Gas mileage

Asked by Feb 17, 2013 at 10:31 PM about the 1984 Ford Mustang LX

Question type: General

I have a 1984 mustang lx convertible and I'm getting about 80-90 miles on a 14 gallon tank. Now that's shitty. It is a
3.8 v6 automatic. I really REALLY want to get rid of the car because of it. When I fill it up, the needle goes a little
over the "F" and it takes about 25-35 miles till the needle gets JUST past the "F". After that, it just goes straight to
hell. Pleas help.
(That's my mom in the photo.)

11 Answers

sakes, how many miles are on this buggy. You're lucky this one still runs. if you were serious about solving this gasguage problem would take accessing the inside of the gas tank- My advise, depending on the mileage and interior condition and the smell of the exhaust, if it's runnin that terrible exhaust is going to be stinky. Sell it off, and buy something safe. This buggy don't have no airbags.

It's got 60,700 on it. The exhaust does smell a little. It's just such a pain in the ass to try to pay for gas and save up. I'm putting in like 50-60 dollars every two weeks and its damn near impossible to save.


That's 6.4 MPG. Back in the '80s that's what my '66 Cadillac got around town in the winter. That car had the V8 429 &weighed two tons! If you're driving it like a race car there's the problem. Jackrabbit starts &cruising at high speeds will kill your gas mileage. Is the car running normally otherwise? Any black smoke from the tailpipe? Any chugging or stalling? Check the fuel system for leaks. If it has a carburetor check that the choke isn't stuck partly closed. Is the transmission shifting properly if it's an automatic? A malfunctioning transmission will kill gas mileage too. Also, invest in a locking gas cap. With todays high gas prices it's not inconceivable that your the victim of someone siphoning gas from your tank. HTH. -Jim


gotta b runin rich like 7 mile a gallon gotta b kicking black carbon out the tail, needs some tuneup thats all, if you can get out of smog tests' gut the good tuneup thru intake blow clean exaust,adv. timing a tweek,dis egr.vac. and go to the races thats a nice old car ,ask mom!


For gas mileage to be that poor, the car would be running so badly you would hate to drive it! How much gas are you putting in when you fill it? How many gallons, I mean. When last was the oil changed? When was the last tune up? Is the timing set correctly? Go through all the basics, and concentrate of things like spark plug gap, timing, carb settings. You NEED to fix this soon, or your catalytic converters are going to be plugged. It is possible that is the problem now, especially if the car is sluggish. There are many things, and a LOT of them are simple basic maintenance.


Like Michael said - fresh plugs and air filter. Check the tire pressures. Learn to compute in miles per gallon instead of miles per tank to see if it improves.

No black smoke or anything. Had an oil change about a month ago. I always fill it up completely. I feel like I have to drive like a damn grandmother in that car so ther is absolutely NO jackrabbit-ing. It does stall when I "turn key and go". Like I have to wait for like 5 minutes before I can start to drive or else it will stall. Also, my gas tank is sort of leaning to one end? When you're looking at the back of the car, you can see the whole bottom half of the tank and the left side is hanging further than the right (which is where the gas cap/where I put in gas) also, the whole car is only being moved by the passenger rear wheel. I don't know if that's how that's supposed to be or not, but that's how it is. Ever since I got it (about late June) never has it had a tune up. It is an automatic, shifts smoothly. Other than that, it runs rather well. Lastly, the air filter which is on the top of the engine, there should be like a tube that runs off of that and down the side of the engine and out if the car. Yeah, I don't have that... (NOT my actual engine, but the thing coming out of the left of the golden circle piece. That's what I don't have.)

by filling it up completely, you're drowning the charcoal canister. Your evaporative system is malfunctioning, causing the bad mileage.


Sounds like a carbuerator problem. There should also be a pre-heater hose going from the air cleaner snorkel to a heat stove on the exhaust manifold. This pre-heats the air so the choke doesn't have to stay on as long. What's the idle speed set at? In drive and fully warmed up it should idle at about 650 RPM. Sounds like you're also missing a strap for the gas tank. I'd get that fixed asap. Don't want your gas tank falling out!! That would obviously NOT be good!! HTH. -Jim


Well maybe you good people could read my question on the ford see what u think having similar problems. Just filled up went one hundred miles used half a tank but is running fine with a vacuumed leak


I'm wondering if you have a leak in the tank, too. Those straps normally last a very long time, but you have one either broken or missing. If it broke, you could very well have a leak in the tank, since that normally rusts out before the strap. You likely only have ONE of the snorkels on the air cleaner. The 2 snorkel job is very rare. It sounds to me as though there are a bunch of little issues adding up to a major problem with the car. The first step is a good, very thorough, major tune up and service. When was the coolant last changed? When was the thermostat done? I would do those as a pat of the servicing. A stuck thermostat will cause you to warm slowly, and cause considerable case consumption. With the 6, you should be doing about 300 miles on the highway, or about 200 in the city. As you can see, you are a LONG way off that. I would hazard a guess and say that if you spent about $200 on the car, doing the work yourself, you could make a massive difference to the consumption. You can also do it in stages, too. Start with new plugs and wires for about $60. Then do the rotor and cap, about $10. Do the fuel filter ($5), set the timing (free), set the carburetor (free). First thing, though, is that gas tank. The straps will cost about $40 for the pair, and if your tank is leaking, you will need to spend about $150 for a brand new one. Thing is, if you do all of this and get the gas mileage back close to where it belongs, your payback for the investment will be about a month. Everything you save after that is gravy, and that is an awful lot of gravy waiting for you!

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