40's and I manage 14.5-15.5 in town and as high as 16.5 on the freeway. My freeway rpm's are at 2600 or so.

    I'd expect your combo to net 20 mpg on the freeway...more if you slowed down a bit.

    Rene
     
  11. kennyw

    kennyw N9PHW Premium Member

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    I bet his speedo is off from the larger than stock tires and he is not correcting for the change in his gas mileage calculation /forums/images/graemlins/thinking.gif
     
  12. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    I bet his speedo is off from the larger than stock tires and he is not correcting for the change in his gas mileage calculation /forums/images/graemlins/thinking.gif

    [/ QUOTE ]

    I am sure that is the case.

    I don't have the 6.2l but a perkins and I usually get the opposite of you guys, I get 30MPG around town when it's mostly off idle, and drops to 20MPG on highways.
    I guess either my injectors are dumping at low pressures or the Turbo is making the difference.
    I noticed after I fixed the leak in the tirbo ducting it started to smoke black when i get heavy on the skinny, before that it was getting better mileage but less power. /forums/images/graemlins/dunno.gif
    Still I guess I can't complain about 20MPG for the worst case scenario /forums/images/graemlins/woot.gif
     
  13. HD

    HD 1/2 ton status

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    [ QUOTE ]
    p.s. anyone know why diesel is so F**kin expensive now? I can't afford 2.09 a gallon man, $60 + to fill up from E, im hatin it

    [/ QUOTE ]
    It must be nice to only pay $2.09, it's $2.45 in Ridgecrest, CA /forums/images/graemlins/yikes.gif
     
  14. DukeBoy88

    DukeBoy88 1/2 ton status

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    Ouch!
    I won't complain about $1.73 anymore then.
    why the big difference? taxes?
     
  15. imiceman44

    imiceman44 1 ton status

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    [ QUOTE ]
    Ouch!
    I won't complain about $1.73 anymore then.
    why the big difference? taxes?

    [/ QUOTE ]

    Yep Taxes, here it's 2.65 for Diesel #2 and 2.45 for premium gas, what's up with that, It used to be diesel was cheaper than regular gas.
    /forums/images/graemlins/doah.gif
     
  16. guard66s

    guard66s Registered Member

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    thats comped man, i made up for the tires, 2.43 a gallon? oh man i thought i had it bad
     
  17. arveetek

    arveetek 1/2 ton status

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    [ QUOTE ]
    It used to be diesel was cheaper than regular gas.
    /forums/images/graemlins/doah.gif

    [/ QUOTE ]

    Diesel is still cheaper in Southwest Missouri. Gasoline is hovering near $1.95 while diesel is about $1.60. I paid $1.58 Monday night at the Flying J! /forums/images/graemlins/laugh.gif

    Sheesh! It's awful when you start thinking about how $1.58 is cheap for diesel fuel! /forums/images/graemlins/eek.gif It was just a few years ago that I remember filling up my dad's diesel pickup at $.89 cents a gallon!

    Casey
     
  18. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Gasoline here is 99.9 cents per liter...or $2.70 USD per US gallon.

    Diesel is still under 80 cents a liter most places ($2.16/US gallon)

    A full tank still lasts me almost 3 weeks so it hasn't hurt my wallet any yet.

    Rene
     
  19. SS66

    SS66 1/2 ton status

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    Regular unleaded was $2.10 as of lastnight. There is a little sticker on the pump showing the breakdown on how much the state taxes each gallon. According to that sticker they were charging 50 cents worth of taxes back when gas was in the $1.80's. Yes boys and girls, thats over 1/4 of the total price for one gallon. So now they are probably getting around 60 cents per gallon. /forums/images/graemlins/angryfire.gif /forums/images/graemlins/angryfire.gif

    How are the taxes up there in Canada on gas?
     
  20. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    They have the tax versus cost of fuel stickers here too (at some stations) Last I recall it was approx 42% tax...and it's a percentage so the amount per liter has increased as the prices have gone up. On top of the taxes are local levies for transit subsidy, another 8 cents a liter. For quick reference my truck averages just under 100 liters for a fill. Every cent per liter at the pump costs me another buck to fill it up.

    Fortunately a very good friend of mine lives just outside the area affected by the transit levy, so when I go see him I fill up out there.

    Rene
     

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