The least fuel-efficient car EVER posted here...
 

Hello,
I'm going to start this with my dilemma. I'm driving a 1991 Mercury Grand Marquis with a 5.0L V8, 150hp. It's got about 125,000 miles. Now, it'll get 26-27mpg on the highway. Not bad! HOWEVER....around town, where I mostly drive it, I have some major problems. 17mpg is normal, and 15 is definitely not unheard of.

I've read that on some cars, the intake is so restrictive that the car burns more fuel than is necessary. I have also read about Mustangs with the same basic engine components but upgraded to 250 or so horsepower getting 30mpg. Would a less restrictive intake do anything for me? Or should I just try it and see?

I'd get a more fuel-efficient car, but I'm 17 and can't afford one at the moment...and besides, I like the Merc and it's in great condition. I'm including a few pictures of it.

http://i48.photobucket.com/albums/f2...world/car3.jpg
http://i48.photobucket.com/albums/f2...world/car1.jpg
http://i48.photobucket.com/albums/f2...world/car5.jpg
http://i48.photobucket.com/albums/f2...world/car4.jpg

Now, being that I drive 15 miles each way to work via a construction zone, dumping the spare tire is probably out of the question, even in search of mileage. Any ideas (non-body-related...aero is not much of a problem, at least less than you may think) will be welcomed with open arms!

I'm no automotive engineer but I can't see how opening up the intake passages would help. You want to be operating it with the intake flow kept minimal. I'd stick to basics. Pump up the tires. Learn to coast. Accelerate moderately in lower gears and learn when to lift-off to get into the next gear sooner. Try and keep it in top gear and once in top gear, accelerate slowly or read the road and use downhills for that. Go over hills like you're rising a bicycle - that is let the speed bleed like you only have a lawnmower engine and then recoup it on the other side.

get a vacuum gauge, that will help you see how much fuel you're using.

I totally understand the dillema. I'd get a glass jar and put a quarter in it everytime you have to drive the PIG. When you get $1000, go buy a used Honda Civic, stick, plain jane. Install a new timing belt and water pump and start saving some money.


The problem is that somehow FORD figured out a way to make an engine, drive train that gets horrific mileage, no matter what you do. I gave away a 1967 Ford pickup, with a brand new engine, because it got 11 mpg, cold, hot, loaded, empty, it did not matter. It just got 11 mpg, no matter what I did. I have an 89 Civic Wagon, which I have about $1000 tied up in. If I drive it reasonably, I get 35+ out of it. If I drive it hard, I get 30+ out of it. It costs $35 to fill it, now, but I can still drive 325 miles or so, before I go to the gas station.

With the car you have, you can't improve the mileage enough to recover the cost of anything spent to improve it's mileage. You need to lay out a plan to dispose of it, or you need to accept its lousy mileage as a price for owning it. One or the other?

The quarter deal works a lot faster than you'd think, seems hokey, give it a try.

Few thing you can try. Start by making sure the car is in good mechanical shape (plugs, filter, etc). Inflating your tires to max sidewall pressures for less rolling resistance. You can go with a grill block. They are cheap to make and easy to install that will help the engine warm up faster. Look at your route and see if you can find another way that does not have as many stop signs etc. If you have flexibility leave earlier or later sometimes 30 minutes to an hour can make all the difference in the world. Here's a thread on driving tips. As always the biggest improvement will be with driving techniques if you're not getting up to speed. :turtle: Welcome to the site.

Welcome to the site! I was just a bit younger than you when I first got into this stuff, no I'm SO MUCH OLDER (19, :p). Good to see you taking initiative though.

If it were me I would do the best with what I had while trying to save a dollar a day from lunch money or eating pizza on the weekends until that + selling the current car could get me a little civic, crx, or metro. Keep your ear to the ground, because every so often they go for almost nothing.

Welcome aboard.

Hey, Your not the only one driving a honking vehicle :p there's us truck and SUV drivers too. If your like me, you just can't bear to sell the vehicle you fell in love with >.< if you get a geo, you could save gas by driving it, then use that money to fix up the Merc the way you want it, and use that for a cruiser. Once I get enough to buy a geo, I'm gonna drive that everyday, stop puttin the miles on the jeep, and use it for recreation. I found a geo for 650 yesterday, so you can def. find them cheap.

aha, you're still not worse than my car ;) and if I want to, I can easily get 10-12 mpg if I drive stupid hard. Im trying right now to get this week above 20mpg, so heres to hoping.

by the way, those 5.0s were known for completely clogging to egr screen, which leads to some performance problems but really hurt gas mileage as well. Ask a good tech in your area, they should know what Im talking about. Its like a $10 part.

for your Evo should easily get over 20mpg's. it's rated at about 25 highway (old EPA) right? It's a 2.0L w/ a turbo. If I can get about just about combined EPA for what it's OLD highway EPA is rated at w/ a 4.0L I6, you can do it with yours.

You don't even wanna know what I can do if I drive stupid hard, If I floor it to 60, Gas gauge goes down about 1/8th tank, and that's with 23 gallons :D

A big difference from the Mustang 5.0 to the grand marquis 5.0 is exhaust limitation, your diameter from the down pipes back to the muffler are considerably smaller than the mustangs 2.5 to 3 inch exhaust , next time you need a exhaust system replacement , think of a dual exhaust system , you can pick them up for around 200-250 through summit , or 300-400 through flowmaster, if you dont stand on it all the time you will notice around a 2-3 mpg improvement, also mustangs weigh a crap load less than the grand marquis you at about 3775 curb weight and the mustang is 2775

easy mods
 

At 125k miles you are overdue for changing the rear end lube. Replacing this with a good synthetic gear lube will make a measurable difference in mileage. (hypoid gear sets have lots of friction)

Motorcraft 5w30 synthetic blend oil (really cheap at Walmart) in the crankcase should help a little too.

If your cooling system fan doesn't have a clutch, then adding a fan clutch adds a little bit to your mileage. Of course you could always add an electric fan, but that is much more involved than simply adding a clutch fan setup.

I second setting the air pressure in your tires higher than the Ford recommendation. My personal vehicles are usually set 10% higher than the manufacturer's recommendation, but some people go even higher.


Good luck with your car!

Wayne

wow, i wish Malibu1 got 15mpg on the highway

try 11.8mpg average on premium, then you got problems, lol

Try checking the tranny fluid - if it's old and cruddy, it isn't doing you any favors. Have a reputable shop do the job right - don't go to Jiffy Lube or some such, take it to a dealer.
The jury is out on Slick 50 for most folks, but I'm sold. I trust it. Do an oil change with Slick 50; 3000 miles later change to Mobil1.
Check your front alignment. In fact, you might want a thrust-angle alignment while you're at it - I see some of these older Fords doglegging down the highway, they're just scrubbing their mileage away.

Honestly, the car looks great. Sell it and drive something more appropriate. If it's doing as well on the highway as you say, then pawn it off on some ol' duffer who doesn't have a regular in-town commute anymore. The GMarq is about 50% more car than you're likely to need, though I don't know anything about you or your lifestyle. But for a young'un scooting back and forth to school and work, a GMarq is, well, kind of fuddy-duddy. Get yourself a good used Golf, or a Jetta. They weigh a lot less and you might get lucky and find one with a diesel.

its tough to beat a car that's paid for, pencil it out.
40+psi tire pressure, syn. lube in gear boxes, set base timing to 12 degrees, single exhaust, new filters, try with and without EGR(if its stuck open real bad for mpg) some respond and some don't, Vacuum gage, check brakes for drag, esp. e brake cables, straight alignment, you probably have a great rear axle ratio, best mileage is drive fast enough to just keep the Torque converter locked up, sir coast alot, drive like you have no brakes (look way ahead as far as you can see), shut off if long wait, small fan on dash much better than AC, intake and exhaust mods won't help unless something is bad, because your only using 20hp (right), neutral coast with engine idle, drive like who, vacuum gage, careful with a grill block can damage things under the hood, and last but not least,
add one item at a time.

As I've only got a few minutes, I'm going to post what I can before I have to take off.

First: I cannot sell the car for financial and other reasons. I can't get enough out of it to buy anything even remotely better; in St. Louis cars like this are worth $500-800.

EGR screen has been cleaned, found out that issue a year or two back.

I have considered a new exhaust; I'm looking for one off the '87-91 Crown Vic Police Interceptors from a junkyard or other inexpensive place.

Tranny fluid has been replaced. Planning on a full flush at some point. Alignment was fixed by the previous owner, but (lol) they did it with the steering wheel off-center :confused: So now, to go straight, the wheel's turned about five degrees left. I'm used to it, though, so not a big issue.

It does have a functioning fan clutch. That may be replaced whenever the radiator completely goes; I figure that if the radiator's going to be out, I might as well change the clutch there while I'm at it.

I'm not driving to and from school...I'm homeschooled, so all I really use this for is driving to work :)

Grill block is not in any way possible. I've got a leaky radiator, and it runs a tad hotter than I'd like anyway, though still far under red line.

There is no brake drag. The thing coasts for about ten miles when I let off the gas at 55mph. And yep, it's got a 2.73 rear axle(not-limited-slip). From my figures, the engine runs somewhere around 500rpm on the highway :eek:

I actually HAVE to drive it in Drive instead of Overdrive around town, as otherwise it shifts into overdrive by 30mph and runs the engine so slowly that it instantaneously stalls. No joke. Once I'm up around 50 or so though, I do shift it into OD.

Since I just noticed and read the post about driving techniques, it's at the end.

I do drive highway about 80% of my commute. I take the shortest route to the highway, and I get off about two hundred feet from my job. I drive smoothly, and only go fast enough to keep from being run over by the crazy 18-wheelers :rolleyes:

robbie, sounds like you doing very well for 17. I couldn't think of a better car for a young driver. The open exhaust will not help mileage unless the cat is or muffler is plugged. Your are not putting much HP thur and it's made for 150. Your radiator is you primary concern. Check places like Advance Auto for a rad. around $200 is good. Sooner the better if the anti-freeze hasn't been changed. It doesn't sound like the transmission is working properly. Check if the kick down cable or rod is adjusted correctly. Some have this method and some do it electronically. Should not stall in automatic. However in slow traffic, you are correct in shifting into direct drive so that the converter can stay locked at the lower speed. Also check that the converter is unlocking when its suppose to. To save money learn all you can. Read my previous post carefully between every comma is different idea. Your car is capable of 20+ MPG. And we haven't even got to aero mods, but no need if your driving city. I wish I had your rear axle. Keep good records. Let us know how much each idea helps.

Why pay someone else to change your oil and tranny fluid :rolleyes:. The money used for labor could buy a nice vaccum gauge or something. I know how ya feel about sellin' the car man. If it's paid off, why the heck sell the thing for not enough money to buy something else, pay monthly payments for a short while so you have something to drive, and have to start over from scratch fixing problems that you've already fixed on the last car.

Haynes makes excellent how-to books on stuff like tune-ups and replacing parts and such. Pick one up if you need some guidelines to do work. Very helpful.

As far as the tranny, did they make band adjustments and stuff when they changed it (fluid) last?

Welcome to the site. Try the links below for radiators. I haven't personally used them, but have heard good things about them. Looks like a reasonable $118 with shipping, not bad.

Radiator w/ AC

Radiator w/o AC

Radiator isn't leaking a ton right now, perhaps a quart a month. Since it's buried under a mound of stuff in my car, including electrical equipment and other things, and since I don't have a whole lot of experience with cooling systems, I'm going to have the local mechanic put it in. I know him pretty well, and he'll give me a good deal installing stuff that I already have.

I change my oil every 2,500 to 3,000 miles. At the moment using whatever the cheapest stuff Walmart has...after 15 years of non-synthetic, I'm not sure synthetics would do much good for the cost involved with filling it with them. It takes a LOT of coolant :p

Rear axle causes some issues in the rain--live axle, no limited-slip diff, and massive torque mean I drive sideways when it's wet! At least I'm getting good experience if I ever want to go dirt-track racing :rolleyes:

Kick down cable is adjusted properly. I've gone over this car, replaced quite a few things that went bad or were just toast(two alternators, wiring harness(mechanic), brakes, tires, HVAC controls, patched rust in rear fender, various gaskets, hoses, belts). It may need head gaskets in a year or two due to coolant leakage, but it's low enough now that from the experienced people I've contacted, it's good for a while. Holds compression nicely. Only problem is that it hates St. Louis' summer "oxygenated gas"...runs extremely poorly due to lack of oxygen in the fuel. If I go out of town in the summer, I get 20mpg...on St. Louis gas, 15mpg :eek: It'll get close to 20 around town in fall and spring, if the temperature is above 40 and below 80. Unfortunately, that's about 5% of the year here :p

sounds good robbie, keep practicing your driving technics later

for big 125,000 car your not doing bad. go to the library and get a ford book and a dummies car book. check what you can. look at timing and erg first. no first pull the plugs and see how bad they are. use the books