Worst gas mileage possible with a stock motor

87MustangGT5.0 · Mar 23, 2009

I have a 92 mustang 5 speed with moroso intake, march pullies, bbk headers, bbk o/r H, and mac catback.

I am getting about 180miles to a tank of gas shifting every time below 2500rpm.

I have changed everything on this car including
-plugs
-wires
-cap and rotor
-fuel filter
-pcv valve
-both o2 sensors
-set timing at 14
-seafoam

I just dont get this, it went from about 240 to a tank to 180 suddenly. The car seems to have lost some low end response but is strong on full throttle. Where should I go with this, maybe to the fuel pressure? There is no black smoke. Thanks

Darkwriter77 · Mar 23, 2009

1. Pull trouble codes;
2. Pull/check/clean the EGR valve;
3. Check all vacuum lines for any broken, disconnected, or leaking lines;
4. Pull and check IAC sensor (sometimes they get gummed up with gunk);
5. Check/clean all ground cable contact points;
6. Perform weight reduction modification upon accelerator pedal by deleting lead foot.

87MustangGT5.0 · Mar 23, 2009

there are no trouble codes, vacuum lines all check good, and my foot is so light that I get made fun of.

mavmavv · Mar 23, 2009

Ive never gotten above 180 for a tank ever. Consider yourself lucky to be getting that.

tim281 · Mar 23, 2009

Could be the gas station....Maybe they switch fuel sources and are using the 10% ethonal stuff.
Did you get new tires with high rolling resitance?

dgollem · Mar 23, 2009

What's the Miles per Gallon?? Miles per tank can vary because of the gas guage. Fill the tank all the way up drive some miles maybe even 180, refill the tank. Divide the miles driven by the gallons required to refill the tank and you will have a pretty good measure of your MPG. For example you fill the tank drive 180 miles refill the tank it takes ten gallons 180 divided by 10 = 18 miles per gallon, which would not be to bad for a 5.0 and city driving

ID89GT · Mar 24, 2009

Ha I barely got 145 on my last tank, but I was having lots of fun with it with the snow being gone

93 LX · Mar 24, 2009

In my case one of my cats flipped and caused a blockage in one of the banks. I had it fixed, replaced my O2s and am now getting 260 to 280 per tank full. Thats 13 gallons per fill up.

jrichker · Mar 24, 2009

Did you dump the Key On Engine Running codes?

87MustangGT5.0 · Mar 24, 2009

I always use premium shell gas and its always 25 bucks to fill up so like 12 gallons each time

dcurtis · Mar 24, 2009

My car currently only has headers, offroad h-pipe, flows dumped and a set of 3.73 gears and I am currently at 220 miles since I filled up last month, I am going to run it till it dies to find out how far it will go as of right now Im at about 15 miles per gallon, but I'm still going so I will be sure next week when it runs dry.

Darkwriter77 · Mar 24, 2009

dcurtis said:
My car currently only has headers, offroad h-pipe, flows dumped and a set of 3.73 gears and I am currently at 220 miles since I filled up last month, I am going to run it till it dies to find out how far it will go as of right now Im at about 15 miles per gallon, but I'm still going so I will be sure next week when it runs dry.

Running your tank dry is a good way to kill your fuel pump in short order.

BLOWN347STROKER · Mar 24, 2009

You should feel real lucky getting that. I only get about 100 miles per tank of gas which is somewhere around 10 miles to the gallon. My car is by no means stock but that still is real bad.

RAYMOND259 · Mar 24, 2009

I only get 11 miles per gallon in the city,with trick flow kit with Aod tranny

Modular2v · Mar 24, 2009

wow! Wonder why my gas mileage is so much better? With my mods in my sig im getting 18mpg.

Duncan McDougal · Mar 24, 2009

87MustangGT5.0 said:
I have a 92 mustang 5 speed with moroso intake, march pullies, bbk headers, bbk o/r H, and mac catback.

I am getting about 180miles to a tank of gas shifting every time below 2500rpm.

I have changed everything on this car including
-plugs
-wires
-cap and rotor
-fuel filter
-pcv valve
-both o2 sensors
-set timing at 14
-seafoam

I just dont get this, it went from about 240 to a tank to 180 suddenly. The car seems to have lost some low end response but is strong on full throttle. Where should I go with this, maybe to the fuel pressure? There is no black smoke. Thanks

You try sensors yet? When my temp gauge didn't work I replaced my temp switch and temp sending unit. When I replaced the latter my gas mileage went from 8 mpg to 15 mpg. When you have a bad temp sending unit your car will run open cycle (start up mode) all the time, so it will run pig rich.

pudman · Mar 24, 2009

guess I'll chime in. i get 230-250 per tank. highway city combo. 250-280 on a good road trip. My engine is totally stock except for an MSD box. I run 87 grade gas. Anything but Shell or Arco. My car runs like poop on those two. Between being a vert, 6pt roll bar and all the other weight adding goodies I have including my 200lb fatness..I don't know. Maybe it's me. I must be doing something wrong especially living in So. Cal. I don't get to go to fast very often

C&SMustang · Mar 24, 2009

Modular2v said:
wow! Wonder why my gas mileage is so much better? With my mods in my sig im getting 18mpg.

5 speed? That would explain the good gas mileage.

dcurtis · Mar 25, 2009

Darkwriter77 said:
Running your tank dry is a good way to kill your fuel pump in short order.

That pump will be pulled out next week anyways, I have a holley 190lph pump and a new sending unit to install (FINALLY)

87MustangGT5.0 · Mar 25, 2009

Duncan McDougal said:
You try sensors yet? When my temp gauge didn't work I replaced my temp switch and temp sending unit. When I replaced the latter my gas mileage went from 8 mpg to 15 mpg. When you have a bad temp sending unit your car will run open cycle (start up mode) all the time, so it will run pig rich.

Thinking of that, my temp guage never goes up above the second line from the bottom at most?

Worst gas mileage possible with a stock motor

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