Okay everybody hows it going? I have a 1998 dodge ram 1500 slt laramiewith the 360 magnum in it. The truck is awesome and that 360 will haul but my question is concerning the spark plugs/wires. I just bought a set of bosch platinum 4 plugs and autolite professional series wires. Im also running a drop in k&n air filter. How much hp do you think i will gain if any off just running those platinum plugs and good wires. I will be getting dual exhausts put on it in july when i have enough money, seing that im only 16. My other problem is that my cat is going bad, im afraid its robbing me of hp and gas mileage. I calculated my gas mileage and im getting 11 to the gallon running on interstate every day. Surely something isnt right, but this tune up should help seeing that their is 120,000 miles on the truck and the plugs or wires have never been changed. Okay, do does anybody have any input on my spark plugs/wires, and a suggestion to what to do about my cat.

Thanks

 

I would replace the cat ASAP! A bad cat can really hurt your mpg, and seeing as the plugs and wires have never been changed, they can't hurt your HP or MPG.
Good truck by the way, I have the same. Another way to improve MPG is to keep your foot out of it. but thats just not fun.

 

The plugs and wires: Platinum +4 are junk in Magnum motors ... and (unless you have an actual problem with one) changing wires will not gain you anything. Wire just don't wear out like people think they do. If you have a pinging problem caused by crossfiring between the wires, a thicker set CAN solve that. Campion truck plugs (one range cooler than stock) at .040 or Autolite (same deal).

How fast are you pushing it on the highway? You're trying to shove a brick through the air ... the faster you go, the more drag you have to overcome. 11 mpg is not out of normal range for a 5.9L. I get 11.5-12.5 no matter where I am ... highway or around town ... babying it or tearing it up ... no difference.

How do you know that your cat is going bad?

 

i got the 5.9 in my 97 and i am down in florida with it now and averaged 16.5 on the highway

 

Definitely towards the upper end of the MPG scale for a 5.9. Your mods help, I'm sure.

 

i think so too

 

I`m running the Bosch Platinum + 4s in my 5.2, and not only do they run great, but I also saw an improvement in mpg.

 

Some light reading:

https://dodgeforum.com/m_208634/tm.htm

https://dodgeforum.com/m_366844/tm.htm

https://dodgeforum.com/m_425905/tm.htm

 

1999 5.9 Magnum 4x4 Quad, went from 13 to 14.2 m/gl with NGK plugs, MSD coil and8.5mm MSD Superconductor wires.

 

Today I pulled out the bosch that were in the truck when I got it. Onone the ceramic was cracked and on 2 of them the electrode was ate away pretty bad, but the truck ran fine with them. I switched to champion truck plugs.....I dont really notice a difference while driving around town so far.