Gas Mileage: 413

[denisondc]

Sent: 10/29/2003

I have a D22 with the 413 engine and a 4.56 rear axle ratio; it weighs 5 tons. I have been getting close to 8 for several years, like 7.8 and 7.75, over the 4000 miles we drive each year, from Northern Virginia to Mexico and back - i.e. no big hills on the drive. And one year we got 8.01 mpg.

I only try to go 55, or maybe 60 to avoid bottlenecking the truckers.

With the 318 you might get more than 8, perhaps 8.5, but so much depends on the speed you travel, the terrain you are in, and of course whether you are towing a dinghy.

The rear axle ratio makes a difference too. For certain years the 318 came with a higher rear axle ratio than the same chassis and wheelbase would have had with the 413. The ratios included 4.10 in 70 and 71 I think, and 4.56, and 4.88. The 4.88 was mostly on the M500 and heavier chassis, i.e. RVs over 24 ft long. Thus they would get lower mileage cause the engine was turning more to cover a mile.

And the 440 displaced a little more air, so mileage would suffer a bit. denison

[kevsws6]

Sent: 10/29/2003

Denison I have a punched out 413 that I get 7.5 to 7.8 with it all the time. It also has 4.56 gears. That is towing a 12 foot trailer with 3 quads up over the 8 pass on the way to Glamis. I drive 60 to 65.

When I drove with dad I was doing 50 to 55 without towing anything.

[Elksnoutmtman]

Sent: 4/10/2005

I have a 21' Brave with a well tuned 413. Anyone know what I should expect for gas mileage? I like to drive about 60 mph, just to say I baby it.:}
Any help would be appreciated...
Thanks DON

[denisondc]

Sent: 4/10/2005

I have a 72 D22 with the 413. I aim to get 8, usually have to settle for 7.6 - 7.8. I usually cruise at 55 mph, a little faster if the heavy trucks are running at 60, a little slower if Im the only thing on the highway. I may advance my idle timing to 8° btdc and see what happens.

[Elksnoutmtman]

Sent: 4/10/2005

Thanks for answering.  I was wondering if it might make more sense to run a bit slower. Speeding up with trucks is probably a good idea too.
Let me know how the 8* works if you try it.
I saw something about that on one of the other discussions. I'm at least curious about it with gas prices go up so high.


DON

[denisondc]

Sent: 4/10/2005

Driving slower would give you better mileage on Level roads at steady speeds. But... In hilly country your mileage will depend on your ability to anticipate hills, to arrive at the bottom of an upgrade with extra speed, and crest the top at a lower speed, gaining it gradually back on the down-slope. This doesnt work in a steady stream of Interstate traffic unfortunately. No one appreciates you changing speed as they pass you and get passed by you.
Some people have installed a tbi injector system, in place of the carb, but I dont recall that they gave us feed back on the mpg improvement. Telling us that it starts better and runs stronger or smoother doesnt help much. The same things might be true if they just installed a new carburetor and fuel pump in place of a leaking cruddy old carb that badly needs rebuilt, ie. more than 6 - 8 years since the last rebuild.

Ill try to remember to give the result of advancing my ignition timing a couple of degrees. I wasnt happy with the color of 3 of my 8 spark plugs last year. Too dark.

[mightybooboo]

Sent: 5/8/2005

You know,Ive had 427, 428, 429, 440, 454, 455, 460,and 472 cubic inch motors in  cars.I  dont  think Ive ever got much more than 8-10 mpg in the real world.  Bigblocks just pretty much mean 8 mpg or so, uphill, downhill, tailwind, doesnt matter much in a car, and they are more aerodynamic than a winny will ever be.

BooBoo

[JCMAC]

   
Sent: 9/15/2005

HI,
  In my '72 D22C, I get 6-7 MPG.  I tow a Jeep Cherokee (3100#) like it wasn't there.  7 MPG on cool days, on the flat at 55 MPG.  Remember the HP goes up with the cube of the speed [2X speed = 8X HP....or 65 vs. 55 = 1.65X the HP] and a noticeable reduction on MPG!
  I got Doug Thorley headers - BIG difference, 5-6 MPH more on those big grades and 1/2-1 MPG better.
  Then added a Edelbrock aluminum intake (Performer 440): added 1-2 MPH on hills and a tad better MPG.  I'll let you know how my Edelbrock 750 CFM does.
John

[moparmotivator]

Sent: 4/28/2006

Just got back from a 1300 mile round trip to Galveston, TX.
My average for the entire trip was 8.9 MPG.  I ran 65-70 most of the time and had the generator running with 1 ac unit on all but about 200 miles.
We bucked a strong headwind going south and a light headwind coming back, we hit the cold front that dropped all the way to the Gulf on the way back.

I am running a 413-3 with a quadrajet and free flowing dual exhausts in a 73 Travco 270 with the M400 chassis.

I am not sure of the gear ration, 70 mph puts you at about 36-3700 rpm and 12-15 inches of vacuum on the flats, I tried to keep the gauge over 7 inches.  Overdrive would be nice.  I think it would run 100 as is if you had the nerve though.  I was able to easily stay with faster truck traffic on the interstates.  I can't imagine running 55 mph on the interstate these days, you would get sea sick from everyone passing.

Also running Michelin XCA 17 inch radials at 75 psi.  Those tires are really narrow and roll nice.