30mpg in the stang, possible?

hllon4whls · Apr 12, 2005

Try running some low rolling resistance tires. That may help get you up closer. Last street 5.0 I have driven was a 93 lx 5sp with 2.73. I dont think that we came close to 30mpg. Stayed around the 24mpg on the hwy. We were never trying to optimize fuel economy.

There is going to be a sweet spot where the engine is not lugging and not spinning too hard to the point to reduce fuel economy. You will have to experiment with different hwy speeds.

Reducing rotating mass in the engine and drivetrain will help. Crankshaft scrapers and windage trays will aid all of this.

Then you have to ask yourself at what point does all of these mods actually pay for the fuel economy gained?

_jb_ · Apr 12, 2005

squeeeg said:
Most t56's do have 2 overdrives. You can always buy them with different ratios.

I must be thinking of a M6 then. My bad.

speed1972 · Apr 12, 2005

Best I've got was 25mpg and that was with 2.73's and AOD. I would imagine that it would have gotten even better with my T5Z. Note: this was my heavy vert with no tune-up, I bought the car a month before and drove to Texas as is.....also very easy on the throttle. I'm sure there is more to be found with a good tune so yes 30mpg is feasible just not practical

cleanLX · Apr 12, 2005

with 3.73's, off road H and bore'd stock MAM being the only mods, and with a cruising speed of 55-60mph, I averaged 29.9 on a ~700 mile road trip.
Car had 30,000 miles on it at the time and ran 13.2's with drag radials out back.
Full synthetics, 36psi in stock sized rubber.
Had myself, my wife(g/f at the time) lacrosse gear and clothing for 2 for a weekend on board.
Had nice weather, and was at sea level or close to it for the entire trip.
Car routinly got slightly better than 26mpg cruising at 70mph, and useing 4th to get by slow traffic on twisty 2 lane segments of the same road.

Snake1 · Apr 12, 2005

I run to a vacuum gauge in my 88 gt with 308's and a 5 speed and have gotten 31.2 miles per gal at 60 to 80 miles per hour over 600 plus miles and very seldom using 5th
5th is to high a gear for the speed,all you do is puke the fuel out the tail pipe.
in fifth you have a hard time bringing the Vacuum off the bottom, revs are to low unless you're up around 100 mph

rd · Apr 12, 2005

30 mpg should be feasible from a 5.0 Mustang. Even Crown Vics can get 25 plus on the highway.

My carbed 79, with a 302, mild Comp cam, Holley 600, a C4 and a slightly loose converter will get 22 mpg on the highway with a 2.73 gear.

This is almost as good as when it was a stock 2 barrel with 2.47 gears!

A well tuned 5 speed with reasonable gears ought to pull 30 with some attention toward mileage.

z9_87 · Apr 12, 2005

vristang said:
HISSIN50 said:

hmm, too bad auto manufacturers did not think of that instead of cruise control. i will stick with CC for best economy.

There was a big push for it at one time, probably the early 80s. The US consumer would never accept such a driving routine! Japan is the only place I have heard of that required it, just not sure of the time frame.

Click to expand...

That's because it's dangerous.

Oh and how is that acetone thing comeing?
To answer someone's question on effects on oil would be about the same as adding any industrial solvent to oil. Also, acetone corrodes plastic and paint very quickly. After all it's fingernail polish remover.

Michael Yount · Apr 12, 2005

" 5th is to high a gear for the speed,all you do is puke the fuel out the tail pipe."

5th is tall to help the car get the better EPA highway mileage rating, not to hurt it. The long 5th gear was picked SOLELY to let the car get a better EPA rating. Same reason the Corvette has a .50 overdrive 6th gear. It reaches it's top speed in 5th -- the long top gears are only there for highway mileage.

If the engine is modded so that torque from 1500-2000 rpm is non-existent, 5th may be a problem. But for stock or mildly modded cars, the long 5th helps gas mileage, it doesn't hurt it.

I've run in both 4th and 5th to check it - both my car, and my wife's Bimmer get better mileage on the highway in 5th than in 4th.

Snake1 · Apr 13, 2005

That may be so in your bimmer or what ever,but in my gt with the 308's in 3rd and 4th running thru the mountains of British Columbia,the tach is running between 28-3200
and the vacuum is between 15-17 inches.
At 50 mph in 5th I'm doing around 1700 on the tach and 5 to 7 inches of vacuum, the minute you touch the throttle, in my humble opinion your engine is not operating efficiently at that low a vacuum.
I do what works for me,and my application,you do what works for yours and we'll all be happy.
PS:
I have a lightly customized 5.0 H O and 44 yrs Commercial driving under my belt

Michael Yount · Apr 13, 2005

Snake - I think the difference in the scenarios is likely the mountains you're running in. We're mostly running on flatlands down here where there is little throttle opening needed (high vacuum) to make enough power to move the car along, even in 5th gear. And the EPA's highway mileage cycle has little in the way of hills in it - that's the target the manufacturers are shooting for.

As for operating efficiency you have a couple of things going on. It takes a fair amount of energy for the engine to work against the throttle - pumping losses it's called. You actually burn fuel creating that vacuum. If all else is equal, you'd like to have the throttle open so the engine doesn't have to work against it - this reduces pumping losses; it's one of the reasons diesels are more efficient than gas engines - no throttle = minimal pumping losses. On the other hand, friction increases with engine speed. All things equal, running the same speed at higher revs will generally reduce efficiency as you have to burn more fuel to overcome the increased friction in the engine.

Generally speaking, if the engine makes enough power/torque to accelerate the car in the rev band you're in - the best fuel mileage is gonna be obtained with a larger throttle opening and lower rpm. That's what the guys were referring to earlier.

On the flatland cruises however, almost all these V8's make enough torque to lumber along at low rpm - and that's why the manufacturers equipped all of them with really long top gears - to enhance fuel mileage at cruise.

Lastly, if you read the previous post more closely, I stated that my 5.0L also gets notably better mileage in 5th than 4th at cruise. Running 60-65 mph in 4th the car gets about 20-21 mpg; in 5th it's 24-27. Sorry - no BC mountains to experiment with down here.

Snake1 · Apr 13, 2005

Michael Yount said:
Snake - I think the difference in the scenarios is likely the mountains you're running in. We're mostly running on flatlands down here where there is little throttle opening needed (high vacuum) to make enough power to move the car along, even in 5th gear. And the EPA's highway mileage cycle has little in the way of hills in it Sorry - no BC mountains to experiment with down here.

Too bad,you're missing some great scenery and some Great driving
I guess I must be doing something right with 31-32 mpg highway and 19-22 in city stop and go
Don't forget I"ve still got the speed density in the 88
Ever get up this way I'll take you for a ride in the Mts.

I Live on the ouskirts of Sechelt BC here's a pic

HISSIN50 · Apr 13, 2005

Snake, i think he chooses to use the bike for the twisties - i know i do.

94GT40 · Apr 13, 2005

mr.b said:
what would it take to get as close to 30mpg (on the highway) as possible with the stang. My thoughts are, 5 speed, 2.73 gear, all synthetics throughout the drivetrain, lean fuel mixture (with egr functioning good), drop some weight, pump up the tires, what else? This is just something i have been thinking about with the costs of gas rising.

This is something I'm actually working on right now. I have 3.08 gears. I have tried to make my shift points at about 2000 rpm and cruise mostly between 1500 and 2000 rpm. I do a lot of 2 lane highway driving averaging about 100 miles each day. My best milage so far is 24.7.

I'm hoping it will improve in a few weeks when I install my GT-40p heads, headers and Cobra intake. I will be shooting for the 30 mpg number.

I'm also gonna try the acetone thing.

vristang · Apr 13, 2005

I don't know if using acetone will improve fuel economy, or completely destroy the motor. I have yet to do any research on the topic, so... I will let someone else try it on their motor first. Good Luck!
Another consideration that has yet to be mentioned is cost per mile. I don't know what it will cost to treat a tank of fuel with acetone, but if its too expensive then the increase in fuel economy will be offset by the cost of the acetone. Fuel economy is a standard that the manufacturers use to compare their vehicles without mention of price changes in fuel. What the consumer should be concerned with is $/mi.

Mark89coupe · Apr 13, 2005

jackchan said:
3) 195degree thermostat..........I hear people running 170 and below suffer from low horsepower and flooding i.e. the computer is actually thrown into a choke loop and therefore uses more fuel and runs actually worse.
Jack

I have a jet performance chip in my car and a 180 degree thermostat. I thought this was perfect for the 5.0. How can I tell if its in choke mode?

vristang · Apr 13, 2005

Consensus seems to be that a T-stat under 180 will cause these problems. With cold coolant flowing the computer assumes the engine just started. Most people will use the cooler stat to band-aid a cooling system problem. I tried it once. Lost power and fuel economy, and still had cooling issues.
The downside is that the engine never gets up to a good running temp. In other words you have to use some of the fuel in the combustion chamber to re-heat the cylinder walls on each cycle. The result is less power and fuel economy. Emissions will be affected too (HC worse, NOx better). Obviously there is a trade-off between getting colder/denser air into the chamber and keeping heat in the cylinder (thermal efficiency).

You should be fine with a 180. A stock stat would probably provide better economy though. ?

88GT_TTOPS · Apr 13, 2005

my stang is an 88 GT T-tops, with a 100k miles at the time

MODS at the time of max MPG
AOD (not a mod an AOD is a de-mod )
1.7 RR
ported upper and lower stock intake
65mm t-body
mac shorties
h-pipe no cats
flowmaster 2 chamber w/ dumps
at the time it had 2.73 gears
K&N
19 degree timing
normal size tire and inflation
all smog crap removed and plugged
accel coil, dist. cap, wires

a buddy and I with a small but heavy tool box and luggage went the 350 mile trip from Dayton OH to Gatlinburg TN getting 31 mpg on the way there and 33 on the way back with the CC on at 70-75 mph
did the same trip later, with 3.73's and still got upper 20's

Mark89coupe · Apr 13, 2005

Why do chip company's recommend a 180 degree stat? Would it hurt if I went a little higher? Im doing an engine swap in a few weeks.

HISSIN50 · Apr 13, 2005

people who datalog can see when the puter enters full closed loop (the car hits closed loop within a couple mins or less, but with tables for enrichment till it reaches warm strategy). seems to me there is a magic full warm strategy threshold at 178*F.

mr.b · Apr 13, 2005

i am glad to see all the responses to this thread. It seems that 30mpg can be possible. Not that the stang was designed for mpgs, but when gas is 2 dollars plus anybody starts to take notice of their gas mileage and any savings possible.

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