Totallyrad

Guys, I need a little help. I've got a buddy with an 02 1500 QC with the 4.7 V8. He's getting about 12 on the highway, worse when towing his bass boat. He's not hard on the truck, mature driver. I'm not up to speed on the gasser stuff so who can tell me how to improve the mpg on this truck?

Mud Ready

Its just the nature of the beast. Theres not really a whole lot you can do to help mileage.

I tried all kinds of things on my Regular Cab 2000 Ram 2500 with the 360 when it was stock and couldnt hit 12 mpg. It now gets 6-7 mpg.

I tried the K&N air filter, high flow exhaust, tune ups, M-1 intake manifold, new injectors, etc., etc. and none had any affect at all on gas mileage.

Joe T

Something's wrong with the truck.. Should get 15-16 mpg.

steelblitzkrieg

Something is wrong with it? Bad 02 sensor maybe? My 02 QC 4x4 5.9 gasser gets 10.5 city and I can eek out 17-18 highway at 60-65, If I hit 70+ it drops to 14-15, and drops real quick from there. His 4.7 should be better than mine, his is better technology.

How many miles on it? I have 60k on mine, 10k on new motor, every gasser Dodge I have owned had the 02 sensor fail around 70-75k and my fuel mileage went down. One I never even got a check engine light,my moms Saturn and her Dodge Shadow were the same way...70-75k and the fuel mileage started to drop, but no CEL.

steelblitzkrieg

P.S. Have him check his codes by cycling the key.

Totallyrad

I don't know the mileage on the truck and I will get him to check for codes. He's got a buddy with a similar truck and engine combo that claims he gets 20-21 on the highway. I think that's a stretch but 17 should be real world numbers IMHO.

steelblitzkrieg

I would think it should be the same as mine, smaller engine = more effecient, but has to work harder = more fuel.

I'd almost put money on the 02 sensor, I change them at 60-70k now as part of the recommended services. They're cheap enough and easy enough to do anyways.

steelblitzkrieg

Just checked Dodge...

4.7 4x2 Manual 16C 21H
4.7 4x2 Auto 14C 19H

4.7 4x4 Manual 14C 18H
4.7 4x4 Auto 14C 18H

Joe T

Few things to do quickly. Check the maintenance intervals and make sure he isn't missing somethign. Then make sure all the fluids are full and clean not burned. Change the air filter and make sure the box isn't clogged, just get a paper one from the parts store. Check the engine bay to see if anything has come unplugged or is jarred... Quicklube type places are notorious for not putting things like airboxes back together right or accidently unplugging sensors.

If it runs noticably better drive it and check it again. If not maybe pull the o2 sensors and spray them with carb cleaner just for the hell of it to see if it runs better. We did this with my brother's chevy truck and the check engine light didn't come back on again for a failed o2 sensor and it ran better... But we knew which one was bad to begin with so we didn't mind taking a chance with it, it took a couple tries but worked like a dandy... He sold the truck awhile later without the check engine light coming back on and $80 still in his pocket.

Besides that on the Hemi there is something you have to clean like the PCV or something? It isn't replacable you just clean it although I never did it because it never gave me any problems... On my Hemi the plug intervals were 30K miles , I changed them at 38K and they looked good IMO... Don't know why they required that so soon since it is 16 plugs. They wanted 250 at the dealer so I did it myself.

Totallyrad

4.7 4x2 Auto 14C 19H.............That's the one!

MikeyB

Over on the gasser forums it seems with the newer engines installing lower gears help with the fuel economy. Quiet a few Hemi owners are switching to the 4.56 gears for both power and economy (especially with the 20" rims).

MikeyB

steelblitzkrieg

4.56? Geez? Where are the running, Martinsville?

Mine is 3.92 (IIRC) and it came with 20's on it, I would think that 4.56 would kill the mileage, although they do have 5spd auto's.

I don't get the changing especially for 20's though, the overall size is still the same, mine has 32.01" overall tire 305/50-20, practically the same as my 17's on the 2500, the 265/70-17 = 31.62".

ckt_santiago

20's have more mass so the laws of inertia will affect them more in that it takes more energy to get them rolling. With lower gears it takes less to get rolling and you will accelerate faster with less throttle/engine load. So for city driving it's a great idea really. Though highway mileage really takes a hit

Truckman0097

That's right - the weight of the wheel definitely makes a difference....

I would have to say there must be something wrong with this guys truck - My old Dakota with the 5.2 got better mileage than that, and I used to have a brick for a foot....

steelblitzkrieg

Aren't most 20's aluminum vs most 17's being a chromed steel? And wouldn't less tire mass also help to offset that?

You're going to make me remove a wheel from each of my trucks and weigh them, aren't you?