What did I get myself into... 98 Ram 5.9L ecomodding

[instarx]

Tires, not just inflation, make a huge difference in trucks. My 1-ton van mileage dropped by 3 when I switched from highway tires to M&S.

Those tires look new so I'm sure you don't want to toss them, but maybe you can get a set of summer highway tires to use nine months out of the year and use the current ones only as winter tires.

With a vehicle as heavy as yours, momentum is very important. The "never use your brakes" rule will do wonders for you I think.

If you tow, how are you going to do without that side mirror? That may have been a step too far. It looks like your mirrors will fold back - I might have started there rather than removing it altogether.

[Big Dave]

What I've found:

If you can live with a tonneau, get one. I had a flat tonneau and it was worth 1.5 MPG. Better yet, a fastback bed cover.

To help change the nut behind the wheel, install a pyrometer and a digital tach. For Ford (I-H) 7.3s the magic numbers are 2000 RPM and 600 degrees F EGT. The numbers should be similar on a 12V Cummins.

Since you are 4x2 maybe you can economically regear. I dropped from 3.73s to 3.08 gears. That gained me 3 MPG. But you have an auto and those gears may wreck your auto. I get away with it because I have a hand-shaker. Don't sweat the towing/hauling with 3.08s. My 7.3 tows Bobcats, macinery, and five tons of building materials just fine. No self-respecting Cummins jockey will admit the school bus motor is better than a 12V Cummins at low RPM.

A 4x2 can also be practically slammed, resulting in a 4 or 5 percent reduction in frontal area.

[ebacherville]

If you need the bed for ahuling but dont need tons of ground clearance, lower it..

[orange_eskimo]

Originally Posted by Big Dave

What I've found:

If you can live with a tonneau, get one. I had a flat tonneau and it was worth 1.5 MPG. Better yet, a fastback bed cover.

To help change the nut behind the wheel, install a pyrometer and a digital tach. For Ford (I-H) 7.3s the magic numbers are 2000 RPM and 600 degrees F EGT. The numbers should be similar on a 12V Cummins.

Since you are 4x2 maybe you can economically regear. I dropped from 3.73s to 3.08 gears. That gained me 3 MPG. But you have an auto and those gears may wreck your auto. I get away with it because I have a hand-shaker. Don't sweat the towing/hauling with 3.08s. My 7.3 tows Bobcats, macinery, and five tons of building materials just fine. No self-respecting Cummins jockey will admit the school bus motor is better than a 12V Cummins at low RPM.

A 4x2 can also be practically slammed, resulting in a 4 or 5 percent reduction in frontal area.

Thanks, I have thought about all three of those and tonneau cover will probably be coming with my next bonus.

Oh and its just a 5.9 gasser so no cummins jockey here.

Wish I had an update but Im only 1/2 way through my first tank on these mods so by next week we will see if they paid off.

[MechEngVT]

I feel your pain, I have a 2002 Ram with the 4.7/5spd. I'll second Big Dave on the tonneau as without crunching the numbers I'll say mine was worth more than 1mpg, probably would have a larger effect on a long bed (mine's the 6'-3 bed).

I think with your grille blocks you need to be most careful about your transmission fluid temperature. The auto Rams particularly the 2nd gens were very sensitive about ATF fluid temperature.

You're not starting out at a bad spot with your truck as the 2nd gens had about a .43 Cd whereas my 3rd gen has a .52 and a good bit larger cross-sectional area as well.

You also need to pay attention to your engine tune. I think the 98s were among the trucks that the 360 had the split upper/lower intake manifold with the "belly pan gasket" that was an absolute POS. It would constantly break seal and the intake would suck oil into the rear of the manifold and carbon up cylinders 7/8 and their valves causing a ton of pinging. I had heard where people used SeaFoam in the manifold and hailed it as the miracle ping cure and their ping came back before they ran out their gas tank of 87 and needed 89+ again. Most folks never cured it until they replaced the intake with a Mopar M1 (which is available in a dual-plane and should be good for towing).

I had heard that the stock exhaust manifolds from the 94/95 Magnum engines were better flowing than the later-model manifolds. If you're not going to look for tuned long-tube or tri-y headers you could pick a pair of older junkyard manifolds and maybe help a little.

There's some Dodge Truck forums out there but lately they haven't been very active. You could search some archives and see if there's any tips there. I know if you go to dodgetrucks.org and search for aerodynamics or fuel efficiency you'll get some mega-threads with a wealth of information. There's also the Dodge Ram truck (DiRT) mailing list that I'm on and there's a member there (at DTO also) who incessantly does before/after FE comparison tests and aero tweaks. I want to say he has a truck very similar to yours. You should check that out and scan archives to see what's already been posted.

[klrv6]

Set it closer to the ground and use air bags to keep the rear level when towing. Put the mirror back on, I can't back up our trailer without the passenger side mirror. I also dropped $500 on a set of Michelin X Radials for the suburban. It picked up 3mpgs over the yokohama geolanders I had running on it before. If you do get new tires, make sure to get at least 6ply, 4 sucks on a heavy truck. The best my suburban has hit is 25mpg @ 80mph. Your truck is a chrysler product and I really don't know of many offerings as far as tuning goes.

My neighbor is going through the same thing with his dakota, you get the same mileage as him. I think it's mostly in the computer as to why the dodge trucks have such a hard time getting higher numbers. It doesn't matter what he does to it, it won't get better than 13-14mpg for him. Is yours 2WD?