oil burning

[A.bandini]

Hi all, new to the site, but have been a lurker here and there.

 

I have a 85 720 that has been burning significant oil lately, I'd reckon about a quart every 2 weeks, from around town occasional driving. 

 

I've had the truck just about two years, its got 220,000 on the odometer and has noticeable timing chain slap, so I imagine the engine isn't in top tier shape, but I'm hoping to keep the truck going as a beater. When I got it, I put in new plugs, coils, distributor, ect, but haven't really touched the engine, apart from oil changes and pouring some lucus in with it. 

 

Most recently I've been using Shell Rotella T4, 10w30 as I'd seen recommended here, thinking that thicker oil may slow down the burning, but  I had the oil light come on last night, and had to pour another quart in.. 2 weeks after topping off. 

 

I know it's a big question with not much to go on, but any theories on what could be causing that amount of oil burn?

If its a major problem (piston rings or whatever), do you reckon I could keep the truck doing by feeding it oil as needed?

Don't know if it makes sense to pay for major engine work on a beater. 

 

Thanks for any input. 

[datzenmike]

First and easiest thing is to put a large sheet of cardboard under the engine and check it in the morning. Did any oil drip off the engine? Driving it would drip more so do you think this enough to add up to a qt. every 2 weeks? Are the sides and rear of the engine wet with leaked oil? Inspect the oil pan, is it wet?

 

Perform a compression test on a warm engine. If below 130 then the engine is getting well worn. Pressures should be within 15% and lower is better. Record the number then add a few tablespoonfuls of engine oil and perform the compression test again and record the numbers. If there is a significant rise in compression numbers then the rings are worn out and so are the oil control rings.

 

If the engine is severely burning oil you could also do a leak down test but it won't tell you anything different than a compression test which is a lot easier. A leak down test will pinpoint rings, intake or exhaust valves or head gasket as the cause of loss of compression but only the rings are then most significant source of oil burning. If severe oil burning AND the compressions are also low but improved with oil added to the cylinder then it can be assumed it's the rings.

 

The only other source of oil getting into the combustion chamber is very bad valve seals. They would have to all be in very bad shape to need a Qt every two weeks.  

[A.bandini]

Thanks for the reply. I had assumed it would be a leak, but left some cardboard under the engine a few weeks ago as you suggested and it stayed dry.

 

I think you're right that a compression test is the next move. Will work on doing that next.

 

Thanks! 

[banzai510(hainz)]

put 20-50 in it but I say its a oil burner cause if you waited till the oil light came ON to ck the oil, its pretty much spent then I say.

 

does it has a STINK out the back???

Edited December 7, 2022 by banzai510(hainz)

[datzenmike]

If it smokes most under load, then rings. If puff when you start up, valve guide seals.  

[A.bandini]

Thanks for the input, I'll buy the 20-50 next time and see if there's a difference with that.

 

Haven't noticed it smoking either at start or under load, but the exhaust is a whole nother story. That said, doesn't stink either like I would expect if it was burning through a lot of oil. I'm gonna keep an eye on it in the next few weeks and see what I notice.

 

No chance that the worn timing chain plays a part in it, right? Like I mentioned initially, it slaps around a good bit when I'm driving. 

 

 

[datzenmike]

Unless the timing chain is selling used engine oil... where is it going???? 

 

 Cardboard under it overnight shows no leaks.

 

11 minutes ago, A.bandini said:

Thanks for the input, I'll buy the 20-50 next time and see if there's a difference with that.

 

Once oils are up to temperature they are close to the same viscosity.  The 20w50 rating is their cold startup viscosity.

 

 

11 minutes ago, A.bandini said:

 

Haven't noticed it smoking either at start or under load, but the exhaust is a whole nother story. 

 

Well what's the story? Has to be going somewhere. Not dripping, not noticeably smoking. Is the tail pipe black and oily/sooty

 

11 minutes ago, A.bandini said:

 

No chance that the worn timing chain plays a part in it, right? Like I mentioned initially, it slaps around a good bit when I'm driving. 

 

 

 

Not unless the timing chain is selling used engine oil.

[banzai510(hainz)]

the 20/50 is a Hail Mary

I was running straight 40 or 50wt at the end on one motor and didnt burn any less, AKey was I ran it out of oil and was a oil burner after that.

 

hope it has a PVC valve  otherwise it sound like soemthing is sucking it up if not leaks.

 

whats does the spark plugs looks like?

Edited December 9, 2022 by banzai510(hainz)

[datzenmike]

A qt. every 2 weeks should be smoking and or dripping. 

 

Had a Ford van that gained oil!!!!!!

 

Turned out it was sucking ATF from the transmission through the vacuum modulator.

[Thomas Perkins]

What does your spark plugs look like.The reason I had a Jasper re manufactured engine installed in my 720 was cause of the piston rings.I could not make it to work without my spark plugs getting massive oil on them.I kept 2 sets to make it thru the week,then I got the new engine back in 2009.After a week of this,I got Jack,the Jasper installer to install the engine,got around 100,000 miles on it in 13 years.Still runs like new.I paid 3200.00 total for it.The engine itself was 1900.It came with a 3 year or 100,000 mile warranty,which ever came first.

Edited December 9, 2022 by Thomas Perkins

[A.bandini]

23 hours ago, Thomas Perkins said:

I could not make it to work without my spark plugs getting massive oil on them.I kept 2 sets to make it thru the week

Wow, the plugs would get fouled that frequently?

 

I just pulled a few plugs to give a look, I last replaced them about 18 months ago, don't believe i am able to upload any photos until I get a few more posts, but they look more carbon fouled than oil fouled to my eye. I'll look forward to y'alls input though. 

 

Quote

On 12/9/2022 at 3:25 PM, datzenmike said:

Well what's the story? Has to be going somewhere. Not dripping, not noticeably smoking. Is the tail pipe black and oily/sooty

The short story with the exhaust is that it's rusted to hell. It needs replaced, but of course no sense in doing that till I can make a determination about the engine health. Will try and get that compression test in the next week or two, and will go from there. Didn't know that about oil ratings equalling out once it gets up to temp. My asking about the timing chain being the culprit was pure wishful thinking. 

Thanks's everyone for the input. 

[datzenmike]

Whats your guess at your gas mileage???

[powderfinger]

If you are burning 1 quart every two weeks with just occasional around town driving then there should be signs of the oil burning. Is there any excess soot on your truck near where the exhaust exits. I had a 92 Honda Civic I was driving 60 miles per day and near the end it was burning 1.5 quarts a week which is probably close about what yours is burning since you said it was just occasional around town driving. 

 

My friend followed me home one day and when we were driving up the fairly steep hill to get to my road and I was giving extra throttle in an attempt to maintain speed he said he was seeing oil droplets on his windshield from my exhaust! lol The back of my car where the exhaust exits was always black from the oil burning. What is surprising is the car didn't smoke as bad as I would have expected for the amount of oil it was burning. Not sure you could even notice it at idle. It was mostly when I would accelerate.

 

Makes me wonder how much oil some vehicles I see on the road are burning because I have seen some that were smoking really bad.

Edited December 21, 2022 by powderfinger

[datzenmike]

Here last 8 days ago.

 

From the testimony given this doesn't add up easily. Oil doesn't just disappear. That much oil loss would:

1/ burn: smoke excessively, foul plugs, oily black tail pipe.

2/ leak: drip oil or leave oil all over the undersides of the car.

 

 

[Stoffregen Motorsports]

Burning oil can be caused by worn rings, stuck rings or broken rings. It can also be caused by worn valve guides and/or hard broken valve stem seals. But if it's burning a qt every two weeks, it's more likely the rings.

 

There is an ancient chinese secret method for freeing up stuck rings. A trick I have used before with success - add a quart of ATF to the engine oil. The high detergent properties of ATF allows it to get in behind stuck rings and loosen them up. It will also clean up any sludge in the block or cylinder head. Basically, you leave it in the engine for about 500 miles and then change the oil and the filter.

 

There is one drawback to this method, it can loosen large chunks of gunk which may get sucked into the oil pickup and block the screen. This has never happened to me, but I have been advised that it may happen.

 

This trick is basically free and can help, but use at your own risk.

[datzenmike]

I've done this about a week before an oil change to 'clean' an engine out. This was a very dirty engine to begin with. Definitely replace the filter. You can also run a diesel oil which is very high in detergent to suspend the carbon deposits that diesels produce. It will clean an old engine and then just keep it clean after. If you keep engine in tune and change your oil and filter in a timely manner you should not have crap build up. Dirty engines are usually from a previous owner.

[bottomwatcher]

At this stage the damage has been done and at those miles and being a beater my Dad said "oils cheap". I have run all kinds of beaters that seem to keep going as long as you don't run em out of oil. I am cheap but not lazy. Only takes a minute to check the oil. Low? Add some and keep on rolling.