fuel economy could be better?

[mattchew]

So anybody here have any ideas as to how i could get better gas mileage outta this car of mine? I drive about 20 to 60 miles a day. (pizza delivery) I'm not sure if it has something wrong with it or if its just normal but the car only gets 14 mpg in the city and 18 on the freeway. Here's an overview of what i have, 1972 240z with stock 2.4 liter, 4 speed tranny, stock dual S.U.'s (tuned by Steve at Ztherapy), and r180 rear end. Runs great and tranny or clutch doesn't seem to be slipping, but it needs an alignment and the rear end clunks and i think it should be a little faster. Here's what I've done to it so far. Tune up--- New Plugs/wires, K&N air filter, 280zx Electronic distributor, Electronic fuel pump, i think the oils 10w 30. new alternator, gas tank, front body kit, fuel lines cleaned. any ideas would be greatly appreciated:)

Edited December 1, 2011 by mattchew

[madkaw]

Alignment can effect gas mileage. Whats your timing set at and is your vacuum advance working properly?

[5thhorsemann]

I think you are right in line with those numbers, my 73 gets similar city milage, but way higher highway, like 22 or 25 MPG. If I don't "drive it like I stole it", I get even better.

[SteveJ]

Alignment, inflation of tires, short-shifting (aka granny shifting), easy on & off the gas. Check your mileage after that. If you want to go deeper, research using a carbon monoxide meter to tune. All other factors being held constant, minimize CO = better fuel mileage.

[mattchew]

I think i retarded it 8 degrees, after putting the electronic distributor in it. Oh and could adjusting my valves help? someone suggested that. oh yea i forgot to put that, the vacuum advance is a little weird. it has like a hundred rpm variation at idle speed. maybe i should get the distributor rebuilt. oh and yea i kinda drive it quick, not too crazy though. i shift at like 3500.

[Zed Head]

You should measure and set the static timing, and confirm that the vacuum and mechanical advance of the distributor both work correctly.

The later 280ZX distributors are designed to run with EGR and have a lot of vacuum advance. You might have to dial back the static timing to avoid knocking at partial throttle (where you'll be driving for economy). The first thing you should do is determine exactly what distributor you have and measure and set your static timing. The 79 ZX has a pretty good setup, the later ZXs get more complicated. What year did yours come from, or what is its part number?

Your jumpy timing at idle could be because the vacuum advance vacuum hose is direct to the intake manifold instead of a ported source.