Fuel Mileage

[john h]

I'm running the Fitec EFI with the ignition control. the car runs really well.  It starts great.  I made a few long runs of 50-60 miles a number of times and some around town driving to get it to learn.  Now I went on a 130 mile run.  mostly 60 MPH driving no hot roding.   just cruising on county roads.  I checked my mileage and I"m only getting 14.5 MPG.  I don't know that i ever paid much attention to it before because I rarely checked the mileage so I don't remember what it was getting with the carb.  It's a stock 360 crate motor 300HP version with 3:55 gears and 727 trans. The brakes don't drag and I have 17" tires on it.  the AFR is typically running around 14.2-14.6 at cruise speeds and at 55 i'm turning around 2600 RPM.  I feel like I should be getting close to 20 MPG.     what kind of mileage do others here get?

Thanks
John

[1 Wild R/T]

Maximum fuel economy in a muscle car requires being bored to tears... I've pulled down a best of around 15.5 coming home from Spring Fling but it was 300 miles of 55 MPH.. Boring!!!!   I say suck it up & enjoy the drive.... 

[cudabob496]

if getting 14.5, you were previously only getting 11 or 12 mpg.
Can get better milage if you use synthetics in engine, tranny ,and rearend.

[cudabob496]

Also, I made a front air dam connected to lower front valance.
Keeps turbulent air from going under car and increasing drag.
May ways to impove milage, but will never be by much.

[rUNCHARGER]

The 3.55's are hurting it. I know lots of people love those gears but I hate them. They aren't good at anything. I like 3.91/4.10 or 2.94/3.23. What camshaft is in it?

Sheldon

[GoodysGotaCuda]

I'm running the Fitec EFI with the ignition control. the car runs really well.  It starts great.  I made a few long runs of 50-60 miles a number of times and some around town driving to get it to learn.  Now I went on a 130 mile run.  mostly 60 MPH driving no hot roding.   just cruising on county roads.  I checked my mileage and I"m only getting 14.5 MPG.  I don't know that i ever paid much attention to it before because I rarely checked the mileage so I don't remember what it was getting with the carb.  It's a stock 360 crate motor 300HP version with 3:55 gears and 727 trans. The brakes don't drag and I have 17" tires on it.  the AFR is typically running around 14.2-14.6 at cruise speeds and at 55 i'm turning around 2600 RPM.  I feel like I should be getting close to 20 MPG.     what kind of mileage do others here get?

Thanks
John

So at 60mph you are around 2,700rpm, if you could get that cruising RPM down to 1,700 or so, where a V8 will be more than content...you will see much better mileage. I expect 20mpg out of a double-overdrive 6spd and a 3Gen Hemi.

[HP2]

I think you are about where it should be given the nature of the 300hp crate engine. You might get a few more mpg with all synthetic lubes and then a few more with an OD trans. So if you go from 14 to 20 mpg for $5k in upgrades, is it worth it?

The best way to increase mileage is to increase cylinder pressure. Increased cylinder pressure uses the fuel mixture more efficiently which means you need less fuel to produce the same power. IMO, biggest fuel mileage and power gains come not from playing with transmissions, gears, and tires, but maximizing piston and combustion chambers interface in the engine.

Case in point, I had a 440 in my truck with a three speed trans, 4:11 rear, and a carb that could routinely knock down high teens pulling a load down the highway. It was nothing trick to look at, but had its induction, compression, exhaust, and ignition tweaked within an inch of its life.

[Mopar73340]

I think your doing pretty good running that kind of rpm. I have a 340 727 with GV and 3.23's and average 16-17 combined if I keep my foot out of it.

[cudabob496]

I don't think we should be concerned about mileage, unless
its due to a real engine problem. Stay with those gears, or
half the new cars on the road will kick your butt.

[onebadfish]

I get a quarter tank to about twenty minutes of fun around town. 

[rockymopar]

I get 20-21 mpg with a mega squirted 360 Magnum, 3.23 gear and a lock up a518. When I had the same engine combo in front of a 727 with the same rear,I got 14-15 mpg. Sounds like you are in the ballpark

[Katfish]

Sounds like your right where you should be.
Did a 300 mile trip yesterday, got right around 18mpg doing 70mph.
340, 518 with LU, 3.73 gears
I was only getting 12mpg before the 518.
My 06 GT Mustang with 3.73 and 5sp auto only gets 20mpg.

[EMCD]

I took my SB 408, 727 tranny with 3.73 gears out for a romp in the mountains and got 8 mpg.... I was hard on it, but I hoped for better than.8...

[cudabob496]

a sure way to know if you are getting your best mileage is to install
an A/F ratio O2 sensor. Mine is always reading around 12.5 to 13.5, which is good
for a street racer.
When I first hooked it up, I was reading around 11.0, so I knew I had jetted the carb
too high.

[EMCD]

Where do you place the sensor? I was driving with my buddy in his '78 Z28 383 stroker. We had a roll on at 50 mph and I smoked him easily. I have to tell you, that felt great!