Slant Six Fuel Mileage?

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Mike's Dart

Mike's Dart

Dodging The Negative Darting Toward The Positive
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McDermott, Ohio
I fueled up 45 miles back and the fuel gauge has dropped from "F" to 3/4 tank? The original owner's manual says this car has a 16 gallon tank, I guess that is correct? We installed a new sending unit 10 days ago and it just seems to be a bit hard on gas. I'll top off Saturday and see what the math says about the mpg on my /6 engine. It just seems like that gauge is moving south in a hurry? Checked for leaks at the new sending unit and it's still dry? Thanks in advance for your input!

Mike
 
Mike's Dart said:
I fueled up 45 miles back and the fuel gauge has dropped from "F" to 3/4 tank? The original owner's manual says this car has a 16 gallon tank, I guess that is correct? We installed a new sending unit 10 days ago and it just seems to be a bit hard on gas. I'll top off Saturday and see what the math says about the mpg on my /6 engine. It just seems like that gauge is moving south in a hurry? Checked for leaks at the new sending unit and it's still dry? Thanks in advance for your input!

Mike
Click to expand...
the only accurate way to determine miles per gallon is to divide the actual miles traveled by the gallons of fuel consumed. Be sure to determine the accuracy of the odometer,,,
Concerning slant six fuel mileage,, the slant was an economy motor back when the average full sized V8 car was betting 12 to 14 MPG. With a slant, depending upon the state of engine tune and the care given to the vehicle itself, front end alignment, proper air pressure in tires, brakes not dragging,how the car is driven, I would expect between 14 to 18 in town and high teens to low 20's on the highway. A slant built today for max economy could exceed that.
 
Mike's Dart said:
I fueled up 45 miles back and the fuel gauge has dropped from "F" to 3/4 tank? The original owner's manual says this car has a 16 gallon tank, I guess that is correct? We installed a new sending unit 10 days ago and it just seems to be a bit hard on gas. I'll top off Saturday and see what the math says about the mpg on my /6 engine. It just seems like that gauge is moving south in a hurry? Checked for leaks at the new sending unit and it's still dry? Thanks in advance for your input!

Mike
Click to expand...

You might not have a 16 gallon tank either.
My Dart was originally a 318 car and it has a 13.
If everything is correct and it does have a 13 you used a little over three gallons or so, and are getting about 14 miles to the gallon.

Just a quick non accurate guess from the info provided, and assuming it's a 13 gallon tank.
 
I use an iPhone app called Mileage Keeper to keep track of mileage. Every time you fill up, you enter the mileage and the amount of gas and it keeps track for you. (I get about 14 mpg in my stock 1974 /6 in town, more like 18 mpg if I do a lot of highway driving).
 
Hey thanks guys! I was really beginning to think I had a leak or something wrong with the new sending unit! My new fuel pump will be here tomorrow! Should be in the low to mid 60's on Monday! Odds are I'll go ahead and R&R the pump tomorrow though! I'll install another new fuel filter after the pump install as the fuel tank is clearing up nicely! Thanks again guys!!

Mike
 
Those new replacement sending units are off.....they read full when tank is full but go down faster than originals and read empty when there is still 5 gallon of gas in the car......As mentioned, best thing to do is math calculation to figure out MPG.....They also make a device that will correct the gauge measurements so they are accurate regardless what sending unit you have....see if I can find it...here is a good read

Solution to Fuel Gauge/Sender Problems
 
What Bbrroowwnn says... the new replacement senders are not designed for these tanks. They fit the opening, but do not incorporate the compensation in the scale for the fact that the spare tire well intrudes into the upper tank volume. They also have a shorter arm that pivots at a different point, that I suspect is more sensitive to splash. Even if you can adjust the F point and the E point (as suggested), they won't read accurately in the middle. In sum, they are better than nothing, but that's about it.
 
bbrroowwnn said:
Those new replacement sending units are off.....they read full when tank is full but go down faster than originals and read empty when there is still 5 gallon of gas in the car......As mentioned, best thing to do is math calculation to figure out MPG.....They also make a device that will correct the gauge measurements so they are accurate regardless what sending unit you have....see if I can find it...here is a good read

Solution to Fuel Gauge/Sender Problems
Click to expand...
Man, thanks so much! I thought I was nuts! I mean I am getting older and I was thinking "Did I fill up yesterday or maybe a couple days ago?" The gauge did not work when I bought it so I thought "Well maybe I just did not pay attention to it for a couple of days and I ran the gas down!" I mean, hell if I don't take the cardboard center out of the empty roll of paper towels down the hallway with me I'll end up in the laundry room doing laundry instead of getting a new roll of paper towels for the kitchen!! LOL! Thanks for the guidance on my fuel gauge reading problem!

Mike
 
Before I filled her up Monday the gauge read 1/4 tank. The pump kicked off after 6.6 gallons and the gauge read full? So the new sending unit is the culprit. At least it "kinda" works! :BangHead:
 
Mike's Dart said:
Before I filled her up Monday the gauge read 1/4 tank. The pump kicked off after 6.6 gallons and the gauge read full? So the new sending unit is the culprit. At least it "kinda" works! :BangHead:
Click to expand...

mine does the same thing.....those electronic boxes work to correct the problem.....The best ones are the ones you can program for 4 positions Empty 1/4 1/2 and Full......
 
Once I changed mine I just ran it out of gas and said "Hmm, so that's what it says when it runs out of gas"
Took the 2 gallon can out of the trunk and put that fuel in and went to a gas station.
Now I know.
 
They never were great on gas to begin with. Some people claim 30MPG blah blah blah but they are either lyin out their *** or measuring WRONG.
 
I agree with RRR. The slant is a dependable, long lasting engine- but in my experience a 318 uses less gas.
 
It all depends on the /6 and the configuration AND how, and how hard, you drive it. My family had 5 of them:
'68 Dart Auto: 20-21 mpg 65 mpg interstate
'72 Demon 3 speed: Maybe 1-2 MPG better than above
'73 Demon 3 speed: Same as above
'76 Dart Lite 3speed + OD and all the Lite version stuff: 29 mpg at 65 mph interstate
'80 Aspen Super 6 Auto with locking TC: 24 mpg interstate

Drive them at 75-80 MPH and the mileage drops like any other car. Drive them in urban or suburban stop and go traffic and the mileage drops. Nothing new here....

As for the fuel gauge the OP could get the gauge a bit closer at E by bending the float arm up.
 
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