How much oil can a 5.3 LM7 burn

Enroute

Active Member
Great to be a new member of this site. Amazing knowledge going here. 5.3L 2002 Silverado LS 210,000 miles with a huge hunger for oil. 2+ qrts and not even 2000 mile between changes. Replaced valve cover gaskets (old one version with the holes and removable fixed opening) to begin the process of finding a leak (hopefully it is a leak) and top of heads super clean, rockers free and no sludge in valley (PO and I have been religious on oil changes every 3000 miles with 5W-300). Top down method per many threads here. Will continue the process once my torque Pro adapter comes next week to get some readings.

Have read many threads and watched hours of videos outlining the PCV issues with these motors but a crude catch can really did not catch much after replacing VC gaskets. Can the PCV issue really use that much oil? Really do not see any spots on the ground and back of engine is clean but the front seems oily but the skid plates are in the way. Love the truck and engine but not the cost of the oil every two weeks. Here is the real question, where do I start this quest? Pull the skids and clean the front of the engine with brake cleaner to try and track the leak or pull the plugs, (70,000 on them). I have limited time and money to invest but lots of desire to learn and investigate. Will not just sling parts at it but the oil is getting a bit much. Thanks ahead of time for all your help.
 

MRRSM

Lifetime VIP Supporter
Depending upon the Mileage and Condition of the Motor (Bad Cylinder Compression, Evidence of a Serious Gas Blow-By from the Strong Smell of Gasoline on the Dip Stick, Nominal Engine Oil Consumption should be around:

1 Quart Every 2,000 Miles.

While NOT covering the NON-DOD LM7 Engines in this TSB involving the Problem of Excessive Oil Consumption with 2007-2012 Model Aluminum and Cast Iron Engine Blocks, Nominal Oil Consumption of 1 Quart per 2,000 Miles is mentioned.

It is probable that the necessary burning of Motor Oil in the normal operation of the GM 4.8L, 5.3L and 6L Engines is likely pretty similar in well cared for and maintained General Motors Engines.
 

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Enroute

Active Member
Thanks for the info. I did read this TSB previously and found it very helpful. I am on my way to 3 times that amount. Here are some things I have noticed after checking oil levels and other fluid levels almost on a daily basis.

1) oil stays clean, clear and no gas smell. No discoloring-great thread in here about that as an indication of a blown head gasket or cracked head.

2) Both long and short fuel trims are great for an engine with 210,000 miles. Mostly down below +5 and always in the single digits. Gas mileage calculation at the pump at fill up is 13 on average. Seems low from what I have read in here.

3) no other fluids show any sign of loss

4) white (not bright white) almost grey smoke at startup (no way near blue or black). Pretty much goes away after engine warms. Leads me to the valve seals per another thread in here.

5) According to the old BlueDriver app, it will pass the smog test

Am I on the right track? Will pulling and replacing plugs give me any real diagnostics results or am I moving towards a compression test or would a leak down test serve me better? Still am not sure if pulling the skid plates and cleaning the front of the engine to find a leak might better serve my limited time availability.
 

northcreek

Well-Known Member
At 210,000 miles and depending if the miles were hard miles or amassed 1/4 mile at a time, this might be the signs of an engine in need of a rebuild. In other words there are no easy fixes.
 
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Enroute

Active Member
Thinking that way too! It is a farm truck to pull hay bail wagons in and out of fields. Was hoping for just a little more time from the old girl. She has been good to me. What is the thoughts on the Lucas heavy duty oil stabilizer?
 

TollKeeper

Well-Known Member
What is the thoughts on the Lucas heavy duty oil stabilizer?
Personally.. Its junk. Its known to aerate the oil, and where there is no oil, there is going to be damage.
 

northcreek

Well-Known Member
Thinking that way too! It is a farm truck to pull hay bail wagons in and out of fields. Was hoping for just a little more time from the old girl.
You might want to try that 3hr. top end cleaner process before you do anything else, I guess some people have had success doing that.
 
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Enroute

Active Member
Really thought the plugs were going to tell me a story but to no avail. Was hoping that one or two were going to be all black and covered in oil. I will take pics and post tomorrow when I get them all lined up. Mostly grey with a bit of build up. Seems to have a little more pep after plug change. Can not wait for my ELM327 to arrive on Wednesday to begin looking for some misfires as there is a slight hick-up at idle. LT Fuel trim remain low in single low digits albeit positive.

Here is the good news and bad news. Spent the afternoon cleaning the underside of my engine trying to track down an oil leak that looks like it was the front pan gasket. Used the foot powder trick I read in a thread in here. Do not remember which but it worked great.

Good news it was not. Not a drop from in front at all. So maybe it is the power steering pump or front differential that put so much stuff in the front after the fan blew it all over the place. Left the skid plates off to keep an eye on it. Bad news, leak from rear of engine on drivers side up top. Oil pressure sensor I am pretty sure. The dash display bounces a lot so will replace tomorrow after a manual gauge verification as was suggested in here as well. Looks like a pretty good amount was flowing. More bad news depending on how bad the oil pressure sensor was leaking, that this latest investigation means it is the motor that is burning the oil. Will stay away from the Lucas but will try that three hour top end cleaner to see if it helps. Next step is a leak down test per threads in here. Will see! Thanks again guys for all the great info. Trying to be methodical with this as advised.
 

MRRSM

Lifetime VIP Supporter
On Very High Mileage Engines... the next logical place to cause Direct Oil Consumption on the LM7 is Failing PTFE (TEFLON) Valve Stem Seals. The Oil present under the Valve covers pours through the Hollow Push Rods, lubricating and decorating the Roller Rockers can be slung or pool around those Valve Stems-To-Valve Guide Seals at around 5 up and down strokes per second at Low Idle.

After the Engine Oil POOLS around the Seal Lip, it gets vacuumed out along the Valve Stems with each Intake Down Stroke and it gets gets burned in each Cylinder right along with the Fuel-Air Mixture.

The Biggest Clue that this may be where all the Engine Oil is disappearing is the presence of the Slate Gray to Light Blue Color in your Exhaust Out-Gassing. These events are more prevalent in Idling Engines.

You've seen this from observing those Blue Plumes of Smoke from Vehicles stopped at Red Lights that billow out the stuff when the light turns Green and then the Blue Smoke Cloud gradually dissipates at Higher Engine RPM as those vehicles reach Highway Speeds.

With the Valve Train moving at 50 Xs Per Second Up & Down at 6,000 RPM, the Motor Oil can No Longer Collect and remain in between between the Valve Stems and the TEFLON Seals.

If you want to see all of the Tools and Processes required for doing this repair, Please ... visit my "Hoping For Loping Thread" covering the Performance Upgrades on my 2000 Chevrolet Silverado (Y2K Blue Truck):

 
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Enroute

Active Member
As promised, here are the pics of the plugs taken out yesterday. Originally did not think they told me much but after thinking more about the valve seals, #3 really caught my eye. Further inspection really tells a story after reading more threads and comparing to plug diagnostics picture charts. Very concerned that 4 & 6 have oil stains all up the threads confirming they were not tight as I remember as I took them out. Had to really twist the others to get them out but 4 & 6 took no effort at all.

Question, with 70,000 miles on these plugs would #3 have this kind of build up with just bad valve seals or does this nasty thing indicate a much worse condition? Trying to make a decision to take the heads off or just do the seals on #3 with the heads left on the block. Feeling pretty confident that I could do the R&R for #3 myself after reading the threads in here.
 

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m.mcmillen

Gold Supporter
The valve cover on the drivers side is known to colllect oil in the area where the pcv hose goes in. There isn’t an easy way to clean it but most parts stores stock the cover. I’ve changed the cover and solved oil consumption problems.
 

MRRSM

Lifetime VIP Supporter
I like @m.mcmillen 's idea on how to solve this problem MUCH Better than mine... AND it will be a whole lot less mechanically risky and involved to perform if your oil consumption stops afterwards:


Genuine GM 12570427 Valve Rocker Arm Cover:

GMLSENGINEUPDATEDVALVECOVER1.jpgGMLSENGINEUPDATEDVALVECOVER2.jpg

UPDATEDGMVALVECOVER.jpg

 
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Enroute

Active Member
Thanks for that. I did a test with a crude catch can after replacing the VC gaskets and a new PCV valve and it did not catch much. Definitely not to make up for the amount being used. I agree it is much less risky and the new design covers are readily available. Still really concerned about the #3 cylinder to have a plug look that bad. All the others seem to not really show that much oil burn.
 

MRRSM

Lifetime VIP Supporter
Modern GM Engines sports Compression Rings with VERY Low Spring Tension on them. Unlike the thicker, more ridged rings in the Old 265, 283, 327 and 350 CID Engines of Yore.... the Later Model LS Engine Compression Rings tend to STICK TIGHT inside of the Piston Lands & Grooves if the Upper Combustion Chamber is cluttered up with Excess Carbon Deposits. The rest of your Spark Plugs really Do NOT look Too Bad.

The easiest response would be to use either ACDelco Combustion Chamber Cleaning Spray:



... or perform the more complete method of using the BG44K Top Engine Cleaning Method:



Likewise, the similar procedures using spraying in the ACDelco Top Engine Cleaner in the Foam flavor is another option....However... THIS stuff does NOT get sprayed into a RUNNING ENGINE. The Spark Plugs should be removed and then the ACDelco TEC Foam is sprayed into the Combustion Chambers and allowed to sit for no longer than THREE HOURS. After that, with the Fuel Pump Relay removed ...BEFORE re-installing the Spark Plugs... the Engine MUST be turned over enough to evacuate the Cylinders of this Liquid... or you'll risk Hydro-Locking the Engine.

2-3 Cans of this stuff will be required on a V-8 Motor:

 
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Enroute

Active Member
Great advise and will give that a try. Thank you. Are you thinking my valve seals are still bad given the start up smoke and oil consumption? Could I be eating up that much oil in one cylinder #3?
 

MRRSM

Lifetime VIP Supporter
Not after reading about @m.mcmillen 's Revelation... in fact ...his information prompted me to get the GM OEM Updated Driver's Side Valve Cover for my 2000 Chevrolet Silverado 1500 ordered via Amazon as it also sports the LM7 5.3L Engine like yours.

Good Science means that you should "...Only Change One Variable at a Time...". So if you follow on with his suggestion first... Give it enough time to be evaluated before doing the complicated repair involving changing the Valve Guide Seals.

I'd only consider doing that job if the ACDelco Top Engine Cleaning had no effect on improving Compression and stopping the excessive Oil Burning caused by the errant GM OEM Valve Cover. So take these things... One Step at a Time.
 
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Enroute

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I did the same. Bought it today. Will install and continue to monitor oil levels and update. Pretty cheap fix if this is indeed the cause. Thanks again for all the info.

Pulled the passenger side valve cover vacuum breather tube that connects to the throttle body. Liquid oil drained from the throttle body connection. Can not be good for the throttle body to have that. Any updated technology on that? Will remove and clean throttle body real well and reinstall. It is drive by wire throttle so it may take a little while for the ECM to relearn that throttle body position. Any thoughts?
 

MRRSM

Lifetime VIP Supporter
After changing out the Old Spark Plugs... Give the New Ones enough time to 'clean up' the interior of the cylinder and then be watchful for the possible return of any P0300 Random Misfire Codes.

Ordinarily, disconnecting the Negative Battery Cable for 30 Minutes (Minimum) should allow the PCM-ECM to reset and clear itself and after a few Drive Cycles... relearn and make the requisite adjustments to a Cleaned Up Throttle Body.

Your 2002 vintage 5.3L LM7 Engine SHOULD have the Dual Cable Throttle Position Controls... but don't be tempted to fiddle around with the tightening adjustments there unless you can actually eyeball that the Cables look like they are about to slip completely off of the Guide Grooves in the Bell Crank. Having the Cable Tension a little loose is best in this situation:
BBKMODEL17090R12.jpgBBKMODEL17090R15.jpgBBKMODEL17090R14.jpgBBKMODEL17090R10.jpgACDELCOTPS1.jpgACDELCOTPS2.jpg
DELPHIIAC.jpg
If the Engine still runs rough after all this... something else is amiss. A "GYMKO"Tech 2 Scanner really is your BFF here if you are lucky enough to own one... or get the latest Full Tech 2 Kit via eBay that seem to be available for around $200.00.

Oh... and about "Getting Engine Oil into the Upper Cylinders..."

Actually, contrary to "The Mechanical Arrogance of 'Modern Engineers'...", if you hearken back to the earliest days of the Engines installed in the Big Cadillacs and The Hudsons of the 1930s-1950s,.. many of them had devices that looked like the Old Railroad Engineer Re-Fill-able Glass Bushings, Bearings and Gimble Lubrication Dispensers.

These "Inverse Oil Dispensers" fitted with Glass Reservoirs were piped out like Brake Line Master Cylinders directly into the Carburetor Venturi using the Natural Vacuum around that area of the Intake Throat. This vacuum event would draw the Lube into the Fuel-Air Stream; mixing with both and protecting the Upper Cylinder Head, Valves and Rings. Of course, these devices required getting topped off at regular intervals and filled with... Wait for it... Marvel Mystery Oil... in order to provide an assist with necessary Top Cylinder Lubrication.

So having Oil ingested into the upper cylinders a few drops at a time seriously prolonged Engine Life almost a Century ago and was INTENTIONAL, BY DESIGN. The Moral of The Story here being that getting Light Lube Oil into the Engine Upper Cylinder Head and around the Valves and Rings inside ANY Motor in quantities insufficient to cause Hydro-Locking events ...is NOT necessarily a Bad Thing.

It's a shame that the majority of the 'Fashionable Puppies" growing up today with Cell Phone Screens stuffed in front of their faces and suffering Sore Thumbs from Key-Pad overuse could not have grown up in a North America at a time when we had REAL Mechanics working in the "garages" of almost EVERY Corner Gas Station.

Those Folks were the ones who worked on Machines that had much Beauty and Elegance and did so with Basic Tools and Common Sense. MAN... if only they knew what they are missing by not being able to get their hands Greasy and Dirty and learning how to breathe life into Dead Machinery.

MMORESERVOIRADVERTISEMENT.jpgMMORESERVOIR.jpgHUDSONSUPERCHARGEDENGINE.jpgSUPERCHARGEDENGINEWITHMMODISPENSER.jpgMMORESERVOIR1.jpgMMORESERVOIR2.jpg



"Jesus... The Days We Have Seen...Master Shallow..." (Act 3, Scene 2 "Henry the 4th" by William Shakespeare... Sir John Falstaff, lamenting with a friend around a Fire Side about Long Gone Days...)
 
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aaserv

Well-Known Member
I wouldnt discount how much oil you could be losing with a leaking pressure switch. runs down the back of a hot motor and may pan fry on top of the tranny or be hitting the exhaust and burning off so you hardly see any on the ground.
Also something I was concerned about on my 2003 but have no idea about technically , the PCV valve on mine isnt a "valve" at all. Meaning it has no ball in it like every other 1 Ive ever seen. I would think and Im sure Ill be corrected if Im wrong but under the highest vacuum conditions, high enough to suck oil out the valve covers, the ball should rise up and block the hole momentarily to help keep that oil out the system. That makes a lot of sense to me but apparently not to GM engineers who Im sure know more about it than I do ....Still i found 1 with a ball in that fit but I havent come close to putting enough miles on it since to say if its done anything at all......

I used Lucas in my 2010 4.8 w 280k and thought it worked well. I did lose an oil pump about a year later but hard to say thats what caused it. The secret is to add it slowly to a hot engine and then drive it a good 20 to 30 mins immediately to make sure it blends and doesnt just sink to the bottom of the pan..

Another thing I have no experience with but remember an old school mechanic used to recommend many years ago was simply switching oil brands. If the vehicle had run say quaker state for years and was using oil the 1st thing hed say to try was switching to valvoline or castrol or whatever. Again no idea if it ever helped anybody but cant hurt a thing to try it.........
 

Mooseman

Moderator
On the V8's, do not clean the throttle body unless you do have a Tech 2 or high end scanner capable of doing a relearn. Unlike the I6, the V8 has an entirely different procedure and may cause issues without it. @MAY03LT has a video on this on YT.
 
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Enroute

Active Member
I did see that YT video but thought it was for throttle bodies that were opened and closed by the ecm. I miss quoted in my last post that my LM7 was a DBW throttle body. It is not. It is a drive by cable. Can I get a clarification on that understanding that a DBC throttle body does not need to have the relearn process done? I have not done the removal and clean yet so this is very important to get straightened out. Appreciate all the help.
 

m.mcmillen

Gold Supporter
There is nothing to relearn if you have cables. The reason you need to do relearns on the drive by wire ones is because they use the butterfly valve in the throttle body to regulate engine speed at idle and it is constantly learning. When you clean those out, you throw that calculation off and most times will idle too high.

The non drive by wire has an air bypass valve in the throttle body that regulates engine speed at idle so there is nothing to relearn there.
 
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Enroute

Active Member
Perfect. Thanks so much for the clarification.

My scan tool sometimes says the throttle position is 0.00% at idle and other times it says 0.39%. That is what indicated to me that it needed to be cleaned. My calculated load at idle seems high at 1.97 and fluctuates down to 1.56 and then back up. Based upon reasearch, that could indicate a faulty MAP sensor. My MAF reading at idle is above 5 which seems high to me as well. Always thought it should be around 4.8ish at idle. Any thoughts? Chasing down rough idle issues but fuel trims combined are below 5.

Not to go off topic so I will limit my conversations to oil loss. Taking post #19 to heart. Replacing oil pressure sensor and the redesigned drivers side VC today. Will monitor and advise. Great stuff guys! Thank you so much.
 

Mooseman

Moderator
Oooops. My bad. :duh: Thought it was drive by wire.
 
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Enroute

Active Member
No worries. As stated in my post #22, I miss stated in my post #17 that my throttle body was a dbw. I always appreciate the information.
 
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Enroute

Active Member
Good day guys. Time for an update. “One step at a time” as I have been told.

Installed the new OEM valve cover middle of last week. Watched oil consumption and smoke at start up over the next few days. Slowed consumption down and reduced the smoke at startup. Did not completely solve the problem.

Replace the leaking oil pressure sensor this past weekend. A royal PITA. All by feel and cut up my hand pretty good having to reach back behind the intake. Had the special socket but still broke the sending unit on the old one trying to take it out. Threaded new one hand tight and snugged it down. Glad I never have to do that again. Seems to again slowed consumption down a little more but no reduction in smoke at startup or after long idle. Will continue to monitor consumption and smoke.

After reviewing many posts all over the web, I am pretty confident that I have bad valve seal on cylinder #3 based upon the condition of that spark plug as pictured in post #10. All other plugs seem to be indicating normal wear but #3 really indicates serious build up left from oil being burned off and leaving the deposits on the plug. What are your thoughts on doing the valve seals, both intake and exhaust on just one cylinder? LTFT are higher on bank 1 but still below 5 most of the time. LTFT Bank 2 is almost zero most of the time. Question, can one cylinders valve seals really leak that much or should I bite the bullet and do all bank 1cylinders while I have the valve cover off? Is that taking “one step at a time” too much to the extreme?
 

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