Fuel Mileage issues on my 86 C10

[sabes14jeff]

This is my fully restored 1986 c-10
here are pictures and some info on it
350 5.7L w/ 6,500 miles (crate motor)
4-Barrel carb (restored)
th400 (restored)
Dakota Digital Gauges
Dual exhaust 3"
17" wheels
Custom sound system w/ 2 10" pioneer subs
NO RUST

http://s682.photobucket.com/albums/vv187/sabes14jeff/?albumview=grid

any comments would be greatly appreciated


I live in Frederick, MD

[nucknoel89]

Did you forget your password for your old account?  It appears you used to be JJSZABO, cause that's the exact truck he built.  I thought you gave that truck to your son....

[sabes14jeff]

i am the son. me and my dad keep talking about it and the 12 mpg just ain't cuttin it anymore. right now I'm thinking about going to diesel.

[choptop]

by the time you pay for the deisel truck, you could have bought alot of gas for this one. It would be cheaper to upgrade to Fuel injection. You figure 12 mpg, is that compensating for the different tire and wheel size. I ask, because alot of people are getting better mileage than they think, but are calculating it wrong because the odometer is off due to tire size.

[sabes14jeff]

is there any way that i can see if it really is off? i do have 17" wheels on it and i thought it might affect my speedometer but not the odometer. how much would it cost to put fuel injection in it?

[DnStClr]

There are speed calculators like the one on 4lo.com that can help you determine your percentage errors.
http://www.4lo.com/

Any time you add bigger tires there is more friction to overcome, so the engine works harder and uses more gas just to get up to cruisin speed. Higher vacuum in the engine causes more gas to sucked into the carb. To compensate, a different gear ratio needs to be installed in the dif case. If you're running a 3.08 ratio you may have to change to a 3.42. It would be more efficient at getting the truck up to speed without overtaxing the engine- so you would be in the power band quicker and using less gas. The calculator on the web site can help get ya the right dif ratio.
It's also possible that the speedometer is off- well, I forgot-it's electronic. Should be ok.
The 3 speed tranny is hurting your gas mileage too. Buying and installing a 700R4 overdrive tranny would be cheaper than swapping over to tbi.

[eventhorizon66]

Find an 87-92 1/2 ton and pull the complete TBI system and 700R4.  Then you'll be in the 18-20 mpg zone (if driven conservatively).  But I think a 700R4 alone will put you in the 15-17 range with a properly tuned Q-jet.  What gears do you have in the rear?  3.42's behind a 700R4 would be perfect for gas mileage.

[Captkaos]

Think of it this way, it is paid for, and you only have insurance and gas plus what ever maintenance for cost.
getting a car with better mileage would require getting something that hasn't been "restored" to new and bought outright, so you are buying someone elses problems...

Switching to TBI and 700R4 will probably get your mileage up to about 15/20 on a 2WD.

If you want to test you speedo, get a car with known correct speedo have them go 60-65 and follow them.

What size are the tires are on the truck?

[dumbucket1]

Or drive your truck with a gps that shows your mph

[choptop]

Here's the way I look at it. My 01 Crewcab dually with the 8.1 gets 10-12mpg. Lets say I average 10mpg. If I drove 500 miles a week ( I do just not in this one) that would be about $150 a week in fuel if it was $3.00 a gallon. In 4 weeks thats $600,  or $750 in a 5 week month. And about $50 for insurance. So $800 total.First thought is holy cow, thats a truck payment.... No
  My daily is an 08 that does do about 500 miles a week, but gets about 18MPG. Thats a little over 27 gallons @ $3.00 gallon which is $83.33 a week or $416 for 5 weeks. wow, looks like I saved $333 a month driving a new, better efficient truck.  Look again. I have to ad $510 for truck payment, $200 or so for insurance, so that makes my total $1126 for a month. The 18 isnt even an accurate number because its not always that good. Its usually around 16.5mpg. I took the worst of one and added the best to the other.
So, it costs me $326 more per month to drive the fuel efficient one that the 10 mpg gass guzzler.
   That said, I have the smaller one because it fits my job better, plus I can use it as a tax right off. ( well at least for now)

  I also figured the cost of deisel versus gas when I bought my last truck. I would have to drive the deisel to 225,000 miles (with no major repairs) if the deisel got 20MPG, versus the gas to 100,000 miles at 15mpg just for them to equal eachother out in the initial purchase price and extra maintenance cost for the deisel. If you pull large loads daily, then the deisel is worth it, if its just a daily driver, I dont see the benefit. The numbers dont add. I showed to numbers to my business partner who has run a 1 ton deisel for the last 10 years. This year he bought a 1 ton gas truck, and mid through the year he has figured the gas cost him about 35% less to run than his deisel, which he said never got better than 15mpg versus the gas at 13mpg. Same job being done, just different truck.

[Lt.Del]

Drive her on the interstate...you know, you can see the yardsticks (I mean mile markers) and look at your odometer.  If it takes .8 miles to go b/w two yardsticks, ummm, your speedo gears needs adjustment.  You're actually going 20% more miles than what you think according to the odo.
If it takes 1.2 miles to go b/w yardsticks, well, you're not going as many miles as your odo says.

That'll give you an idea if you don't have a GPS or, as Chris says, a partner to run next to you.

You can always do the second hand on your watch.  If it takes 60 seconds to go b/w yardsticks, well, that's 60 miles in 60 minutes....60 mph...see what your speedo says then.

[VileZambonie]

It must be the custom sound system. I'd bet money on it. 

[Lt.Del]

Custom sound system w/ 2 10" pioneer subs

It must be the custom sound system. I'd bet money on it. 

lol
especially if you have a lot of heavy metal CD's          

[TexasRed]

How hard would it be to go to smaller wheels and tires? That might give you a boost in mileage right there and you could prolly get the wheels in a junkyard. They wouldn't be show wheels but it may save ya some scratch in the end.

[eventhorizon66]

Custom sound system w/ 2 10" pioneer subs

It must be the custom sound system. I'd bet money on it. 

lol
especially if you have a lot of heavy metal CD's          

It's funny you mention heavy metal.  I swear if my transmission ever lets go it will be while "Raining Blood" is blaring on the stereo.  Man that song kills my mpg.