So I have had the D for a total of 4K miles now. Two days ago I decided to check the oil since I have ran it 3K and just got back from a trip. Was a bit low. So I went to add oil but all I had was 10w-40 full syn. I had 10w-30 in. So I said well it isn't much of a difference I should be good...was good for the first couple miles then all of a sudden after accelerating from a light it just bogged down!
Has been doing it ever since...any ideas?
I know I need to change the oil, and I want to do a tune up(plugs, wires, cap/rotor, etc.) But is there anything I should look for?
The oil gauge is always above 40 now, it would sit at about 30 at a light. Now it sits at 40...

 

Also! Before I forget again...
I have crazy brake fade, I notice it more and more. But as I am braking the slower I go the more the pedal goes down. Weird thing is I have to push the pedal down more then half to even engage the brakes. I checked my pads and they are at 85% front and rear. Drums are clean and disks only have 4K miles on them. Fluid was replaced 4K ago and is clear and not to full.
I was thinking mabey I have bad lines?

 

Not sure on the oil but I am interested in the brake fade, I have somewhat of the same problem.

 

I was thinking I would just swap all the lines for stainless steel...but I want to make sure it is the lines first. Haven't had a chance to crawl under and check every inch.
Are there any differnces in brake lines between 98 and 00? I found a set of stainless for 2000 and up.

 

Change the oil to all 10w-30 when you get a chance, the increase in oil pressure is caused by the heavier oil.

Now iirc these have vacuum boost brakes. A vacuum leak somewhere could account for the rpms and poor brake performance.

 

As well as a bad check valve on the brake booster. It is the nipple that the large vacuum hose attaches to on the brake booster. Your issue sounds more like a brake issue then and engine issue.....IMHO

Dealer for the check valve.

Not much difference on the 40 and 30 weight, but I would pull it out at your next oil change. With that much dilution I can't think it would be much worse then what is in there already.

 

Got it, I will have to check the check valve. I didn't even think of a vac line either...great gonna be a chore going and looking at everything brake wise.
I am gonna change the oil here in the next couple of days. I need to do a tune up still.

 

If the truck is sitting still with the engine running and you're applying pressure to the brake pedal does it gradually go down to the floor? If it does then you have a bad master cylinder otherwise I'd think you still have some air in the brake lines that need to be bled out.

 

I did that test bwdakrt, thankfully it doesn't go down. I stays but I am mabey 75% of the way down in order to stay put...It's weird cause I took it to les swab cause i couldn't get the rear's off and I was being lazy!...and they said they couldn't tell me what was wrong but that there was something wrong...lol nice!

 

When you do the tune up, go to your local parts store and get Champion Copper plugs, yes the cheap ones, the number is under the hood on a label and install them, remember to gap them to .040 before install.

While your there get a distributor cap and rotor with brass contacts. Go to your dealer and get a set of OEM wires, or Mopar Performance wire, or MSD 8.5mm Red wires and install.

Now you will have the correct parts to make your Durango shine.