High oil consumption on 2001 Toyota Highlander- 3.0 V-6 engine

Question edited for a lot more clarity.
Question moved to 'make and model' for the engine.

No that is the last thing it is likely to be! It was working before, why would it fail because you changed the valves?

Did you carefully lap the new valves with grinding paste to make sure they sealed? Are they all opening a closing. Is the gap correct?

Can you do a compression test?

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Jun 21, 2021 - Power loss; Poor engine operation. Excess oil consumption is generally anything over 1 quart per 1,000 miles. As oil blows-by the piston rings ...

2004 , no miles on engine, stated, (odometer) 50k, 500k, what?
all engines burn oil by design. ALL !
only question is, how much, ?
miles /per quart
or KM per LITER.

if you ask any sharp mech, to fix oil consumption, HE WILL
Ching-ching..... after all you asked him, !!!!!
don't , no really dont.

post the consumption rates and ask.?
ive got like 1.5million miles in cars, and motorcycles.
and 300k or more in ships. (our ship burns oil only) LOL

the number 1 reason of excessive oil is driving too fast.
if you drive most cars 80mphy all the time, it will burn more oil
most cars new run about 1 quart of oil per 3000 miles.

I had one engine, a mazda, i drove it to the ground, as an experiment.
a 626, it was using a quart every 1000 miles
it took oil EVERY fill up. oils cheap so I fed it. why not?
the PO overheated the engine once and that is why.;
I rebuild engines so , know the reasons.... (retired now)

does tail pipe end smoke? , (end) first start, not steam,but oil smoke)?
only cold, ignore it.
does it hot?, its got issues. (rings)
if it loves toSMOKE , going down a hill fast?, and with foot off throttle
(high vacuum) and you look in rear view mirror and it's smoking
yes, that is valve seals bad, $10 in parts.
ask someone to follow you, and look for smoke, (easy,huh?)

if it smokes all the time?, and PCV valve is new (not clogged)
it needs rings. or like me, just drive it like you stole it, why not?

Google search GM 5.3 oil consumption. This is a known and common issue.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

Hi,normaly if the stem cills are worn it would smoke on start up,as when the engine is switched off oil will pass the cill and couse a puff of smoke untill the oil burns off,it could be that the head gasket has a falt where oil leaks strate into one of the cylinders,or maybe the where the car had not been started for awhile the piston rings might have frosen a bit,you could try a engine flush and see if that helps,in the past I have used a aditive called slick-50 which gave good resalts,remeber as I have not seen the car this is all food for thought,hope this was some help,hope you sort it.

One quart per month is a bit more than I'd expect but you didn't mention how many miles you drive during that month.If you live where the ambient temps are very warm, it may help to use a good synthetic. Synthetic oils do not burn off or break down chemically as fast as conventional oils do. I'd use a 20w40 grade.
Depending on the miles you've driven you shouldn't have excessive ring wear but the valve stem seals may have dried out and cracked. If the usage remains constant and there is no smoking etc, you could either leave it alone or have new seals installed.
Average driving is approximately 1,000 miles per month so when figuring consumption, use that as a baseline. One quart per 1,000 miles in very hot conditions is a bit high....I'd expect to see 1/2 qt or slightly less. One odd thing though is that generally, especially in an engine that holds six quarts to begin with, at five quarts, the engine should not feel any different!!!
Also.....you use miles to determine oil change intervals. Oil is best changed at between 3K and 4K miles. Only way you use the 3month method is if you don't use it much. (you can run most good synthetics longer than that)

the best way to find a oil leak is to get a better look go under the car and look at the oil pan for any signs of leakage open your hood and look around the valve covers and intake for leakage these are the normal places oil will leak from first. second i would watch the exhaust for white or blueish white smoke and third i would pull the plugs to see if there is oil being burned.

It is good for your engine.

You have a good maintenance culture.

Cheers and rate this.

hi, the main cause of major oil consumption is due to cylinder wall deterioration. this is caused be bad piston ring sets that tend to chip of tiny pieces of the cylinder walls over a long period of time. this will start to show in engines with high millage. this will also lead to compression loss as well if it is not fixed soon.

To fix this issue within the cylinder walls, they will have to be machined and a new set of piston rings will have to be fitted around each affected piston. this will stop the oil from leaking into the combustion chamber and it will restore the compression rate as well.

Replace your valve covers do to clogged pcv piping

Every manufacturer has a guideline.  But a quart every 1,000 miles seems higher then necessary.  Try the easy steps first. 1.  Check the PCV valve if clogged will caused pressure in crankcase and oil burning. 2. Remove spark plugs and perform visual inspection.  IF electrode is covered in gook(technical terms, sorry), then oil is leaking into that cylinder.  Most likely cause would be faulty valve stem seals. 3. Worse case scenario, engine oil rings are leaking.  If all else is good.  Perform compression test of each cylinder recording measurement, then add two small squirt of engine oil into each cylinder as you perform a second round, complete both dry then wet compression test on each cylinder before proceeding.  IF any cylinder shows a more significant increase in compression then it would indicate that cylinder's oil rings are faulty.  This is a major repair.  Keep me posted