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1996 F250 - burning oil

D

dhermesc

Well-known Member
My son's 1996 F250 has the 351W (5.8) and about 140K miles. It runs great - good power, no smoke, starts easy but it is burning a huge amount of oil. About 1 quart for every 100-200 miles. If you only checked the oil when you filled it up it would be almost 2 quarts low. Could the oil ring be letting this much oil by while the compression rings are still doing their job?

When we bought this truck the thermostat was sticking and had probably gotten the engine very hot with the previous owner. We flushed the system and installed a new thermostat and everything is fine now. A mechanic told us that getting an engine hot could cause the cylinder walls to glaze and contribute to oil burning - at the time we didn't know it was burning this much oil. Currently running 5W40 Rotella T6.
 
Are you sure that it is not leaking? I would first check underneath for any signs of leakage. If it is reasonably dry underneath, I would look at doing some serious testing.
Using that amount of oil, there should be some indication of smoking if it is burning it. Besides oil rings, valve guides are a possible cause of oil consumption. Or, more likely, valve guide seals. Overheating will make the seals get brittle and split. This would be a more likely cause than oil rings.
It takes a LOT of heat to cause oil rings to lose their tension. Also takes a lot of heat to glaze the cylinder walls to that extent.
 
I had always heard, so only the messenger, that getting hot takes the temper out of the rings. With that being said, 140K on those old engines is very good, I would bet the oil rings, valve seals and guides are just shot.

It is probably time for a reman or replacement truck.
 
Your t6 is full synthetic oil. Try going to T4 non synthetic. Had an 06 chevy impala that bought used and less than 20,000 miles on it . When it came due for first oil change local GM dealer said synthetic oil. Well it used a quart every 1,000 miles and after 3 oil changes I went back to conventional oil and it doesn't use a drop between oil changes.
 
Three places for oil to go:eek:n the ground from a leak,out the exhaust,or into the cooling system from a bad oil cooler.and it would take no time at all for the radiator cap to start "venting " it that way.
 
Would recommend changing back to the factory recommended motorcraft motor oil of the appropriate weight. Also would look really close at whether or not it has any oil leaks. These were bad about oil leaks after the gaskets get old and get enough miles on them. Also it might only be leaking while engine is running. A couple things I would look into before digging into it very far.
 
That is a LOT of oil for sure. First thing I would do is switch to 10-40 dino oil and see what happens. Synthetics wont smoke as bad as dino oils and if it still has the cat on it the heat generated burns off a lot of the smoke too. Getting extremely hot will indeed cause an engine to burn oil but it is from rings loosing tension and the valve seals being ruined not cylinder glaze.
 
I had a Ford F250 Ranger XLT in the late 70s. It had the 400 engine. Would use a quart of oil every 100 miles. Had it to numerous shops and no one could figure it out.. good luck
 
In mid 70's I bought a new F150 with the 351M and did first oil change at 1,500 miles and used Kendall oil which it used oil running it. Went to dealer since it was under warranty and they said change brand of oil so I went to Shell and it stopped using on the very first oil change.
 
I am very dubious about your "no smoke" claim. Either it's NOT "burning" oil or it IS smoking.

Leaking a quart every couple hundred miles would definitely be visible anywhere the truck is parked, so I tend to believe the oil is going out the exhaust. Worn valve guides are a common problem for small-block Fords, and that would be the first thing to check. At highway speed, take your foot off the gas for a few seconds, then floor the accelerator as you look in your mirror. If the intake valve guides are worn, you'll see a cloud of blue smoke behind you.

Intake valve guides are simple enough to repair. If there's no automotive machine shop nearby, just exchange the heads for rebuilt ones. Of course, you should do a compression check first; if the engine has been repeatedly overheated the cylinders are likely scored.
 
I am thinking more about this, and reading others posts.

It HAS to smoke if it is burning that much oil, thinking more about a leak.
 
Rings have lost their tension. You could cut consumption considerably by switching to 30 or 40 wt oil but it's going to need rings to stop.
 
When you change the oil, are you filling it to the dip stick level or by the recommended refill? Could have the wrong dip stick if it takes more than called for.

That much oil is going to be obvious where it's going. I've had old junkers that poured out the rear main every time it was parked, and they did not use excess oil. A leak of that size would be dripping off the rear bumper!

Might do a plug check, see if they are showing signs of oil deposits, sticky black on the end of the threaded part, black spots on the insulator, or crusty carbon deposits.

Do check the PCV valve, go ahead and replace it. Check the vacuum to the valve, could be the line is clogged or collapsed. Check the breather to the air filter, it needs to be free flowing too.

Have a look under the valve covers, the drain back holes could be sludged to the point they are filling with oil and sucking down the PVC. That is a severe case of neglect and worn rings to make that kind of sludge. Could be a result of the past overheating. If it is sludged that bad, cleaning it out might help, but eventually it will need a rebuild.
 
Carpenter, my thoughts exactly, a plugged crankcase vent will shove oil out all over the place and put it out the exhaust too.
 
(quoted from post at 08:56:52 11/12/18) I am thinking more about this, and reading others posts.

It HAS to smoke if it is burning that much oil, thinking more about a leak.
Click to expand...

Catalytic converter MIGHT be burning the smoke.
 
(quoted from post at 15:14:02 11/12/18) My son's 1996 F250 has the 351W (5.8) and about 140K miles. It runs great - good power, no smoke, starts easy but it is burning a huge amount of oil. About 1 quart for every 100-200 miles. If you only checked the oil when you filled it up it would be almost 2 quarts low. Could the oil ring be letting this much oil by while the compression rings are still doing their job?

When we bought this truck the thermostat was sticking and had probably gotten the engine very hot with the previous owner. We flushed the system and installed a new thermostat and everything is fine now. A mechanic told us that getting an engine hot could cause the cylinder walls to glaze and contribute to oil burning - at the time we didn't know it was burning this much oil. Currently running 5W40 Rotella T6.
Click to expand...

Do you have a leak down tester? I think you need to check the health of the engine.
 
I bought a 90 GMC with 140,000 on it, immaculate inside and out, Texas truck. Started using lots of oil right after I bought it like 3 qts. in 1000 miles. I decided valve seals would be the easiest thing to try, turned out they had just been replaced and done wrong. The perfect circle type on the head were all split probably from not using the proper driver and the orings on top were put on before the springs were compressed and weren't sealing anything. Truck never used any oil since and I sold it 4 years ago with 286,000 on it. I've also seen engines suck oil through old, hard, deformed intake gaskets.
 
I used to think that too until my son in law and brother in law both had Chevy equinox's that did it with absolutely no smoke and no leaks. I'm sure they laid a hurting on the cats but they burned it all. GM said ring tension & replaced the Pistons & rings only under warranty. Made it 50,000 more miles and started again. Got traded then.
 
If it's been that hot expect some serious piston damage too. When they get that hot they detonate and melt the tops of the pistons. There is no snake oil remedy that will fix your problem. Yank it out and rebuild it.
 
Those motors were likely factory spec'd to run 10-30 oil. Not what you're running in it now.

If it isn't smoking...……..valve cover gaskets, oil pan gasket, rear crankshaft seal, or front seal. If it were actually burning that much oil, you'd be throwing codes. Most likely mess up the O2 sensor.

My 1994 F-150, 300cid is sitting at 265,000 miles, and still runs fine. Only thing is a leak from the side gasket which covers the pushrods. Pretty common on the 300's.

1994 F-350, 460cid is sitting at about 160,000 miles, and runs fine except for the IAC solenoid/actuator. Needs replacing.....idle becoming uncontrollable.

IMHO, the family of engines in Ford during the mid 90's were the best of both worlds. Proven engine design, decades of in-service time to iron out all the bugs. And, they were finally married to computer engine controls.

Emission requirements, and cost cutting, after these years, resulted in just about a new engine style every model year. No time to really find out if they were good designs, and the consumer got stuck with them. Seems all the light truck manufacturers feel that smaller is better. The new trucks strain to do any real work. I just don't believe all the small blocks are gonna last for the long run.
 
The Idle on my 460 jumps up and down with air on but the AC is low and cycling with compressor kicking in and out. The AC
on mine runs anytime you use defroster.
 
No smoke on this one either - no cat either. If it had one I suspect it would have been clogged by down
 
No leaks on this engine. Its actually pretty clean given the year and miles. I know a lot of 302s/351s with the leaking rear main - extremely common those engines but this one doesn't have an issue.
 
It was running 10W30 and we switched to 5W40 when it became apparent it was burning so much oil. Switching from 30W to 40W did nothing for oil consumption.
 
(quoted from post at 20:34:24 11/12/18) It was running 10W30 and we switched to 5W40 when it became apparent it was burning so much oil. Switching from 30W to 40W did nothing for oil consumption.
Click to expand...
If you wanted to increase viscosity you would increase the first number. IE: going from 10w40 to 15w40.

Going from 10w30 to 5w40 would decrease viscosity.
 
It takes 6 quarts to fill when you change the oil and filter. The dip stick is measuring correctly. It is not leaking any oil - its actually pretty clean and dry for the year and miles. It is not smoking - although I suspect that is burning the oil through the rings. It seems like when it comes through the valves the blue smoke on acceleration is usually very visible - and it doesn't take much to make it smoke. My old Grand Marquis with a 4.6 needed new valve seals (common issue on 4.6) - make it 3000 miles between oil changes without needing oil added but it smoked enough let everyone know it had an issue.
 
No.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100?C (212 Fahrenheit)- or the operating temperature. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100?C etc.


http://www.driverstechnology.co.uk/oils.htm
 
(quoted from post at 20:51:04 11/12/18) No.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100?C (212 Fahrenheit)- or the operating temperature. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100?C etc.

Best of luck with your project.
http://www.driverstechnology.co.uk/oils.htm
Click to expand...
 
(quoted from post at 20:51:04 11/12/18) No.

In a 10w-40 for example the 10w bit (W = winter, not weight or watt or anything else for that matter) simply means that the oil must have a certain maximum viscosity/flow at low temperature. The lower the "W" number the better the oil's cold temperature/cold start performance.

The 40 in a 10w-40 simply means that the oil must fall within certain viscosity limits at 100?C (212 Fahrenheit)- or the operating temperature. This is a fixed limit and all oils that end in 40 must achieve these limits. Once again the lower the number, the thinner the oil: a 30 oil is thinner than a 40 oil at 100?C etc.


http://www.driverstechnology.co.uk/oils.htm
Click to expand...

Best of luck with your project.
 

I have a 97 F350 with the same 351W and well over 200K on it. Might use a quart every 3K. I think those saying a truck of that vintage and mileage needs a new engine are nuts. I'd try the regular dino oil as other suggest, get the PC valve checked and I'd park it on a real clean spot of pavement, or put a sacrificial sheet under it, and check it for leaks while running. Let it idle, rev it up, idle some more, get it nice and warm. I had a car one time had a tiny pinhole in the oil pressure sender. Didn't see any smoke but I changed everything from the valve cover gaskets to the rear main seal trying to stop that leak. had another car the oil filter actually rusted through. Point is, don't assume the engine is shot if you aren't seeing smoke from the exhaust. I've owned cars that burned a quart every 100 miles and trust me, you'd see the smoke!
 
I'll second a leak down test. Over-reving some Ford truck V-8s could crack the pistons across a ring groove.

Twenty years ago I had an '86 F150 with a 351 4 BBL that kept testing high on hydrocarbon emissions. The miles were around 105,000. I tried a tune up and the other easy fixes but they did not work. A Ford dealer could not fix it either, but in those days a $150 repair bill was enough that Minneapolis would let you keep driving it without passing their emissions test.

It kept getting worst and I left it with a small auto shop that had a reputation for good work. While the mechanic was warming it up there was a loud bang and the engine locked up. The top of one piston separated. I felt fortunate not to be driving it down the highway when it let go. The heads and crankshaft were still OK. I had the option to fix just the one cylinder, but did not trust the other seven pistons to hold up too much longer. At that time a rebuilt engine cost about what the 4WD pickup was worth after fixing it. In hind-sight, I should have sold the truck for salvage value without fixing it.
 

That's pretty much my experience - the older engine designs from the 1960s and 1970s doubled their mileage when they went to multi port fuel injection and over drive transmissions in the late 1980s and early 90s.


I'm thinking PVC or the rings-pistons got baked from the previous owner overheating it.

Like I said - it runs great with no extra noises, good power and starts easy. It seems when they have ring and piston issues they get down on power and have problems with cold starts. This one fires off on the first revolution of the starter. They also seem to leak oil and coolant like a sieve because the seals and gaskets all got hot along with the engine and get brittle.


This is the same truck we had the issue with it running extremely rich while throwing a code that it was running lean. We had two issues - a fuel valve in the fuel injection system was leaking a huge amount of fuel into a vacuum line and another vacuum line was cracked letting unmetered air in. At that time if you revved it up it would blow black smoke out the exhaust. With that fix it started running like I had hoped it would run.
 
I had this same problem with my first car, '70 Nova with 307 V8, used a quart of oil every 100-125 miles. Talked to a boat load of mechanics before one said it was the o-rings Chevy used as oil seals on the valve stems. He said engine had probably been OVER-HEATED a time or two, o-rings got hard and brittle and broke. I made an appt and took the car in on the way to work. He ran one side of the engine while I watched. Screwed a broken spark plug with air hose connector into plug hole, turned air on to hold valves closed, seals were missing on half the valves, broken and just sitting there on couple more. Install new o-rings, replace valve springs, and keepers, move air fitting to next hole and repeat. He did say my valve guides were pretty loose, another sign of the engine being hot. I drove the car over 500 miles before adding a quart of oil after that. Then between 350 and 400 for the 2nd quart, then 250, then settled around 100-110. I looked for better heads, better complete engine, traded the car for a new Firebird.
Engine didn't leak, didn't smoke, had good compression, didn't foul plugs. Actually ran like a raped ape!
 

That's pretty much my experience - the older engine designs from the 1960s and 1970s doubled their mileage when they went to multi port fuel injection and over drive transmissions in the late 1980s and early 90s.


I'm thinking PVC or the rings-pistons got baked from the previous owner overheating it.

Like I said - it runs great with no extra noises, good power and starts easy. It seems when they have ring and piston issues they get down on power and have problems with cold starts. This one fires off on the first revolution of the starter. They also seem to leak oil and coolant like a sieve because the seals and gaskets all got hot along with the engine and get brittle.


This is the same truck we had the issue with it running extremely rich while throwing a code that it was running lean. We had two issues - a fuel valve in the fuel injection system was leaking a huge amount of fuel into a vacuum line and another vacuum line was cracked letting unmetered air in. At that time if you revved it up it would blow black smoke out the exhaust. With that fix it started running like I had hoped it would run.
 
Sounds similar. Except I have a 16 year old kid driving it and I just know he's going to run it empty and fry the engine.
 
as has been said do a leak down , it could be a bad intake gasket but at that rate it has to smoke a little , take it out an mash it for a block and see if there is smoke
 

You can eliminate PVC issues check crank case pressure I know on cars the PVC goes into the back of the intake there is a filter under it that does stop up... I think trucks go into the valve cover right rear.

My 77 F350 used oil bad at 20K miles once disassembled the oil rings were worn out I have see the same issues on other 400's with low mileage. I had so much trouble with the original 400 there for awhile I could not keep a crank in it... I had a good bud that ran a engine rebuild shop build me one All was good till the top tank on the rad separated while on the interstate I ran it hotter than ell. From that point on it would burn a qt in 100 miles no smoke maybe a little when you started it but it ran great...

Those like yours were bad to burn holes in pistons #5 I believe and crack/break skirts on pistons... Running a engine hot is like having a stroke it will never be the same...
 
run a compression test and a cylinder leak down test. Those engines used low tension piston rings and things like bad pcv valves and overheating do not add to their life. It can burn a lot of oil and you will never see it because those jumbo catalytic converters . 140 K is a lot of miles on those engines, they were not machined to the tolerances of todays engines. Lose the synthetic oil, put good old 10w30 like the owners manual says, or even 10w40. See how much hissing you can hear in the crankcase when you do the cylinder leak down test, if you are using that much oil you should have some blowby overwhelming the pcv system and putting oil in the air cleaner.
 

Check for excessive crank case pressure FIRST (blow by) if excessive crankcase pressure no leak down test NEEDED... If its the oil control rings it may pass a leak down test and a blow by test...

EZ as pie, remove the PVC valve and plug it, plug the hole the PVC valve goes into plug off the crankcase vent (a tube that comes off the oil fill tube to the air cleaner) remove the oil cap crank the engine up lay you hand over the oil fill hole feel for positive pressure... Best done with a nitrile are latex glove on your hand to help seal off the oil fill hole...

If all is good you should feel no are very little positive pressure if bad it will blow when you re-leave the seal from the oil fill cap when you slightly lift your hand...

If it blows call in the family its not good for the home team... You are gonna get deep into it real deep if a willing player call in a cosigner...
 
That's not all that many miles like everyone seems to think. I had 3-4 late 80's -mid 90's Ford trucks. None had been overheated, but they all had been well used to their capacity. Only one had 144,000 miles, the others had between 200,000 - 275,000 miles on them. My 96 F250 has a touch over 301,000 miles, but it's a Powerstroke. I had a 92 Ranger, regular cab, short box, 4 cyl, 5sp, 4X4. I bought it from my brother with a new reman engine that had been setting for about 5 years. I put it in, but it used oil terrible, about as bad as yours. Never smoked at all, never leaked, just disappeared. Do you suppose when your truck was running so rich that it maybe washed a cylinder down with gas and ruined a cylinder or 2?

Ross
 
"Could the oil ring be letting this much oil by while the compression rings are still doing their job?"

Yes they can. I drove a 79 Chevy with a 250 that burnt oil like that. It had wear like I have never seen before and the #1 oil ring was broken. I've worked on a lot of motors and that was a first. All the oil rings were weak.

I rung it when the compression rings got weak and it took the oil usage to reasonable levels.

RT
 
1 quart in 200 miles

30 MPH average speed

6.6 hours to a quart of oil

Guess around 15 MPG

13.3 gal gas to 1 quart oil

Works out to about 2 oz oil per gallon

or 4.8 oz per hour

If it was all going out 1 cylinder it would have a fouled plug and be running poor so that suggests the oil is being consumed somewhat equally by all the cylinders.

Going past the valves there should be noticeable smoke on cold start up.

PCV, glazed or weak rings or intake gasket problem would seem most logical.

Many an engine will use no oil after a fresh oil change then 4-5000 miles later start to show high consumption and require continuous addition of oil.
Change oil and good for another 4-5000 miles.
 
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