Drving faster, in my experience does not make a significant change in mileage...

Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take that
you speed kills freaks and tree huggers. Anyhow...

This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears. The reason
I believe it made no significant difference is because my engine has a lower
BSFC at 3000 RPM (85 MPH) than at 2400 RPM (70 MPH), so the increased drag
from the air is compensated for by greater fuel efficiency at that RPM. My
engine should have the least BSFC in the 3000-3500 RPM range. Get out of
that range, up or down and efficiency decreases.

It it's of any interest the mileage was 14.5 at 70 MPH and 14.2 at 85 MPH. I
expect to gain another MPG or two when I get my timing dialed in just where
the engine wants it. Right now I've only got 30* total mechanical in by 3500
RPM or so plus whatever vacuum it takes while cruising. I'm gonna give it a
few more degrees machanical and hae it come in by 2500-3000. Trick is to get
the curve just right so it doesn't ping on 93 octane and I can still have a
dencet amount of initial advance (10* now). Come spring I'll have new heads
though and I'll be able to run on 87 or 89 with as much timing as the engine
wants. No more of this 11:1 crap. That and an electric fan which should get
me another MPG or two on top of wahtever I get from getting my timing
straightened out.

Anyhow, if anyone else has calculated their mileage at different speeds I'd
be interested to know what it is at the different speeds and what type of
car it is.

Cory

Interesting Cory. Each vehicle seems to respond differently in this regard.
For example:

We have a 1997 Grand Caravan (3.3 Pushrod V6) and we get the best highway
mileage at around 70-75MPH (about 27-28MPG). Drive it at 60MPH and the
mileage drops to around 26-27MPG (although last trip at mostly
non-interstates at 50-60, with some below 50 got 29MPG, now that I just
checked....hmmm...). Mileage seems to start going back up again below
50MPH...but that is just a "feeling". It would be interesting to graph
this. But generally this vehicle does better with gas mileage at 70ish
compared to 60ish by about 1-2MPG. We have 7+ years of records and it's
been consistent the whole time...except this last trip is a strange anomoly.
Either I had a lot more 40-50 MPH driving in there than I thought OR I must
not have done a comparable fillup after the trip that time!

Now, on the other hand, the Wife's 2003 Stratus (2.7 DOHC V6 Duel Fuel E-85
Engine) does NOT seem to do better at 70+. She just took a 2400 mile round
trip averaging 68.8MPH (including the 10-15 minute rest stops every 2 hours)
Since she drove the 1200 miles straight through each way (I think she's
crazy!), she was religious with keeping the rest stop schedule. So, remove
the time for the stops and she probably really averaged 75MPH+ when actually
on the road. She tells me she kept it at 80+ most of the way, but that
would be difficult, I would think. Anyway, her round trip mileage was
27.3MPG. When I drive her car on road trips at around 60ish (I drive slower
than she does!), I usually get 30-32MPG. We've never had it below 60 for a
long enough drive to see if it does better or worse there...just don't know.
So her car does better with gas mileage at 60ish compared to 75ish by about
4-5MPG. Now one dynamic...she had it loaded fairly heavy for her trip...but
since there was no other passenger with her, probably compensates for when
I've driven with a passenger. Interestingly, her going mileage was about
1MPG lower than her return mileage. She did the trip out 1 hour quicker
than the return trip...but the weather was about 20 degrees warmer on the
return trip (less dense). So that *may* reinforce the theory that, with her
car at least, the better mileage is acheieved at the slower speed.

Both vehicles run about 2200RPM at 70MPH...so the gearing is near identical.

By the way...My 1967 GTO was happy to get 7-8 MPG city OR highway (made no
difference). That 411 rear-end would turn 3100RPM at 60MPH. You're doing
good at 14+MPG in that vintage car, I would think!

In article >, Cory Dunkle wrote:
> Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take that
> you speed kills freaks and tree huggers. Anyhow...
>
> This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.

2.80 is good milage axle. Anyways.... if you're going to be going over 70
regularly and it's not on an empty interstate I suggest you upgrade the
braking system on that car.

On Wed, 19 Jan 2005 23:06:54 -0600,
(Brent P) wrote:

>In article >, Cory Dunkle wrote:
>> Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take that
>> you speed kills freaks and tree huggers. Anyhow...
>>
>> This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.
>
>2.80 is good milage axle. Anyways.... if you're going to be going over 70
>regularly and it's not on an empty interstate I suggest you upgrade the
>braking system on that car.
>

He should upgrade the whole ****ing car. **** like 35 year old Fords
belong in museums

In article >, Olaf Gustafson wrote:
> On Wed, 19 Jan 2005 23:06:54 -0600,
> (Brent P) wrote:
>
>>In article >, Cory Dunkle wrote:
>>> Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take that
>>> you speed kills freaks and tree huggers. Anyhow...
>>>
>>> This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.
>>
>>2.80 is good milage axle. Anyways.... if you're going to be going over 70
>>regularly and it's not on an empty interstate I suggest you upgrade the
>>braking system on that car.
>>
>
> He should upgrade the whole ****ing car. **** like 35 year old Fords
> belong in museums

Just trying to troll? I suggest you work on getting SUVs off the road if
you're going to worry about '68 galaxies on the road. The former is a
much larger problem wrt behind-the-times handling for passenger vehicles
etc.

On Thu, 20 Jan 2005 10:52:35 -0600,
(Brent P) wrote:

>In article >, Olaf Gustafson wrote:
>> On Wed, 19 Jan 2005 23:06:54 -0600,
>> (Brent P) wrote:
>>
>>>In article >, Cory Dunkle wrote:
>>>> Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take that
>>>> you speed kills freaks and tree huggers. Anyhow...
>>>>
>>>> This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.
>>>
>>>2.80 is good milage axle. Anyways.... if you're going to be going over 70
>>>regularly and it's not on an empty interstate I suggest you upgrade the
>>>braking system on that car.
>>>
>>
>> He should upgrade the whole ****ing car. **** like 35 year old Fords
>> belong in museums
>
>Just trying to troll? I suggest you work on getting SUVs off the road if
>you're going to worry about '68 galaxies on the road. The former is a
>much larger problem wrt behind-the-times handling for passenger vehicles
>etc.
>
>


That doesn't change the fact that he should get a better car.

Olaf Gustafson wrote:
> On Thu, 20 Jan 2005 10:52:35 -0600,

> (Brent P) wrote:
>
> >In article >, Olaf
Gustafson wrote:
> >> On Wed, 19 Jan 2005 23:06:54 -0600,

> >> (Brent P) wrote:
> >>
> >>>In article >, Cory Dunkle
wrote:
> >>>> Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG.
So take that
> >>>> you speed kills freaks and tree huggers. Anyhow...
> >>>>
> >>>> This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.

> >>>
> >>>2.80 is good milage axle. Anyways.... if you're going to be going
over 70
> >>>regularly and it's not on an empty interstate I suggest you
upgrade the
> >>>braking system on that car.
> >>>
> >>
> >> He should upgrade the whole ****ing car. **** like 35 year old
Fords
> >> belong in museums
> >
> >Just trying to troll? I suggest you work on getting SUVs off the
road if
> >you're going to worry about '68 galaxies on the road. The former is
a
> >much larger problem wrt behind-the-times handling for passenger
vehicles
> >etc.
> >
> >
>
>
> That doesn't change the fact that he should get a better car.


Why? It'll probably last longer than any new car.
I think you need to get a better attitude.

nate

"Brent P" > wrote in message
...
> In article >, Cory Dunkle wrote:
> > Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take
that
> > you speed kills freaks and tree huggers. Anyhow...
> >
> > This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.
>
> 2.80 is good milage axle. Anyways.... if you're going to be going over 70
> regularly and it's not on an empty interstate I suggest you upgrade the
> braking system on that car.

I'm thinking I may do just as well with a 3.25 or 3.50 as it would get my
RPM where the motor is more efficient but at a lower speed that I normally
travel on local trips. Anyhow, the transmission slips on the 2-3 shift until
warmed up when the weather is below freezing. So when it goes I'm gonna
upgrade to an AOD for mileage and put something in the neighborhood of
3.50:1 - 4.11:1 gears out back. Should give me a slightly better final drive
for lower RPM and give much better acceleration with that little 302. I may
even see an increase in around town mileage. Anyhow, for the time being I
just shift manually for the first 2-3 minutes and when I go to 3rd I let go
of the gas while it shifts so it doesn't slip. Seems to be a problem FMX
transmission gets after a while. My '67 had the same problem though it
developed it around 200,000 miles, the '68 has about 113,000 miles, but then
again when my uncle drove it he never put fluids in it or anything.

As for the brakes, I generally don't drive faster than 80-85 as that's about
the upper limit of what my car can do in a full-out emergency stop and not
have the brakes overheat as I approach a stop. These old Gals have big
2.5"x11" drums all around which stop pretty well compared to other drum
brake cars, like Mustangs which have tiny drums. I'm keeping my eyes open
for a good disc brake donor though. It's not on the top of my list of things
to do but should I come across the parts I'll probably snag them when I have
the chance. Would be a nice thing to have since I do a fairly large amount
of highway miles and most of the econo-boxes on the roads can stop pretty
darned quickly.

Cory

Cory Dunkle wrote:

> "Brent P" > wrote in message
> ...
>
>>In article >, Cory Dunkle wrote:
>>
>>>Driving at 85 MPH vs 70 MPH only reduced my mileage by .3 MPG. So take
>
> that
>
>>>you speed kills freaks and tree huggers. Anyhow...
>>>
>>>This is in my '68 Galaxie 500 with a 302, FMX, and 2.80:1 gears.
>>
>>2.80 is good milage axle. Anyways.... if you're going to be going over 70
>>regularly and it's not on an empty interstate I suggest you upgrade the
>>braking system on that car.
>
>
> I'm thinking I may do just as well with a 3.25 or 3.50 as it would get my
> RPM where the motor is more efficient but at a lower speed that I normally
> travel on local trips. Anyhow, the transmission slips on the 2-3 shift until
> warmed up when the weather is below freezing. So when it goes I'm gonna
> upgrade to an AOD for mileage and put something in the neighborhood of
> 3.50:1 - 4.11:1 gears out back. Should give me a slightly better final drive
> for lower RPM and give much better acceleration with that little 302. I may
> even see an increase in around town mileage. Anyhow, for the time being I
> just shift manually for the first 2-3 minutes and when I go to 3rd I let go
> of the gas while it shifts so it doesn't slip. Seems to be a problem FMX
> transmission gets after a while. My '67 had the same problem though it
> developed it around 200,000 miles, the '68 has about 113,000 miles, but then
> again when my uncle drove it he never put fluids in it or anything.

Unless you really feel the need for the OD, I'd keep the FMX. AFAIK
it's closely related to the old Ford-O-Matic and therefore the
Borg-Warner automatic that Studebaker used from 56-64, and that tranny
is one of the most underrated units out there - very durable, reliable,
and basically abusable. I know a guy that was pumping over 600 RWHP
through a Powershift (basically a fancied up HD Flightomatic) and
ditched it for a THM400 because everyone told him it would be
stronger... and promptly blew the THM400... I'm really not sure what
the reliability of a good AOD is, but I seriously doubt it's as
cast-iron, dead-nuts reliable as the FMX/Ford-O-Matic/Flightomatic.

Of course, if you have a 9" rear, it's trivially easy to play with the
rear gear ratio, and I can see the appeal of having a tranny with a
wider gear spread. So if that's what you really want, and this car you
think is a keeper, by all means go for it. I guess I just felt
compelled to stand up and defend the honor of the FMX there for a second

>
> As for the brakes, I generally don't drive faster than 80-85 as that's about
> the upper limit of what my car can do in a full-out emergency stop and not
> have the brakes overheat as I approach a stop. These old Gals have big
> 2.5"x11" drums all around which stop pretty well compared to other drum
> brake cars, like Mustangs which have tiny drums. I'm keeping my eyes open
> for a good disc brake donor though. It's not on the top of my list of things
> to do but should I come across the parts I'll probably snag them when I have
> the chance. Would be a nice thing to have since I do a fairly large amount
> of highway miles and most of the econo-boxes on the roads can stop pretty
> darned quickly.
>
> Cory
>

You may want to consider an aftermarket disc brake conversion; a lot of
late '60s cars used 4-pot fixed calipers which work, but are expensive,
finicky, and don't really work any *better* than a cheaper, simpler
single or dual piston caliper (which is usually what the aftermarket
kits have)

nate


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