32 mpg?

[Sixty_Six_Stang]

So today before work I topped off my gas tank for my 66 mustang and recorded the miles on my car. After driving all day with about 90% being on the highway I topped off my tank again and recorded the miles on my car. Then I thought it would be fun to see what sort of milage I was getting and after I crunched the numbers it came out to about 32 mpg and I was shocked. I've got a freshly rebuilt 200ci with the only upgrade being an electronic ignition but even then I was only expecting maybe 24-26 mpg. Is anyone else's car getting over 30 mpg? Or is my mile counter thing just off?

91931-91807=124 miles then divided by 3.8 gallons = 32.6

 

[Asa]

Rickwrench was hitting 35 or so MPG with his falcon, he had a T5 conversion and kept it at 65 MPH though

it's possible, but in a stocker? ehhh.....

 

[shmoozo]

Run a few full tanks through the car while keeping a running count of how many gallons you use and how many miles you drive. You'll get a more accurate number that way than you will with just one partial tank. Keep in mind that it may be that the tank wasn't topped off as much when you filled it the second time ... or something.

If you can do the numbers after about 1000 miles or so and still get the same result, then you've got something.

 

[Ronbo]

3.20 gears in a 2.80 car? Show more than actual miles on the odometer. Check the tag on your axle against the build code.

Ron

 

[CobraSix]

Those seem really high. I've hit 30MPG with some light modifications and a T5 way back when. Stock however, only managed 26MPG max.

I would check your odometer against the mile tickers.

 

[Harte3]

Yup, odometer check is in order.

 

[buzzA4]

Must have been down hill with a tailwind, both directions?

Try going for a month, recording all the gas you put in and mileage.

Do you have stock tire size or a lower profile tire?

If I am not mistaken, low profile tire have a smaller circumference and travel less distance per rotation. This would give you a higher than actual odometer reading and higher than actual speed indication.

However, I think that will only account for 5-10% at the most.

 

[MPGmustang]

wow, 16 x 32.6 = 521 miles per tank, that's past my goal

You have c4 I presume? or manual?

dito on try doing it for longer trips and multiple tanks of gas.
for the speed find one of those "your speed sign" and test it @ 30mph ish to your spedometer

cool keep it up,
Richard

 

[early ford fan]

mpg?i see you have the vaporizer and only get 21 mpg.i was hoping thse were better for more mpgs.any thoughts?have you tryed the holley weber?

 

[yodabiri]

I dont want to steal the thread, but I have a question of my own regarding rediculously low gas mileage. I swapped a 250 and t5 in my 65 mustang this past summer. I was getting 21 mpg in the city before the swap with a 200, 3spd, an autolite 1100, and DUI. Now I can barely get 14mpg in town with my 250, t-5, DUI, and autolite 1100 (I am waiting for some headwork to get done on my spare head so that I can put a bigger holley carb on it, plus for some reason carter yf carbs refuse to work for me and the autolite makes the car purr very smoothly and has good low end torque). Does anybody have any ideas why this drop in mpg could have happened? Everything is essentially the same except the motor and trans, and I was expecting a small drop in gas mileage with more cubic inches, but a 33% drop is rediculous! Its like driving a v8 now, but without the horsepower.

Any input is welcome

 

[Ronbo]

Did you change the speedo gear in the tranny when you did the swap? Hows it run with the 3.20 gear set (I'm assuming thats what you have)? I'm pretty sure folks with that same set up hit 20 mpg and higher. Again, speedometer error can throw ya big time on figuring yer fuel consumption.


Ron

 

[yodabiri]

I didnt change the speedometer gear, but I drove the car past a speed detector sign (a couple of times just to be sure) and it showed essentially the same speed that my speedometer showed, so I dont think it is very off on that. One thing I have noticed and forgot to mention is that the carb does sound weird when the accelerator is pressed slightly. It sounds like its spitting fuel in, but when the throttle is opened wider, the sound is not noticeable. I have checked and cleaned it and it still does that. Maybe the fuel pump is producing too much flow and thus there is an incorrect pressure at the carb? Or maybe my accelerator pump is not working properly. (I rebuilt the carb a couple of years ago and replaced the diaphragm)

Thanks for the input!

 

[rommaster2]

Its like driving a v8 now, but without the horsepower.

Ha my sisters warmed up 289 gets about 20mpg

Sounds usually won't tell you much, how does the car run, have you pulled the plugs to read them and see if your running really rich? If anything the 1100 should barely get that thing up past 3 grand rpms.

 

[MPGmustang]

mpg?i see you have the vaporizer and only get 21 mpg.i was hoping thse were better for more mpgs.any thoughts?have you tryed the holley weber?

actually 21.3mpg has been my best mileage ever, I was getting 13-14mpg and didn't like it so i bought the 1100v and wow bolt on gas saver!!! 33% increase was nice... thinking about that i think i could've stolen your mileage ... i don't have a DUI (yet) and my distributor is from 65 (little weak) when my 200 is from 68 (they have a stronger spring in the vacum advance modual, so right now i get a hell alot of tick if i punch it) and i'm working on the t5 installation so i hope to raise that more

Richard

 

[yodabiri]

Actually it manages to run it up to 5000 rpm surprisingly. The car runs smooth (way smoother than with either of the two yf's that I have tried). Also it has awesome torque in the low range which is difficult to keep under control on corners or in the rain (I actually spun out a couple of weeks ago on a long sweeping turn after a hard rain and a little too much gas and too much oversteer). But anyways when I tried the carter carbs, I got about the same amount of mpg (14 or so). I will try and read the plugs tomorrow to see what color they are. I did that a while ago (right after the swap) and they were a dark brown color, but not black of sooty.


Thanks for the responses!

 

[fphillips]

Actually it manages to run it up to 5000 rpm surprisingly. The car runs smooth (way smoother than with either of the two yf's that I have tried). Also it has awesome torque in the low range which is difficult to keep under control on corners or in the rain (I actually spun out a couple of weeks ago on a long sweeping turn after a hard rain and a little too much gas and too much oversteer)...

Well, there's your problem - you drive like a maniac!

 

[yodabiri]

Well, there's your problem - you drive like a maniac!

I have been very conservative with the throttle since the swap to try and get a decent mpg reading. I spun out because I very slightly tapped the throttle and there were white painted lines on the road (which was wet from the rain), which caused the wheels to lose traction. I am actually a very safe driver most of the time, plus I drive exactly the same as I did before the swap, maybe even more carefully, and my mileage has gone way way down. So maniacal driving is not the issue.

 

[MPGmustang]

i tried this too, with my older carb (holley 1940) i got better gas mileage when i drove normally, aka recklessly, i got 14-15mpg, but when i went with traffic i got 13-14mpg, it was only 1mpg more but hey "i was saving gas officer"

now that i have the 1100v i'm seeing the same pattern, 17 with traffic, 19 ahead of traffic

try it, i did and for some reason it likes to go faster... don't know why but i don't care, hell i'm saving money

Richard

 

[CoupeBoy]

my sisters warmed up 289 gets about 20mpg

I'd like to know how that happens... My '68 Mustang has a 289/C4/3:00 rear. Engine has Edelbrock 600 K&N 14" open element, performer intake, and matching edelbrock cam/lifters, DurasparkII dist, GM ingition module, generic 12v coil, plugs are a nice light mocha color, I've rejetted/changed metering rods, and adjusted the accellerator cam so there is almost no bog during transition when opening the 4bbl, it gets 16mpg on a good day (when I keep it below 75) and 14mpg on any tank that sees highway miles. On most days I do drive it like I stole it but I have *rarely* drove a whole tank out at 'rational' speeds with no appreciable difference in MPG. It's OK to tell me what I'm doing wrong.. Dad does all the time

My only real hope is to put in an overdrive transmission and start driving like I've got all day to get there..

Here's another story of weird gas mileage.. Last Spring we went to Jackson Wyo for my sister-in-law's wedding and the Antler Fest (yes, I R a redneck) we drove out '06 equinox, which consistently gets 19mpg winter and anywhere from 21.5-23mpg in the summer up and down the ND higways. Anywho we filled up the tank in Jackson Wyo and drove to Idaho Falls, ID and filled up again there. That tank averaged 35.6mpg, which is still a mystery to me, I know it was a slower road, but there's no way it was downhill the whole distance. Next tank it was back to 'normal' ~22mpg.

-ron

 

[early ford fan]

i brlieve the cam in the 250 was retarded for emissions.maybe a 1969 timing chain and gears would help.