Gas Mileage for '73 240Z

[atomrat]

I was not sure where this should be posted, so I posted it here.

I have a stock '73 240Z, I was wondering what kind of gas mileage I can expect?

I have not started to drive it yet. Still have to get the gas tank repaired.

[John Coffey]

I would guess low to mid 20s on the highway.


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John Coffey
johncof@veriomail.com

[SoCalZ]

My 73 240 all stock 173,000 mi. is getting about 26mpg combined city and highway.

Originally posted by atomrat:
I was not sure where this should be posted, so I posted it here.

I have a stock '73 240Z, I was wondering what kind of gas mileage I can expect?

I have not started to drive it yet. Still have to get the gas tank repaired.[/QUOTE]

[This message has been edited by SoCalZ (edited 08-11-2000).]

[This message has been edited by SoCalZ (edited 08-11-2000).]

[visionary]

I have a '73 with no smog, 72 SU's, stock intake and exhaust('72 manafolds) and I get between 18 and 22 combined depending on my mood and the density of traffic. I have gotten as little as 16 and I always use premium gas. I have also changed distributors to a single point and removed all advance retard switching units, thermo couplings and wiring for the auto(rebuilt) transmission with impressive performance enhancments. Will need to rotate tires soon...

[genbean]

Hearing what you guys have to say makes me jealous! I have a completely stock 72 240z and im getting around 14-15mpg city/highway mixed. Perhaps im running a little rich? The car runs fine except i have to get it pretty warm before i can let off the choke. Normally I have to drive it around for 10 minutes with the choke out so it wont bog when accelerating. I have a crane xr700 electronic ignition and a p60 coil on the way to my house via ups right now. Hopefully this will help some. I'll have to change my mixture settings. BTW I just got the car a couple months ago and i love it, except for the really crappy wet traction. My suspension is shot anyway...

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Ben

[Z-Priv]

Originally posted by genbean
Hearing what you guys have to say makes me jealous! I have a completely stock 72 240z and im getting around 14-15mpg city/highway mixed. Perhaps im running a little rich? The car runs fine except i have to get it pretty warm before i can let off the choke. Normally I have to drive it around for 10 minutes with the choke out so it wont bog when accelerating. I have a crane xr700 electronic ignition and a p60 coil on the way to my house via ups right now. Hopefully this will help some. I'll have to change my mixture settings. BTW I just got the car a couple months ago and i love it, except for the really crappy wet traction. My suspension is shot anyway...

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Ben

Sounds like you have the exact same car as me.. :) only had mine a week, but it also takes about ten minutes no matter what before i can turn the choke of.. which isnt to bad (until i forget about it being on), will probably have to change spark plugs more often, but would like to fix it. Could you send me a message if you get yer problem fixed? i'll do the same if i get mine fixed. Was thinking of adjusting the carbs, but i realized i didnt know jack about them, will soon enough... I love the car, i wish i would've bought one sooner..
http://www.240z.org/forums/showthread.php?s=&postid=2683#post2683 (http://) pics of car.

[v12horse]

Hmm, I am getting really bad gas mileage. I was wondering if you guys could pin point my problem.

engine specs:

-no smog equip
-oem electronic distributer (10 over and a 36 max. I am not sure what that means)
-msd blaster coil.
-my mechanic convinced me to use 20w50 oil. I think I am going to change back to 10w 30.
-72' SU carbs
-oem exhaust manifold
- I do have ac, but I hardly use it.

The car drives great, but I get 13-18 combined driving and I am getting 10mpg city. I love the car, but I hate to fillup as much as I do. It was not this bad before I had the work done on my car (exhaust manifold, new coil and distributer, oil change, and removal of air tube.)

please help.

-Ben

[v12horse]

ooops... repeat

[Hrududu]

Wow, you guys all do pretty good. I would have figured my EFI would do better than the old carbs, but I only get 17mpg tops on a good day.

[sblake01]

The highest reading I've achieved in my 78 was 27.53 and the low is 19.08 under normal conditions. It dropped to about 17.5 when I had a bad EFI relay and 16.8 when I had a bad cold start valve. I know this thread is about carbed cars but I was responding basically to Hrududu

[george71z]

My triple Webers get 18 on the Interstate. Never calculated the in-town mileage. However, on a road trip to Atlanta, my friends 72 with the SU's got 1/3 better mileage than me. We were travelling together; if I got 12 gallons at a gas stop to fill up, he got 8.

[beandip]

With my old L-24 with many miles on her she clocked a steady 23 on the hiway and 19 to 20 in town. All stock engine accept for a '79 ZX ignition and Round tops with F-54 needles . '73 Z automatic . v12horse , What air tube was removed ? Gary

[EScanlon]

Not being a mechanic, but knowing enough to be dangerous, could your mechanic have suggested the heavier oil because your rings/cylinders are worn and you're loosing compression (hence power) that way? Then again, the heavier oil will require the engine warm up more before it flows better and meanwhile that causes drag, which can reduce your mileage.

Keep in mind that you're getting opinions, all based on "what it SHOULD do" based on everyone's prior experience, and not what YOUR car should or IS doing.

For that matter, you need to address some of the more important basics. Have you had a compression check done on all cylinders? Have you had the valves adjusted? The carbs tuned and matched? Is the clutch slipping? Is the rear-end differential properly lubricated? Are the brakes adjusted properly?

Some of these may seem far-fetched and even outlandishly inconsequential, but you'd be surprised what even small adjustments can do.

Give the real mechanics (not I) a little more info and I'm sure they can give you a better opinion / suggestion.

Enrique

[Arne]

As an additional bit, I've seen several places and people who say that 10W-30 is fine for most climates in an L series engine. 20W-50 might be part of your problem. While I haven't got any experience with the Z yet (not ready for the road), I did have a similar issue with my family car, a '96 328i. Shortly after I bought it, I changed the oil and used 15W-50 Mobil 1. Lost 3 MPG on the highway. Changed to Mobil 1 0W-40 and the mileage returned to the former numbers. FWIW...

[Zup]

You may remember a member, named JPD here on the forums, that had a dark green and tan # matching 2/72 240Z (all stock) and a 7/70 # matching yellow and black 240Z.
He put them up for sale in the classifieds and I drove up from Arkansas to Chicago 2 weeks ago and bought them both.:classic:
The 7/70 is all in parts and was trailered.
The 72 I drove back about 675 miles and got 22.4 mpg with a heavy foot on I-44. (80+ mph often):surprised
Mixed it up with a BMW 3 on a divided section near Pacifica, Mo. for about 8 miles. :rambo:
He gave up. :smoke:
No tuneup or anything---I expect it will get better with a little massaging.:D

ZZZZZ's = great fun !!!!
"Zup"

[sblake01]

JPD is still here and active.

[nwcubsman]

...snip..., What air tube was removed ? Gary

Possibly the tube(s) that the smog pump uses to pump air into the exhaust manifold. Man, those were a b!t@h to get out of mine. The only stock part, I couldn't keep. Had to cut them in pieces because of the heat in the exhaust manifold. Just a thought.

[gogriz91]

Is there an overflow/fuel return system to pump unused fuel from the carbs back to the tank? Is there such a thing as unused fuel in an SU setup? The reason I ask is I smell raw gas right after I shut the car off and wonder if the SU's are just tuned really/too rich or is there a return hose that is leaking or missing.

[kenz240z]

Yes, there is a fuel return sysem on th older Z's. All the '72 FSM says is "This is a device which prevent vapor lock or percolation and to ensre a constantly stable idling in a hot engine compartment." I'd give all the rubber hoses a once over. Also check the hose that connects the float bowl to the jet at the bottom of each carb.

There is also a flow guide valve mounted on the inside of the driver's fender that routes fuel vapors from the expansion tank (located inside the rear passenger side plastic panel) into the crankcase. You might check those hoses as well. The flow guide valve has three ports: one to the crankcase, one from the fuel tank and one from the air cleaner. They are labeled C, F and A, respectively.

[gogriz91]

Thanks Ken, I appreciate it.

[Mat M]

V12Horse,

Have you solved your problems with the milage (if that was a problem for your car)?

Check out this thread on easy tune-ups:
http://www.classiczcars.com/forums/showthread.php?t=20319&highlight=float+bowl

Ensuring the correct float height will allow for a better fuel delivery to the carb.

Good luck!

[moonpup]

Originally Posted by EScanlon

Some of these may seem far-fetched and even outlandishly inconsequential, but you'd be surprised what even small adjustments can do.

Don't forget;

A) Proper tire pressure
B) Clean air filters
C) Correctly gapped spark plugs
D) Amputated lead foot...(Optional):eek: