MPG for a 1979 MGM

[Alex P. Keaton]

Hi everyone,

This is my first post. I figured since everyone here is familiar with the Fords, Lincolns, and Mercurys of the past, I might have some luck getting some answers.

I've been in the works of buying a pretty well-kept '79 Grand Marquis, but since I'm a student, the gas is somewhat of a deciding factor. I've tried many different websites and information sources out there, but fueleconomy.gov (which seems to be the most reliable one) only goes as far back as 1984 model cars. Their file database for older cars is outdated, since the miles per gallon on a new car in 1979 is going to differ in 2010. Now, I'm not too familiar with engines, but I do know the engine names.

Here's what I do know:

In 1979, the Marquis line was downsized from the previous generation boats. The Marquis/Marquis Brougham/Grand Marquis remained until 1983, when the car altogether was rebranded as the Grand Marquis and the Marquis name was passed down to the new Fox-platform Ford LTD twin.

Here's my question: assuming the '79 I'm looking at has the standard 5.0L 302ci Windsor V8 engine, how many miles per gallon am I expected to get?

Are there any problems that I should specifically look out for? These cars are brand new to me, and I have no experience or expertise on them (yet!).

What are the main differences between the '79-'82, the '83-'85, and '86-'91 Grand Marquis? I know that somewhere along the line, CFI and EFI came out... I regret to say that I have no clue what any of these terms mean. Do any of them make the car more desirable in terms of maintenance?

Also, an unrelated question: what was the difference between the '79-'82 Marquis Brougham and the '79-'82 Grand Marquis?

I know this is a long post, but I'd really appreciate your expertise on this one.

[Brandon]

Hi. Well your gas milage aint going to be so good. It is a big car. I'm guessing 15mpg to 16mpg at the tops.

The 79 is a bigger car than the 80. The 80 has a different grill and is a bit smaller. 83 they went to cfi and 85 they went efi.

[MattsLincoln]

actually 86 is when they went to efi. 84 started EEC-IV and 83 is EEC-III.

[1990LTD]

Ford likes Canadians more - They didn't give us CFI.

[ford man]

'79 has the 3 speed c4 transmission. Good because it's simpler and cheaper to rebuild. Bad because there's no overdrive for economical highway driving. If you don't drive highways much then no sweat. '80 was the first year for the overdrive AOD transmission. I wouldn't expect much better than 14 per gallon with a light foot. Insurance should be dirt cheap...

The power windows go out, but are easy to fix. If its clean and has a strong motor and trans go for it!

[gadget73]

That ought to be a 302/2bbl car. Probably mid teens but on the highway it may hit 20 or so. Rear will probably be some disgustingly tall ratio, 2.26 or 2.42 or whatever nonsense like that. The tall rear is gonna make it suck around town for pep and economy, but it will more or less make up for the lack of overdrive on the highway. The 2150 2bbl is pretty reliable, and fairly simple to rebuild if it needs to be rebuilt. The smog controls can be iffy, but as long as they are left alone, and all the vacuum lines are good it should be OK. If someone has halfass removed them, good luck. The C4 is mostly reliable. I hate how they shift, but they usually continue shifting for a long time, which I suppose is a good thing.


CFI = central fuel injection. Think bastard cross between a carburator and a fuel injection system. Its right when its right, but most people feel its basically a voodoo demon that does what it feels like doing. 1983 - 1985.

SEFI - sequential electronic fuel injection, aka multiport injection. This came out in 1986, and is generally considered to be an improvement for fuel economy, power, and reliability.

[Brandon]

Ohhhh... Good info! I still learn something all the time!

[86VickyLX]

Hi. Well your gas milage aint going to be so good. It is a big car. I'm guessing 15mpg to 16mpg at the tops.

The 79 is a bigger car than the 80. The 80 has a different grill and is a bit smaller. 83 they went to cfi and 85 they went efi.

No they aren't, they're the same size. 1979 Marquis was built on the panther platform, no bigger than the later grand marquis. 86 was efi.

[Tiggie]

Check out my History: http://grandmarq.net/tiggie/Box%20History/History.htm
All is correct as far as I know except I need to add in about the now verified Mercury Marquis Police Package.

The Grand Marquis (AKA GM) was the top of the line in 1979-1982. There were lower models like the Brougham and then a base Marquis. Basically the GM has lots of luxury standard features like better seating, carpet, insulation for a quieter ride, power windows, and a vinyl top that were options or not available on other cars. GM's also tended to be outfitted with more options like A/C, illuminated entry, AM/FM/Stereo or better, etc.

Standard was the 302-2bbl. Optional (and somewhat more common than in later years) was the 351-2bbl. If it was a US car, it will have the infamous Variable Venturi (VV) carburetor. If it's the 351W, it'll run the easier to deal with Motorcraft 2150. The VV worked well when new for most. With age, it starts to run rich (my solution was to tie to choke open with wire on my '82). The VV may have been replaced with a 2150 or even a Holley 2-bbl which wouldn't be a bad thing for you. In Canada, you got the 2150 with either engine.

I don't have 1979 EPA Mileage estimates. I do have 1980 LTD estimates (the same car, just a Ford), listed as city/highway MPG:
302/C4 17/24
302/AOD 17/26
351/C4 16/23
351/AOD 16/27
302/C4 (california) 15/21
302/AOD(california) Not available
351/C4(california) Not available
351/AOD(california) 16/26

I'd consider those high. I got about 13/22 in my '82 with 302/AOD. You can expect similar in town, and maybe 20 on the highway with a light foot and a good tune in the carb (pray for the 2150).

I'd take a 2150-carb'd '79 any day over a a CFI car. I consider the 302 carb/AOD package the best. But for daily driving, the SEFI of 1986+ is hard to beat. Just not CFI ever!

[gadget73]

No they aren't, they're the same size. 1979 Marquis was built on the panther platform, no bigger than the later grand marquis. 86 was efi.

maybe he's thinking Lincoln. 79 Lincolns were definitely bigger than 1980 models.

[1990LTD]

maybe he's thinking Lincoln. 79 Lincolns were definitely bigger than 1980 models.

79s were still barges in lincoln land.

[1987cp]

Hi. Well your gas milage aint going to be so good. It is a big car. I'm guessing 15mpg to 16mpg at the tops.

Well, it's more due to the fact that the engine hardware and management systems are crap rather than the vehicle being larger than some others, but the result is the same.

Incidentally, I often got near 20mpg with my '79 wagon, though that was with an '87 roller motor with an HO roller cam, Performer carb and manifold, and dual exhaust.

FWIW, with highway gears, highway engine RPM is still extremely low even with the C4. My wagon with its 2.26 gears could go 70mph in First without exceeding 5000rpm.

[85crownHPP]

actually 86 is when they went to efi. 84 started EEC-IV and 83 is EEC-III.

CFI IS (a form of) EFI

Those MPG guesses are highly dependent on IF the car is in decent running order...
This cherry isn't near central VA is it???

[Brown_Muscle]

302/C4 17/24
302/AOD 17/26
351/C4 16/23
351/AOD 16/27
302/C4 (california) 15/21
302/AOD(california) Not available
351/C4(california) Not available
351/AOD(california) 16/26

27 mpg with the 351...yeah right

[87gtVIC]

as I have heard a couple people here say...Smiles per gallon should be the only thing you care about.

I get around 12 MPG just romping around on the car around town, and get 20+ on the highways keeping it around 70mph. I recently drove to PA and back. 6 hours total of driving,,,over 320 miles and got 20 to the gallon keeping the car at 75 mph the entire way there and back.

I know fuel injection is a different animal but your car can do just as good on the highway as well.