Miles per gallon?

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just checked my mileage this morning during a fuel stop

19.3 MPG

Slant six/ OD 833 and 2.76 open in a dart body.

I do have to confess ....this is mostly highway.
 
kyler said:
Hello,

I have a 1966 Valiant 200 with a slant-6 225, 1 barrel carb, and 3-speed automatic transmission. What kind of mileage should I be getting? When I bought the car, I was under the impression it would be somewhere around 18-22 for an average. As it is, I have been calculating 10-11. Why am I getting such poor mileage? It just doesn't make sense to me.
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What slantys can do, and what they do, do...........Your results may vary
They can do excellent on the prairies or at a somewhat constant elevation. Washington has some pretty big elevation changes. Hills take the slanty out of it's comfort zone.One can tune the cruise circuit pretty lean. but if you don't or can't stay in it,then there is no point. An EFI vehicle, on the other hand, has a computer that can do a whole lotta calculations per second, and has a feedback loop, that tries to keep the F/A ratio just right, elevation changes and all.
 
When I was daily driving my 65 with a 200K+ mile 225 and worn out everything else I regularly got 18 city 22 hwy (and that was 65-70mph). As others have suggested, make sure your vacuum advance works, make sure your float level is set to something reasonable, and set the ignition timing to 12-15 BTDC.

If you're getting less than 15mpg, something is out of whack.
 
In 1978, I bought a '71 Dodge Dart Custom with a 225, auto, power steering and 2.73 rear end. I was the second owner. The car never got more the 17mpg. I know because I had a job that paid mileage so I needed to keep meticulous records.

You need to keep things in perspective. At that time the big blocks would get around 9 mpg, the small blocks would be getting around 14 to 15 mpg. The used car lots were full of "gas guzzlers" and everybody was buying "economy cars". Gas had doubled in price within a 6 month period and nobody wanted a "muscle car".

By the way, an "economy cars" would get around 17 to 25 mpg and everybody were loving those '60s six cylinder cars that got "excellent" gas mileage. And the myth continues. They weren't' all that gas efficient, they were only "economical" when compared to their contemporaries. Now if you want "economy", buy a new 4 cylinder, front wheel drive car.
 
I made sure that my choke and everything are working properly, changed my thermostat, and did a few other things before recalculating my mileage.

I am not at a comfortable 15mpg, and that is ONLY city driving. There is a short "highway" mixed in there, but it's about 6 miles at 45-50 mph the whole time. So, I am happy. It is worth the small extra cost (when compared to my 18 mpg Subaru in city) to get to drive such a great car :)
 
That sounds better, and more reasonable. "City" driving can certainly knock things down.
 
67Dart273 said:
That sounds better, and more reasonable. "City" driving can certainly knock things down.
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Yes, exactly. Any time the car is at a stop light, it is just burning fuel. Might as well measure in gallons per minute. Acceleration from stops uses more fuel than cruising or coasting too, but that's at least more consistant. It's the difference in time not moving that generally makes "city" is so hard to compare.

When you get a chance, check if the distributor has ever been changed. Replacement distributors were (are) somewhat generic. So the only way to see if the curve is in spec for your particular engine, year and options is to test and tweak if needed. It runs good, so its probably close, but if you're up to it, checking both the mechanical and vacuum advance is a good place to look for milage.

To add my /6 milage experiences to benchmarks here. Stock smogged '75 Valiant w/ 904 commuting from '83 to '88 it regularly averaged a bit over 17 mpg in mixed/city. A rather loose '68 Barracuda got well over 21 mpg on the highway when I brought home. Engine (with points) was really responsive compared to the smogged and heavier '75 Valiant even with electronic ignition. Too bad it spun a rod bearing on the way to work a month later...
 
kyler said:
I made sure that my choke and everything are working properly, changed my thermostat, and did a few other things before recalculating my mileage.

I am not at a comfortable 15mpg, and that is ONLY city driving. There is a short "highway" mixed in there, but it's about 6 miles at 45-50 mph the whole time. So, I am happy. It is worth the small extra cost (when compared to my 18 mpg Subaru in city) to get to drive such a great car :)
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When I decided to get my Dart and sell my Saturn, gas was still slightly over $3 a gallon. I did the math based on the amount of driving I did each year, the difference in gas mileage between the two vehicles, and the cost of gas. Even with a conservative worse case scenario estimate of the Darts fuel mileage and assuming gas prices will rise again, it still only came out to a few hundred bucks a year. Some folks spend that on smokes or coffee. I'll spend it on gas with a smile on my face O:)
 
Your car has a problem. I don't care how much city driving vs. highway driving you do. It's not normal for a slant six to be getting 10-11mpg unless you're flooring it from every stop.

My guess is that you have a remanufactured carb on there. Back in the day I was getting 10mpg with a remanned carb. Put a NOS carb on and it jumped to 15-16mpg. Did other modifications and now I'm up to a consistent 20mpg in the summer and no worse than 17mpg in the winter. I do more highway driving than you, but even on the weeks that I'm in stop and go more often, it still doesn't dip down much.
 
kyler said:
I made sure that my choke and everything are working properly, changed my thermostat, and did a few other things before recalculating my mileage.

I am not at a comfortable 15mpg, and that is ONLY city driving. There is a short "highway" mixed in there, but it's about 6 miles at 45-50 mph the whole time. So, I am happy. It is worth the small extra cost (when compared to my 18 mpg Subaru in city) to get to drive such a great car :)
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ESP47 said:
Your car has a problem. I don't care how much city driving vs. highway driving you do. It's not normal for a slant six to be getting 10-11mpg unless you're flooring it from every stop.

My guess is that you have a remanufactured carb on there. Back in the day I was getting 10mpg with a remanned carb. Put a NOS carb on and it jumped to 15-16mpg. Did other modifications and now I'm up to a consistent 20mpg in the summer and no worse than 17mpg in the winter. I do more highway driving than you, but even on the weeks that I'm in stop and go more often, it still doesn't dip down much.
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I don't think you caught the last post by the OP................
 
This is why I swapped out for a v8.. Same mileage, 3x the power and better sounds.
 
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