Sudden loss of oil

[Brian VT]

1987 6.9 n/a. I've always (for the 3 years I've had it) had to add a quart every tank or so. No biggie as I don't drive much and usually not far from home. And this is the oilburners forum, right?
Saturday I had to go to the dump. I checked the oil. The dipstick was bone dry. I've seen it at the low mark but never below that. So I added 2 quarts. It poured like molasses in the 9 deg. temperature. I started it and it sounded fine and I let it warm up for almost 20 minutes and then drove to the dump. I got home and let it sit for 20 minutes and then checked the oil again. Just the tip of the dipstick showed oil. What the heck?
The truck ran fine and didn't sound any different than always. Oil pressure is @ 20 at idle and @ 40 at speed. Same as always. There's no more smoke than always. There's no oil on the ground where I park it.
Could the dipstick somehow be lying to me? Or where is the oil?

 

[WrenchWhore]

"Don't drive much and usually not far from home"...Sounds like it needs to be worked. Also, if you're running conventional oil it'll burn that off faster than say a synthetic blend/synthetic. I saw rapid oil consumption just from changing engine oils. CDR could also be suspect. IMO these are not short drive engines since they take some time to warm up especially when it's cold. Babied driving/low load/extended idling is a recipe for glazed cylinders. These trucks want to work so you gotta give her what she wants.

 

[Brian VT]

I haven't done anything different than I have for the past 3 years. Delvac 1300 Super 15w-40 synth. blend.
It's never been more than a quart low and I check it at every fill up. The dipstick was dry and adding 2 quarts barely got it to show on the dipstick (after driving 15 miles with the added oil).
I would expect oil usage to gradually increase over time but this is so drastic of a change during the time of just one tank full.

I'm nervous to add more because the engine sounds fine (not tapping or rattling) and I've heard that over-filling is worse than being low. Is there any way that my dipstick could be lying to me somehow?

 

[WrenchWhore]

I don't see how your dipstick could lie unless the dipstick is loose on the clamp or you're checking the engine when it's cold verse hot. You'll obviously get different measurements for both. If you aren't seeing excess smoke, no leaks, and no issues i'd go run it hard. Make sure that pedel hits the floor. Take oil with you and top off as necessary if it gets too low. Just my .02

 

[Brian VT]

How do you mean "run it hard"? High load or high RPMs?
I have some big hills here that I could make a bunch of runs up. Or I could drive around in 2nd gear of my C6 auto. for a while (I'm not near a highway where I can get above 60 mph).

 

[WrenchWhore]

My personally favorite is hitting a steep grade carrying or towing a heavy load. RPM's somewhere around 2500 at max power and keep it at a steady speed under WOT. BUT this is not always possible depending where you live. High load and higher rpm are good IMO. My main objective is to keep it there under load as long as I reasonably can to generate heat.

This is a good video to kinda explain what can happen. They talk about glazing right around 12:30

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[Nero]

I second the theory you need to work it a little harder. Rings could be coking up. Work em hard to clean em up.

 

[Brian VT]

Maybe I wasn't a good candidate for buying this diesel. I only bought it because I wanted old and simple. The only "work" it gets is putting my boat in the water in the spring and hauling it out in the fall. Other than that it's mostly used for weekly dump runs, Home Depot runs, and trips to the corner beer store. 60 mph tops and only for very short stretches.
I wanted something simple that I could maintain at home. I have replaced the injectors and the return caps and lines and the IP and timed it. And some other electrical repairs. It has mostly been reliable since then. I'm not opposed to getting my hands dirty and spending some money. But this oil loss has me flustered and nervous.
Is there a chemical additive that could help me with this coking? And could you explain what causes coking and how it affects the engine? And maybe where my oil might be going all of a sudden?

 

[Nero]

Cokeing is when the oil gets baked onto engine parts. Diesels that get low load or high idle time can have this happen to them. The piston rings get stuck in the piston, and the second ring for oil scraping.. Does nothing.

 

[Brian VT]

So...should I sell it and buy a gasser or can I use an additive to counteract my usage habits to prevent cokeing?

 

[Nero]

Using a good quality oil and driving er harder will help prevent coking.

To get existing coking to clean up, use some sort of oil addative. On gassers I use seafoam in the oil. Diesels, stiction cleaner like Hotshot Secret is something people use for powerstrokes, I'd imagine it would work well for piston rings too.

 

[Brian VT]

Ok. Thanks.
Is Delvac 1300 Super 15w-40 synth. blend poor quality?

 

[IDIBRONCO]

If you want to work your engine, hook onto your boat and run your truck hard. That should work since I think you've said that you have a bigger boat.

 

[Brian VT]

My boat is tented in the back yard for the winter. And I have nothing else heavy to haul.

 

[ROCK HARVEY]

I don’t think they make it in 15w40 yet, but Valvoline makes a new oil called “restore and protect” that is making waves among oil nerds for its ability to clean sludge and deposits. They do make a 10w30 though which would work in the wintertime. If you’re already adding oil maybe something like this would be worth trying.