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I bought this Dakota (1999 Dakota R/T, 5.9L) a little over a year ago. The dealer had performed a fresh oil change on it at the time with 10w30 oil. It had about 129k on it at the time. For the first 6 months I had it, I used it mainly around town - going to Home Depot, hauling the dogs to the vet, etc. From 129k to 133k the truck never used a noticeable amount of oil.

Last December, I had Goodyear rebuild the front end on the truck and since then have been using it as my primary commute vehicle, 35 miles round trip, mostly highway ay 65 mph. Along with the suspension work, Goodyear changed the oil (10w30 again) and also the filters and PCV valve. I've went about 3500 miles since then and have added 2.5 qts of oil.

I want to see if I can address the oil issue. Here are my thoughts:
1) The aftermarket PCV valve Goodyear used might be the issue. I know before they serviced it, there was a Mopar PCV valve in there and it was probably the original. Is an aftermarket PCV valve an issue on the Magnum engines?

2) The dreaded intake plenum issue. I haven't looked down the throttle body yet, but the truck idles smoothly and runs well so if there is an problem here, it can't be a bad leak, I guess.

3) Maybe the change in use is contributing to the oil loss.

Anyone have any thoughts or anythign else I should look at? I don't see any evidence of leaks so it's burning the oil not leaking it.
 

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Aftermarket PCV vacuum draw calibrations can vary. This can affect oil consumption and/or idle quality. Always use an OEM PCV valve.
Oil quality can vary widely as well. Even though it may be a 10W-30, a poor grade of oil can affect consumption and/or engine noise vastly. Just an oil change to a premium recommended brand/grade (meeting or exceeding MS-6395) of motor oil can fix this. Observe the oil odor and pour-speed to compare old and new oils. You may see a big difference. I've seen this with my own vehicles.
A good test of the intake manifold plenum sealing while the engine is idling is to remove the PCV from its grommet and block the breather tube and hold your fingers over the grommet hole and count to 10. Then unblock the hole and note if a pressure or vacuum was developed inside the engine during that time. If the hole draws air after removing your fingers, you have a plenum leak. If air pushes out, you are OK.
 

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I'm not familiar with the 5.9L, but when my 3.0L had the PCV issue, it was spitting oil back into the air filter box. You might want to check that.

If you're not seeing any leaks or any blue smoke, you should find out where that oil's going. Hopefully, your head gasket's okay.
 

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Discussion Starter #4
With the heads and block both being iron, head gaskets aren't usually a problem on the 5.9.

But it did get me thinking: If the heads on a Magnum engine crack, does this cause oil useage issues? I know the factory Magnum heads could have a cracking issue.
 

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The cracking issue is between the valves themselves, and the only thing there is water. Rarely do these cracks leak, but I haven't heard of them cracking all the way up to the valve stems to suck oil. I would tend to agree with the PCV valve first, belly pan second, and pull the oil cap with the engine running to see if there is a developing amount of blowby. I would think you are getting close to an oil change, which going back to the brand prior to the Goodyear repairs may be another solution check, too.
 

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I try to go 6 months or 5k miles on oil changes now. The oil change before I bought the truck was at a WalMart. I didn't pay attention to what brand, if any, was on the decal. I'll have to see what the receipt says Goodyear used.

I'm ordering a Mopar PCV valve as well.
 

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My Spirit uses very little oil driving around town. On the highway it is a different story, I use around a quart every 1000 miles on the freeway. I do not foul plugs or see any smoke so I just top off as needed. Oil is cheaper than tearing into the engine.
 

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"2) The dreaded intake plenum issue. I haven't looked down the throttle body yet, but the truck idles smoothly and runs well so if there is an problem here, it can't be a bad leak, I guess."

Well..my Durango 5.9 idles smothly, doesent smoke and just rarely foul a plug but it sucks
a lot of oil from the intake bellypan.
Its easy to diagnose.
- oil in the plenum, look through the tb.
- vacum in the crankcase with the pcv disconnected, mine sucks like a vacuum cleaner!

I dont use the 10w-30 passcar oil anymore.
- its expensive
- It got used up quickly,(used alot)
- i use atleast 10 gallons of 10w-40 hdeo every year for the rest of my collection.( high quality and dirt cheap 18 wheeler diesel engineoil )
- Consumption became just the half.
- Not the best choice when its freaking cold like below - 25 celsius.
 

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Discussion Starter #9
Another 8 days, maybe 500 miles at the most. Another 1.25 quarts of oil, assuming I filled it completely last time. I also smell oil at times from the truck - not the "burning" oil smell but still an oil smell. It also seems to blow a little smoke at the tail pipe if I rev it up as it returns to idle.
I did Imperial Crowns test at the PCV grommet and there's not a lot of suction at the PCV grommet but there is some. I don't see lots of oil looking down the throttle body but there is some. The PCV valve is oily, both at the grommet and the hose side. I was already leaning toward retiring this truck from daily use because it uses a lot of gas and has a noisy rear axle. This may be the incentive to take it out of daily use and find a more economical vehicle for daily use and fix the truck as time permits.
 

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Noisy rear- have you checked the oil level in there?
 

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It is probably too late for oil. It may need carrier bearings for a growl/rumble above ~15 mph. The pinion bearings turn ~3.5 times faster than the differential carrier bearings and may start to whirr right after starting out from a stop.
Carrier bearing replacement was common.
 

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Yep, I had one of these new and it had to have the rear axle rebuilt at 16k miles. My noise is more of a woo-woo-woo, especially noticeable when turning at lower (parking lot) speeds. There also seems to be some roughness and some chatter. I've got a disc brake equipped 9 1/4 axle I grabbed during Cash for Clunkers, I hope it's in better shape than the one in the truck now.
 

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To top this all off, the AC compressor is rattling on the truck. So the solution is now to retire the truck from daily use and work on these problem areas at my leisure.
 

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Discussion Starter #14
Despite the noisy rear axle, I've been driving the truck some lately.
Got a Mopar PCV valve and the oil use has dropped from over a quart in 500 miles to basically zero.
 

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So it sounds like you had a sticky PCV valve. Good deal and a cheaper and easier fix than pulling the intake manifold.
 
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