Mpg....

[Tim 76' 280Z]

Hey thanks 76datsun280z. Gives me an idea of what i should be getting. My mpg should be a little lower cus i have an auto.

[JonnyRock]

According to my careful prosthesis (I track my fuel stops in an excel book), my mileage was affected a lot more by the weight of my foot than the kind of fuel I was using.

Your careful artificial limb? Did you mean "prosthesis" or analysis?

[Jehannum]

Your careful artificial limb? Did you mean "prosthesis" or analysis?

It was a little joke. It comes from this.

According to my careful prosthesis, you've got the plague!

[Jeff G 78]

I just took a ~400 mile trip in my Z and filled it up this morning. I got 25mpg even. 275 miles of that was highway and 50 was cummuting to and from work in rushhour stop and go. While on the trip I checked my odometer and it was amazingly accurate with my 225/50R16 tires. After 50 miles of watching mile markers, it was within a 1/10 of a mile total! My speedo is another story. It reads over 10% high.

[AndysPlit]

I just took a ~400 mile trip in my Z and filled it up this morning. I got 25mpg even. 275 miles of that was highway and 50 was cummuting to and from work in rushhour stop and go. While on the trip I checked my odometer and it was amazingly accurate with my 225/50R16 tires. After 50 miles of watching mile markers, it was within a 1/10 of a mile total! My speedo is another story. It reads over 10% high.

...maybe my mileage will improve after a valve adjustment.

[Jeff G 78]

There are a ton of things that could affect your mileage. Fuel injector spray pattern, air/fuel adjustment, rolling friction (bearings, trans, axle, brakes, etc), wheel alignment, engine wear, gearing... The list goes on and on. My car would probably do much better if I properly adjusted the air/fuel mixture. Right now I have a potentiometer in the water temp circuit to trick the system. I need to adjust the AFM, but it's running well, so I don't want to screw it up.

[AndysPlit]

There are a ton of things that could affect your mileage. Fuel injector spray pattern, air/fuel adjustment, rolling friction (bearings, trans, axle, brakes, etc), wheel alignment, engine wear, gearing... The list goes on and on. My car would probably do much better if I properly adjusted the air/fuel mixture. Right now I have a potentiometer in the water temp circuit to trick the system. I need to adjust the AFM, but it's running well, so I don't want to screw it up.

Right, a lot of factors to consider......But you think you can do better than 25 mpg? Damn! :cheeky:

[sleepyzzz]

i have worked out of my '74 260 2+2 several times this spring while we had cool weather to enjoy, since i don't have my a c working yet. i am around 220 pounds, and carry a catalog around that weighs 50 pounds, along with samples, other literature and such. as you know, the 2+2 is also heavier.

i leaned out the round top S U carbs almost to the point of making the car run rough, and the best i could get on hiway mileage was 26 mpg.

adjusting them just a little richer to give the car a little more power, and it runs much better, i now average 24 mpg. i do push the engine hard thru the gears, and i am sure that is not helping the mpg average, but man i like the sound of the engine running up the rpms. i have checked the speedometer and odometer against my watch and both are very accurate, running a mile a minute.

all of my smog controll items were removed in the rebuild. new bearings on all of the wheels, along with K & V round filters, and flowmaster muffler. i also swapped the tranny out for a five speed which i really like alot better. everything is new regarding plug wires, plugs, distributor cap, and such, and i don't know of anything else to try.

i was told by my mechanic that rebuilt the engine and heads to expect close to thirty mpg, but i don't ever think i will come close to that. i also tried both regular and premium gas and can't tell any difference in gas mileage between the two,although the car does perform better with the premium, as most stations around here still offer 93 octane.

[sblake01]

Best I ever got in my 78 was 27.8 on a trip to Solvang and back last year. I had cleaned the injectors and decarbonized the engine just prior to the trip.

[ktm]

Right, a lot of factors to consider......But you think you can do better than 25 mpg? Damn! :cheeky:

As stated earlier, I was pushing 30 mpg on the highway in my car with 3.54 rear gears and a 1978 5-speed. My AFRs when cruising are dead nuts on 15:1 and 40 degrees of timing (L28ET, 7.4:1 compression).

I am now running 3.70s with the Z32 TT 5-speed with a 0.75 OD. I need to replace my speedo with an electric one to figure out my mileage, but I expect similar results, maybe a little lower.

[snag point]

The last 3 fill-ups I have been watching the mpg. I've gotten 21, 20, and 19.5

in town with somewhat carefull driving. (very hard to keep off the foot off the gas)

[moritz55]

Here's one for reference point. I just tuned up my 4BL 390cfm Holley after installing a new ignition on my 240z. I also had a new clutch installed last week so my driving has pretty much 50/50 = highway/city and very light on the pedal since I'm breaking in the new clutch. I just topped off the tank after the tune up and got 20.5 MPG ! I'm pleased since so much of my driving was on the low end of the RPM/Torque range below 3000rpm and under 50 MPH. I'm anxious to take it on a small trip and get an better estimate of highway mileage. I'm sure my mileage will deteriorate as I push it more once my clutch is broken in. I included a photo of my engine setup and the specs below. Hope this helps.

Specs on my Engine:

- 2.4L E88 Head , P30 Block with Oversized Exhaust Valves (~9.5 : 1 CR)

- 4BL 390cfm Holley with Arizona Z manifold

- MSD 6A (pn 6200) Ignition box

- Mallory Promaster Coil

- Mallory Unilite Distributor

- Magnecor 8.5mm Ignition / Plug wires

- NGK's gapped at .058" -.060" (with the MSD 6A, I get great spark)