Im switching from a 225 to a 318, is there a big difference in fuel cost?

I am thinking about buying a 73 Dart that has a 318 engine in it. The only thing I am worried about is I have been driving my 75 Duster that has a 225 in it for the last year and it really has been good on gas. I dont want to switch to the 318 if its going to cost me a bundle every time I have to fill up. Does anyone know if there is going to be a huge difference in fuel price? I dont want to buy the Dart and feel like I cant use it as my daily driver because of how much money it will take to keep it moving.

If the 318 is stock, runs good, and has had a tune-up a 318 isnt to bad on gas! you might lose a couple mpg. may not lose any if you drive it easy, jmo!

He'll the 318 may get better mileage then the six if ya keep your foot out of it. Every post 70 six I ever had had no power and got horrible mileage. The mid 60's sixes I have always had good power and got way better mileage.

SCREW THAT! I GAINED MILEAGE!

In my '74 Duster;

The /6 I had was getting about 15 MPG Hwy on a good day.

I swapped in a '79 318 and LU 904 tranny along with a swap from the small 7-1/4 rear to a 8-1/4 rear with 3.21's and it's a sure grip equiped rear to boot.

The following engine mods still allowed for 18 Hwy. MPG's on a stock tire size.

Unsilenced air cleaner up top a 600 Holley and later a 625 Carter with no mileage loose there ethier.
The first intake was a LD4B and now is a OE 360 intake. Equal at this point in time.
Headers (Hooker) into a Jegs 2-1/2 exhaust and a Crane Cam, Hyd @ 050 216-228/.454/.480 on a 112 c-line and a electric fan, orange box fired through a OE vacuum advance distibutor.

She turns around 3000 - 3300 on the Hwy.

IF I crank up the timing, it'll need better than 87 octane but, 92 does it, it adds not only performance but it also added another MPG and a half.

(Currently last run @ 15.14 @ 89 mph on 87 octane)

No head milling, no larger valves, idles and drives to Grand-ma's likeing. Quick enuff to get on the Hwy or pass on it. The gears hold it back, but also keep it nice enuff to frive anywhere at anytime. And I do so.

Dump that 6!

thanks everyone! im glad I asked, i feel a lot better now.

What kind of mileage DO you get with your slant? I have never used my 318 as a daily since high school so I can't give any solid advise, but combined mileage of 15 out of a 318 dart should not be hard to achieve at all, even higher numbers if you put some time into it. The V8 isn't going to be as loaded up as the /6 all the time hence the better potenial of fuel mileage.

Dartboy52 said:

What kind of mileage DO you get with your slant? I have never used my 318 as a daily since high school so I can't give any solid advise, but combined mileage of 15 out of a 318 dart should not be hard to achieve at all, even higher numbers if you put some time into it. The V8 isn't going to be as loaded up as the /6 all the time hence the better potenial of fuel mileage.

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well im still getting about 18 mpg avg and my slant isn't even close stock :cheers:
u should be able to get upwards of 22-25mpg with the stocker 225

You will like the 318, in stock form it's almost 50% more HP then the slant with no real penalty in MPG. You should be able to add 100 HP to a stock 318 with simple bolt ons and if you run highway gears your MPG will be pretty much the same. My Dart is set up similar to Rumble's except I am running 2.76 gear, 600 holey on an old streetmaster intake, cam is stock 340 grind 210@.050 intake, 220@.050 exhaust lift I think is .429 &.444. Has a good tune on the carb and advance curve, runs 89 octane. Standard low comp short block duals with manifolds, factory high stall convertor and transgo TF-2 shift kit. Car has ran 15.4 and will get 20 MPG highway easy if you keep the speed down. It has done a best of 23 MPG on a warm day driving 55-60. I had an 78 aspen with the super 6 set up with bigger exhaust and a few other tweaks and it was hard pressed to get 20 on the highway and was over 2 seconds slower in 1/4.