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what are your MPG's?


imusa76
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This weekend we went took a long ride with the car, 207 miles. and I was amazed at the MPG's I got.

 

I topped off the tank when we left, and I topped off when we got back, 9.5gal and traveled 207 miles, that comes out to almost 21+ MPG's!!! 98% highway.

 

Stock 302, Stock 2100 Carburetor, Stock FMX trans, and Stock 2.79 Rear end, Dual Exhaust.

Iyman

1972 Mustang Convertable :run_horse:  [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=1507]Visit My Garage[/button]

Visit the Mustang Car Club of New England Facebook Page [button=https://www.facebook.com/MUSTANGCCNE]MCCNE FB Page[/button]

 

Visit the Mustang Car Club of New England Web Page [button=http://www.mccne.com/]MCCNE Web Page[/button]

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Show off. :P Good job though! What speed were you going on the highway?

 

Seems like I get between 9 - 12mpg but I've not been easy on the throttle after the engine is warmed up. I should do a Myth Busters experiment. ;) I've not driven it much at all this year though. :-/

 

I keep track of my mileage at http://www.fuelly.com/car/ford/mustang. My 4-speed car is the only 71 in the group. It would be cool to see others on here track on fuelly then we could see what the real world mpgs look like.

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90 of the miles were at about 50 MPH, and the Rest was at about 65 - 70MPH.

Iyman

1972 Mustang Convertable :run_horse:  [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=1507]Visit My Garage[/button]

Visit the Mustang Car Club of New England Facebook Page [button=https://www.facebook.com/MUSTANGCCNE]MCCNE FB Page[/button]

 

Visit the Mustang Car Club of New England Web Page [button=http://www.mccne.com/]MCCNE Web Page[/button]

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i've gotten 25 mpg highway on a long trip as well. at the time i had a taller ratio 2.75:1 this was on my 351 cleveland also.

 

what murders MPG is the accelerator pump/power valve, that is why a light pedal slow acceleration increases MPG. When you stomp on it 30cc of fluid goes right into the engine instantly. additionally the Power valve will open and dump like 1/2 a gallon into the engine. Plus the cruise jets are running and the transition slot is driping fuel.

 

so every time you get on the pedal, first your dumping pump shot into the engine from the accelerator pump to compensate for lean condition, the engine vacuum then drops and the power valve kicks on, so 3/8 or 5/8 tube worth of fuel is dumping into the engine for as long as you hold the pedal down. plus the cruise jets are flowing down into the engine. that is why for street driving red light to red light you get like 4-12 mpgs even modern cars can get like 6-9mpg. It was a joke on some cars that you reved the motor and watched the fuel gauge drop 1/8 at a time, and that was actually true on the 1970s jeep cherokee where in offroad configuration you got 1-2 mpg and 4-6 on the highway, the dodge power wagon was just as bad also.

 

most guys want more power so they also increase the carb CFM and increase the exhaust size, flow more in, flow more out equals more power and drop the MPG even more. that is in addition to what Cubic inch the engine is.

there is more to it also the heads on the engine and intake valve to exhaust valve size ratio has a tremendous effect on MPG. i read somewhere the closer you get to IN/out valve ratio being 1:1 the better the mpg.

 

this is why in the fuel crises days the Inline 6 was the best option for 71-73, coupled with a single pipe exhaust and 2 barrel carb and the tallest 2.75:1 ratio you could find, and it was possible to get 35MPG in a 71-73 mustang on the highway. and street mpg would be in the 9-12 range, some people would advance the timing and increase throttle rpms and could even get 16mpg on the street with a light foot and learning how to roll the car with a higher idle.

 

This is why the vacuum advance is so critical and it is the least understood part of the motor for many many engine builders. they all think those are evil and they always disable them and run the engines on mechanical advance only.

basically the vacuum advance advances timing depending on load in addition to the mechanical advance. that means as you accelerate the load is increased the vaccum advance advances timing which raises engine RPMS and gets you to your desired Speed faster meaning your lighter on the pedal without you realizing it. it also helps the motor burn the fuel better by adjusting when spark occurs. so the engine runs more efficiently. just tuning a distributor for the street could bump MPG 10 or more.

 

so lean out the motors just shy of detonation install a smaller diameter exhaust instead of 3" or 2.5" you go to 2.25" and the increased back pressure and carb double dip from resonance will increase MPG by itself. but the seat of your pants may feel slower.

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Hmmm. 35 MPG You are sure making a good case for the inline 6 for cruisin!

 

Ray

1971 Boss 351  

1972 Q code 4 speed convertible 

1971 Mustang Sportsroof  351-2V FMX 

1971 Hardtop (parts car)

1973 Mach 1 (parts car)

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Even though I've greatly increased the power output of my 351C, I'm thinking the AOD and 3.00:1 rear gears should offer up some pretty decent fuel mileage numbers - providing I can keep my foot out of it, that is. My speculatory 'fuzzy math' has me in the 21-22mpg range based on 'normal' driving.

 

I know my 1997 Dodge Ram 1500 4x4 gets an average of 12mpg during 'normal' driving for me (a mix of 1/3 regular street driving with about 2/3 'freeway' driving). So if I can squeeze out over 20mpg during 'normal' driving conditions, it'll be close to double my overall fuel economy.

 

I also expect to improve it even further after awhile by installing an Edelbrock E-Street TBI set-up. But, that's down the road - gotta get it 'on the road' first. ;) :D

Eric

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Even though I've greatly increased the power output of my 351C, I'm thinking the AOD and 3.00:1 rear gears should offer up some pretty decent fuel mileage numbers - providing I can keep my foot out of it, that is. My speculatory 'fuzzy math' has me in the 21-22mpg range based on 'normal' driving.

 

 

I think you're in the ballpark Eric. With a 26" tire height you'll be at 1800 rpm at 70 mph - a great rpm for mpg. The downside is the AOD's 2.40 first gear might be a tad slow off the line with a 3.00:1 rear but you'll be able to hit 65mph in first gear at 6k rpm. :D A normal 2500 rpm shift point would be 27mph from first gear and 44mph from second to third gear.

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I think you're in the ballpark Eric. With a 26" tire height you'll be at 1800 rpm at 70 mph - a great rpm for mpg. The downside is the AOD's 2.40 first gear might be a tad slow off the line with a 3.00:1 rear but you'll be able to hit 65mph in first gear at 6k rpm. :D A normal 2500 rpm shift point would be 27mph from first gear and 44mph from second to third gear.

 

Then that would be the downside of the FMX as well, since the AOD and FMX share the same gear ratios... until the AOD kicks into Overdrive (which the FMX does not have). ;)

 

That's one reason I haven't been so worried about changing out the rear gears - the car essentially came this way from the factory (minus the Overdrive, though). Factory 245hp 351C-2V 'H-code,' FMX, 3.00 seemed to be 'OK' out of the box... I'm thinking it should be pretty awesome with 400-ish horsepower. :D

 

Worse-case scenario: I swap the 3.00s for 3.55s.

 

 

Sorry for 'jacking the thread... but at least it's relevant. :cool:

Eric

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With my 460 ,i figured it would be too depressing to even try to figure that out!:P

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460 , Edelbrock Performer carb. + intake , 204 / 214 cam , Pertronix Flamethrower 2 billet dizzy + coil , Crites long tubes , C6 .

 

 

 

 

 

 

 

 

 

 

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With my 460 ,i figured it would be too depressing to even try to figure that out!:P

 

If you have anything close to highway gears (3.55 or taller), it might not be as bad as you think. :cool:

Eric

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When I first got my car I remember not getting any better than 12MPG with a 3.25 rear. Sort of curious as to what the numbers will be once I get it on the road again.

-jbojo

-john

(jbojo)

351C 4V cc heads, 10.5 : 1 CR, 290 Herbert cam, Flat top forged pistons, forged connecting rods, Atomic efi,

C6 with Gear Vendor overdrive, 3.89 Tru Trac, Hooker Super Comp with 2 1/2" Pypes Exhaust.        

 

Some Mod pictures can be seen at: [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=2026]Bojo's Garage[/button]

 

 

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I haven't done the math but my rought estimate is 11.7 and thats exactly the way it seems too.

 

302 4bbl 3spd manual 3.00 rear - 55mph some minor stop n go.

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I get roughly 5 to 6 mpg in city and close to 10 to 12 highway with a 2.75 open rear

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Yea,Tho i cruise through the valley of the shadow of rice,I will fear no Turbo,For Torque art with me.Thy rods and crankshaft,they comfort me. :D Robert [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=357]Visit My Garage[/button]

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I'm telling ya...we all (those who are interested in this topic) should get on FUELLY.COM so we can track it much better.

 

Mine is off because I had a leaking gas tank & didn't know it. Fixed now so I need to put some miles on it to see what my real mileage is. Below is my fuelly stat that automatically updates every time I fill up.

 

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Last summer I-10 Florida to Houston & back @ typical interstate 70-75.

I was actually dissappointed to only get 20MPG.

308/4R70W/3.25

Miss May, 65 2+2 EFI 331 4R70W 3.55 trac-loc Not much origional remaining

Robert's 73 Vert 308 4R70W 3.25 trac-loc. EFI conversion & 8.8 Trac-Loc 3.31 started.

 

 

If it ain't broke, I haven't modified it yet.

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When I first got my car I remember not getting any better than 12MPG with a 3.25 rear. Sort of curious as to what the numbers will be once I get it on the road again.

-jbojo

 

That's about what I was getting with the original Autolite 4300D on it, switched to a Edlebrock Thunder Series, performance and MPG increased...but I suspect a lot of that had to do with the leaky Autolite (even after having it rebuilt for $400.00). It now sits on a shelve looking down upon the Mustang.

 

Jim

Jim

 

M code 71 Mach 1, 351 4V Cleveland, Ram Air (not factory), C6 Trans, 3.5 rear

 

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Last summer I-10 Florida to Houston & back @ typical interstate 70-75.

I was actually dissappointed to only get 20MPG.

308/4R70W/3.25

 

Not a bad combo. I think 3.50 gears would be optimum with 26" tires. ;)

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You want good gas mileage, go buy a priuis.

 

Had one. Sold it. I think you're missing the point. For me anyway, I want to maximize the efficiency potential of my 351c 4v. It's not about getting 40 mpg. I drive 3000 - 4000 miles any given month and if anyone could justify a prius I think I could. I spend a lot on gas any, ANY, savings I can capture because a state of high tune during the leisurly times in my mach 1 then all the better plus a performance boost for my not so gentle times.

 

It's about a high state of tune in a fun car with a goal of not "good" mileage but good mileage for our cars.

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I don't think there's anybody out there who would honestly buy a classic Mustang for its fuel mileage.

 

But there is certainly nothing wrong with sharing ideas about how to get the best fuel mileage as possible out of the ones we have.

Eric

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I don't think there's anybody out there who would honestly buy a classic Mustang for its fuel mileage.

 

But there is certainly nothing wrong with sharing ideas about how to get the best fuel mileage as possible out of the ones we have.

 

Exactly my thoughts Eric.

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When I bought my car and could buy leaded gas it got right around 19-20 on the highway, a bit less overall. Stock 2V 351c.

 

The communist plot to take over America of unleaded gas decreased that to 15-17 overallbut mostly highway miles. Highway only trips were about 18-19 at best. It once ran out of gas an all highway miles at 310 miles. On leaded gas I could get 360 mile range easy.

 

Two years ago I swaped the 3 speed to a t5. It now gets an average of 22-23. On an almost all hiway mile trip a couple weeks ago my calculations showed it got 28. Never done that before adn still think something was not right.

 

My original calcualtions with putting the T5 in I figurred it would average 26-27 on the higway. Although when it did not a friend of mine siad the engine was not running at its maximum torque efficiency at the slower revs and was not surprised. He know more about this kind of stuff so I do not know if he is 100% right here or not.

 

It does about 1500 revs at 55 MPH and about 1900 at 70.

 

It gets better gas mileage than either of my other two vehicles! But I am still looking for ways to possible tweak it upwards.

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I don't think there's anybody out there who would honestly buy a classic Mustang for its fuel mileage.

 

But there is certainly nothing wrong with sharing ideas about how to get the best fuel mileage as possible out of the ones we have.

 

Exactly my thoughts Eric.

 

its kind of what I was thinking with this topic.

I like the FUELLY.COM Idea to track our mileage.

 

as for the Prius, we have a 2010 we average 45-55 MPG, my wire does 450-500 miles per week so I was able to justify it.

My mother went and bought one the following year a 2011 and with her driving habits she gets 60+ MPG..

Iyman

1972 Mustang Convertable :run_horse:  [button=http://www.7173mustangs.com/forum-garage?filterxt_uid=1507]Visit My Garage[/button]

Visit the Mustang Car Club of New England Facebook Page [button=https://www.facebook.com/MUSTANGCCNE]MCCNE FB Page[/button]

 

Visit the Mustang Car Club of New England Web Page [button=http://www.mccne.com/]MCCNE Web Page[/button]

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I really like this topic. About gear ratios, the main reason for modern overdrive transmissions is to provide better gear ratios for around town driving. The overdrive is to compensate for the higher (numerically) rear end gears. I am averaging about 15.5 MPG mostly highway, my ultimate goal is 25MPG on the highway. I think it'll need to go EFI to get there.

 

One thing to remember is to compensate for oversized tires when figuring fuel economy. I need to multiply fuel economy by 1.1 to be accurate, at 70mph on the speedo my GPS shows 77mph so for every mile on the odometer I've actually travelled 1.1 miles.

 

Theoretically an engine's peak efficiency is at the same RPM level as peak torque.

[align=left]Jeff T.

 

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passengers. [/align]

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