Intermittent Oil Consumption

[Phishin]

In my 1990 Chevy K1500 with the old 350 TBI, which I've owned for 18 months and put about 15k miles on, I've had two or three occassions where I experience sharp decline in oil consumption.

Driving around town, I usually burn a quart every 800 miles or so. The engine was a sludged up monster when I bought it, so I am continually running MMO through the crankcase to further clean up the mess.

Right now, I'm currently on a stretch where I almost stop burning oil. It's been 1200 miles since I've topped off the oil (to the top of the hash marks on the dip stick) and in that time, 80% of the hash marks are still covered in oil. That's a HUGE decline in oil consumption.

Usually at the end of an OCI (which I'm about at), I add a quart of MMO, to do some cleaning.

So, here is a theory: I think I have a broken or stuck oil ring on Cylinder #1. The plug will foul in about 1000 miles. Almost all oil consumption is in that cylinder. Could the carbon or sludgy oil "seal up" the broken oil control ring and thus cause decreased consumption? And then when I add MMO, it's cleaning that "scab" off, and my oil consumption returns?

I'd hate to add some MMO now, and have oil consumption return. It's done it to me once or twice before. But I also still got more cleaning to do in that engine. The oil has had a quart of MMO in the crankcase probably about half of the miles I've owned. it.

This all might sound crazy or bizaar, but this is what I've experienced.

 

[Roadkingnc]

If its getting enough oil in the combustion chamber to foul the plug it needs attention.

 

[HerrStig]

Missing any coolant?

 

[Phishin]

Originally Posted By: Roadkingnc
If its getting enough oil in the combustion chamber to foul the plug it needs attention.


Of course. But I'm not throwing a bunch of money at this old engine. It runs fine. Just consumes oil, has some lifter tick and piston slap....it was all sludged up when I got it.

If I tear it apart, the repair process will never end. I'm sure it needs the heads and valvetrain rebuilt, new cam, pistons, rings, rod and crank bearing, etc. I'm not gonna spend money on this motor, when I can get a new GM Crate long block with 3 year warranty shipped to my house for $1600.

I'm just gonna baby her along until she dies. I was just wondering if anyone has experienced this intermittent oil consumption and maybe the "scab" theory of cleaning and re-scabbing.

Originally Posted By: HerrStig
Missing any coolant?


Nope, no coolant loss. No HG problems. Recently replaced the IM gasket too. (like a year ago)

 

[MBS500]

Try piston soak overnight with mmo or kreen. Keep it ocis shot 3000 miles and maybe get overfize oil filters. I wouldn't waste any more money than than. Also check pcv valve and hoses, it might be clogged with sludge.

 

[Phishin]

Originally Posted By: MBS500
Try piston soak overnight with mmo or kreen. Keep it ocis shot 3000 miles and maybe get overfize oil filters. I wouldn't waste any more money than than. Also check pcv valve and hoses, it might be clogged with sludge.


This is part of the reason I bring up the whole "scabbed over broken oil control ring" theory.

I've done many piston soaks with Kreen, MMO, and even Techron. Oil consumption never gets better. Maybe even accelerates right after that.

I've read from a few guys on here that piston soaks should make oil consumption WORSE. Their theory is that the gunk/crud in the ring would help seal up the leak/blow by. I didn't buy it, but I'm beginning to be a believer.

I've tried and tried to improve the oil consumption. It can burn 1 quart of oil on the highway in 250 miles. I can guarantee that almost all of that oil is in cylinder #1. Thought maybe the rings were stuck, so I did all those soaks. No improvement, and like I said, maybe immediatley afterwards, consumption was worse.

Without any cleaners and solvents for awhile, after it's burned a few quarts, consumption really seems to quiet down. Like it has right now. Hmmm.......

And MBS500...the PCV system is perfectly operational. When I got the truck, it was plugged solid. So I rebuild the throttle body and found the plug inside there. It works great now.

 

[heynow]

Originally Posted By: Phishin


I think I have a broken or stuck oil ring on Cylinder #1. The plug will foul in about 1000 miles. Almost all oil consumption is in that cylinder.


How have you determined that almost all your oil consumption is in the number one cylinder?

 

[bullwinkle]

Any blue smoke when engine braking downhill? Or on a cold start?

 

[Kuato]

Originally Posted By: Christopher Hussey
Originally Posted By: Phishin


I think I have a broken or stuck oil ring on Cylinder #1. The plug will foul in about 1000 miles. Almost all oil consumption is in that cylinder.


How have you determined that almost all your oil consumption is in the number one cylinder?


That was my first thought also.

My next thought is that it is certainly possible that the cleaning has removed crusted oil(for lack of a better term) from the area of the leak, allowing that seal/ring/whatever to do its job the way it was designed to do.

 

[ARCOgraphite]

MMO is likely exacebating the problem at this point. Thats low miles but there have been issues with "net build" instead of "matched" rings and pistons ON gm V8. I usually see consumption through the valve guides and the PCV. My last chevy W/T didnt have a one-way piddle valve on the pcv, only an open oriface and that engine (4.3l) drank oil. Maybe try the universal remedy of 10w30 Rotella Triple protection dual-rated fleet oil and 3-5K oci depending on use. Also add an oil mist separator/collector jar to the PCV line.

 

[Phishin]

Originally Posted By: ARCOgraphite
MMO is likely exacebating the problem at this point. Thats low miles but there have been issues with "net build" instead of "matched" rings and pistons ON gm V8. I usually see consumption through the valve guides and the PCV. My last chevy W/T didnt have a one-way piddle valve on the pcv, only an open oriface and that engine (4.3l) drank oil. Maybe try the universal remedy of 10w30 Rotella Triple protection dual-rated fleet oil and 3-5K oci depending on use. Also add an oil mist separator/collector jar to the PCV line.


What do you mean by "net build" vs. "matched" rings and pistons? I'm pretty sure this engine has never been opened up.

My PCV does have a one-way piddle valve (typical PCV valve), and it's operational. There is a lot of vacuum on that hose going into the base of the TBI. I guess a catch-can couldn't hurt, but it wouldn't solve any "consumption" issues, but it would end up in the can and not going through the intake.

I think my valve seals are pretty decent. But my guide on that cylinder #1 may be worn. I don't think a bad valve seal could cause a quart to get burned up in 250 miles at 70mph. I think it would have to be something more severe. That's why I always thought it was a broken ring or worn valve guide.

Originally Posted By: Christopher Hussey

How have you determined that almost all your oil consumption is in the number one cylinder?


After 12k miles, the plugs in the other 7 cylinders looked perfect. No oily residue, no soot, no caking. #1 was caked over. And if I don't keep Gumout Regane in the gas tank, I'm replacing that plug every 400-600 miles because it's fouled by then. Perhaps 50% of the oil consumption is in cylinders 2-8, but it's quite obvious that #1 is the main contributor.

Originally Posted By: bullwinkle
Any blue smoke when engine braking downhill? Or on a cold start?


I see a puff of blue smoke every morning. Smelly/oily exhaust. I'm pretty sure I have a partially collapsed lifter or leaky lifter. The engine will develop a lifter tick after it's warmed up. When I rev it up a bit for 10-15 seconds and build oil pressure, the tick disappears for a few minutes at idle, and then comes back. Never ticks at start-up when it's cold because oil is thick and therefore higher oil pressure (my assumption). If I shut the truck off when it's fully warmed up, it won't tick if I re-start fairly soon, but after a half hour or so, she will tick at start-up (leaking lifter....my assumption). But give it a little increase in RPM's for a few seconds and let it return to idle, and the tick is gone for a minute or two, and then slowly begin to reappear.

 

[71Chevyguy]

I have some experience with worn out engines since I owned two cars that had some pretty bad oil consumption. Are these the correct ways to fix it? Of course not but you already know that and mentioned that you simply do not want to sink the money in it. I felt the same way and had success using these methods. Feel free to try any of it and see if it helps you at all. I had a 79 camaro 305 that burned so much oil that it was capable of burning 5 quarts in one day of normal driving. Probably as bad as it gets before it dies due to running out of oil. I put MSD ignition on it to give it more spark which did a very good job of keeping the plugs clean. I had to clean them daily if I wanted to drive the car since they were soaked in oil.
As for oil give Rotella a try. I used Rotella T6 5w40 and it actually stopped consumption in another car that I had that was also very sludged up. Does not hurt to give it a shot. Not saying this is "the best oil" but it worked well for me in vehicles I had with consumption and also did a very nice job cleaning things up. Rotella T5 10w30 may also be a good choice but I think the 40 weight may be part of the reason it may slow down or stop consumption.
Another product I used was called Restore. It is the stuff in the tall silver can. Pretty sure that is what it is called. Shake well before adding it to your fresh oil at an oil change. Again another product that is a last ditch effort to patch up a problem but in my Camaro it actually stopped my oil consumption completely. Not bad for a vehicle that was burning 5 quarts a day. You may want to try a small can if you want to try it. Do not want it to hurt anything else in high amounts since you feel only one cylinder is affected. It did work very well for me. I used it every other oil change and it kept consumption down. Not too expensive and worth a try.
For oil in that Camaro I used 4 qts of 20w50 and 2 bottles of STP but my engine was in way worse condition than yours so I feel for you that would be a bit extreme. High mileage oil can be a good choice for you as well.
Good luck and keep us posted to what you have tried and if it worked for you. I think many of us would be interested to see what happens.

 

[Kruse]

What filter are you using? The reason I ask is that a buddy of mine picked up a Chevy pickup from a used car lot awhile back that is similar to yours. He changed his oil and filter when he bought it at a local mom-and-pop service station and did it again 3K miles later with a NAPA ProSelect. The service station has a habit of taking a hammer with a sharp point and punching a small hole in the filter so it drain better. (It's their habit, not mine) Anyway, with the base plate facing down, this filter oozed out about a half of cup of a sludge from the top of the filter. The next filter did the same thing. Obviously, the sludge was getting cleaned and was filling up the filters beyond capacity.
I'd use a very good filter on this truck, not the cheapest one on the shelf.

 

[71Chevyguy]

Oh and one more thing you can try that I have seen work on several worn out engines burning oil. You can replace the spark plug in your bad cylinder with an Aldor spark plug. It seems they are still around. They are supposed to fire in oil and I had much success with them even before I added the MSD ignition. Did not foul as much for me so for you it may just stay clean. All you would need is one for the bad cylinder. J.C. Whitney used to carry them but I am sure with some research you can still find them out there somewhere. Once again best of luck.

 

[PandaBear]

Have you also check your valve stem seal? A puff in the morning can also be an indication that the valve stem seal is bad. You can probably do a leak down test to see.

 

[Phishin]

Originally Posted By: PandaBear
Have you also check your valve stem seal? A puff in the morning can also be an indication that the valve stem seal is bad. You can probably do a leak down test to see.


Leak down test in Cylinder #1 showed quite a bit of...well, leaking. Out of spec for sure. Plus, it showed about 105psi for compression. The other 7 cylinders were around 140-150.

Yeah, the engine only has 165k miles on it. But for 22 years, and 150k miles, I have no idea how bad the previous 2 owners abused this truck.

I occasionally have a some pinging under low RPM's and load when accelerating (like when it first shifts into OD, which is around 35-40mph). So, I like keeping PEA in the fuel to try to dissolve some of that carbon that I know is built up on that oil burning #1 cylinder. 93 octane prevents this as well. This summer, I slowly poured about a gallon of water down the intake to try to decarbonize her. Yeah, it worked. Holy Cow. But my lord, the oil consumption rate was never higher after that. That is another reason I think the carbon/gunk is scabbing over wherever the oil is blowing by (rings or valve guides).

I might try the restore, might not. Maybe I'll try that Alder plug. But right now, keeping PEA in the fuel tank is preventing any fouled plugs. And right now, she ain't really burning any oil!!!

Perhaps a majority of my problem is MMO thinning the oil too much. Next oil change, which is soon, I'll try the Rotella T6 and not add ANY MMO or Kreen. I always use a Purolator classic filter. I usually cut the filters open, and they just have hard-crusties in the pleats, but they aren't even close to being full.

The truck runs surprisingly well, as long as I stay on top of it, and I do. I used it 6-8 weekends this year to pull my heavy 20' fiberglass boat 3.5 hours one way up to Lake St. Claire and back. Never a problem. Just burned oil like crazy. LOL!!

I'm gonna MAKE MYSELF keep the MMO and other solvents out of the oil for awhile and see what the oil consumption does....for now, and after the oil change.

 

[antiqueshell]

Originally Posted By: Phishin

I'm gonna MAKE MYSELF keep the MMO and other solvents out of the oil for awhile and see what the oil consumption does....for now, and after the oil change.



STOP USING THAT SNAKE OIL!

It obviously hasn't helped anything up till this point. If anything it has made things worse. Like many snake oils do.

 

[bullwinkle]

Never did hear which oil you were running? MaxLife (in the slightly thicker than recommended 10W30) actually cut my oil consumption by 1/2 in my '94 350 TBI Suburban-from a quart every 750 down to 1 every 1500 miles. Granted, I didn't have as big of a oil burning problem as you did-there may be nothing that will stop it. Wonder if those old no-foul sparkplug extenders are still available.

 

[Phishin]

In my signature, I state that I use Valvoline 10w40 conventional in the truck. This past oil change, in order to continue to try to find the right viscosity and perhaps decrease oil consumption, I added my usual quart of Valvoline 20w50 conventional when it was a quart low, and then a quart of MMO.

The last two quarts that went in it after the MMO was 1 quart of Valvoline 20w50 conventional and 1 quart 50/50 mix of straight 50 weight (Valvoline VR1) and Valvoline 20w50 conventional. This should have really thicked up the oil. And my consumption has really slowed down.

I think I'm onto something....LOL!! No more MMO if I want to reduce consumption and perhaps try 3 quarts of 10w40 and 2 quart of 20w50 at my next OCI.

BTW....what would the resulting viscosity be if a 50/50 mix of 0w40 and straight 40 weight be? Just wondering.

 

[gregoron]

One way short of fixing the problem is deactivating that cylinder and its counter cylinder(s).

http://ecomodder.com/forum/showthread.php/cylinder-shutoff-2200.html