Fuel Mileage

Discussion in 'General Automotive Tech' started by marcf3998, Dec 10, 2011.

  1. marcf3998

    marcf3998 Active Member

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    ***Warning this is a boring thread, science is like that***

    I recently bought a 1982 Oldsmobile Custom Cruiser with 110600 miles on it. It had been sitting for a while and has only had ~10k put on it in the last 10 years. There was a receipt for the tires and radiator in the glove box with mileage. (note, I replaced the 11 year old tires for safety, after 6 years they are dangerous)

    So I am going to list what I have done so far and the mpg at that point. And I driving to Manchester TN from just East of Kansas City, MO next week. I plan to test a few things knowing the route, see if I can get better mileage. I know ethanol gas sucks and certain places have straight gas, driving conditions, etc, things like that.

    I also am testing right now the mileage of an engine that is running at the right temp. My theremostat was stuck slightly open and the engine never warmed up. My theory is it ran rich, choke partly engaged, reducing mileage. I know it runs better now, no stumbling and the heat is very welcome :) (18 degrees out this morning).

    So far here is what I have done and the mileage etc...

    Mileage Gallons Miles MPG
    10600
    10724 16.00 124.00 7.75 Trans fluid/filter, pretreated with Seafoam
    10979 16.65 255.00 15.32 Oil change, tires, tie rod end
    11217 15.95 238.00 14.92 Shouldnt have thromped it, repeatedly...
    11485 17.26 268.00 15.53 Changed Thermostat, heatercore

    *A final note, this car is stock, the only thing its missing is the air cleaner hose to the radiator mount. I havent tinkered with it, yet.
     
  2. marcf3998

    marcf3998 Active Member

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    I got better mileage this tank AND I idled to warm it up. I filled the tank today added Marvel Mystery Oil and changed the plugs and wires.

    This should be an interesting tank full. The plugs were old, worn out to about .120. The wires came apart and appear to be factory, or very old. The rotor and cap are worn, I cleaned and polished them until I can get a new set. The crud I removed would have definately hurt spark quality. It idles very smoothly now. :yup:

    Mileage Gallons Miles MPG
    11485 17.26 268.00 15.53
    11730 15.06 245.00 16.26 Added Marvel Mystery Oil, changed plugs and wires.

    Note to moderator -- if you can move this thread to the mileage section please do so, I was jumping around and thought I started it there:banghead3:

    Sorry
     
  3. wagonman76

    wagonman76 Well-Known Member

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    Good things so far. A stuck open thermostat will hurt mileage. As will bad plugs and wires.

    I don't know if this car uses an oxygen sensor, but if it does, it might be a good idea to check that out. They get coated over time and tell the ECM to feed it a richer mixture than it really needs.

    But I would like to hear what others are getting for MPG with a similar car. I think yours seems to be about right.
     
  4. marcf3998

    marcf3998 Active Member

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    OK,so I made it to TN with very little drama. Rain coming in and broken motor mount were minor things...:eek: I will add pics and another thread to explain those tomorrow morning.

    The first mileage was mixed local and highway. Second was mostly highway and the last was all highway. My top speed was 76 according to the gps (down hill most likely). I mostly just drove though.

    Marvel Mystery Oil was in the first tank, but I didnt add it later on.

    Miles Gallons MPG
    245 15.06 16.27
    209 11.58 18.05
    305 15.01 20.32
     
  5. ross

    ross Well-Known Member

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    A car this old undoubtedly has some dried up gaskets in the carb. You could remove the carb and just tighten a few screws or dis-assemble it and replace all the gaskets.
    Look into the carb with the engine running and watch for any dripping from the venturis. Any drips means the carb needs work.
    Fresh plugs and wires and properly tuned carb is about all you can do.
     
  6. marcf3998

    marcf3998 Active Member

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    Ross do you think that I should be getting better mileage? I have noticed other people with this wagon mention 20 PLUS mpg so I wondered. :confused:

    I liked Rochester carbs when I used to rebuild them, this one is the Computer Control Command type. I havent built one like it before but it cant be too different.

    I am considering a non CCC Rochester and a simple HEI without the computer controls. (but I'm broke right now :mad: )
     
  7. snooterbuckets

    snooterbuckets Well-Known Member

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    Does it have a 3 spd or 4 spd auto? I'm thinking probably the 3spd. Maybe with the 4spd auto, you might approach 20mpg.
     
  8. marcf3998

    marcf3998 Active Member

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    @snooter, 4 spd the 200-4r.

    Ok well I made it back from TN to MO in one shot, and I pushed the old girl a bit. 78.6 mph according to the GPS. :character0182:

    Luckily that was in a 70 without the Trooper noticing. Of course I didnt notice either at first, she rides smooth. :cool: Anyway mileage reportss:

    Miles Gal's MPG
    237 12.19 19.44
    225 11.66 19.30

    Miles Gal's MPG
    284 13.66 20.79 <<< this gas is no ethonal, I drove about the same on all but got slightly better here even though it was my fastest avr. speeds. :thumbs2: So is the much stated rumor about ethonal lowering your mpg true? (personally, I think so)
     
  9. lowlow37

    lowlow37 Well-Known Member

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    This winter we have a mix of 10% ethanol in the gas..... I get about 22mpg with my TBI -700r4 conversion, mixed city - highway.. I think your numbers are totally accepteble with a carb setup...
     
  10. ModelT1

    ModelT1 Still Lost in the 50's

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    I did not heed your warning. Yes, I did find it boring but enjoyed it! As comparison, Florida, 60s-70s town and country mixed, 10% ethanol, Dodge quadcab with topper, Hemi with fancy electronic crap: 14 MPG!!!!!:banghead3:-------Last we drove the 55 Chevy wagon with 305, 2004R we got around 19-20MPG. Same 87 octain corn crap for fuel.(y)
     
  11. jmt455

    jmt455 Well-Known Member

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    I think 20 mpg in an OCC is very respectable.
    If you can afford it, true duals will help.

    I chose to have my Rochester CCC Q-jet rebuilt by a pro because I have never rebuilt one of the computer-controlled carbs. When I priced out the rebuild kit plus the mixture control solenoid and a TPS sensor, the rebuild charge didn't seem so bad. But it was still about $300...ouch.

    I think it's a good idea to replace the O2 sensor. My experience with my Bonneville has been much the same story as your OCC. I had a bad thermostat (stuck wide open), weepy carb gaskets, badly fouled plugs. It's running MUCH better after taking care of those items, but it's still running very rich. I haven't changed the O2 sensor yet; that's next on my list, too.
     
  12. ModelT1

    ModelT1 Still Lost in the 50's

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    About dual exhaust. I put duals on everything. Even the Dodge truck. Only difference I've ever noticed is the cool sound with glasspacs. :clap: The difference in fuel savings will never be made up.
    I know, many will argue. :slap: Maybe it's because with duals I tend to mash the gas more to listen to the music !:rofl2:
     
  13. jmt455

    jmt455 Well-Known Member

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    CatModelT wrote: "Maybe it's because with duals I tend to mash the gas more to listen to the music !"

    Yep, that would be me, too! :yup:
     
  14. lowlow37

    lowlow37 Well-Known Member

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    Amen to tha brother!!
    Sux for me on the Estate that since i put the air in the rear, duals wont fit.. But a beefy 3" no mufflers do the job just fine:evilsmile:
     
  15. ModelT1

    ModelT1 Still Lost in the 50's

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    :dance:That's got to be awfully loud !
     

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