Low oil mystery
11-20-20, 05:49 AM
#1
Driver
Thread Starter
Low oil mystery
A few months ago, I drove my 2008 is350 as usual to town to run errands and the 'low oil' warning came on. I stopped, checked the oil, and it was near the low point on the dipstick. This was frightening as while it has 145,000 miles on it I've never needed to add oil. I filled the oil and drove home. Two days later it did the same thing and I gave the car immediately to my mechanic to diagnose what's happening.
My mechanic is so far stumped as it's been fine since then. All maintenance has been pretty much done following the manual. He pulled one spark plug and it wasn't fouled and looked good. There are no engine codes, and a pressure check showed the engine good and tight. The car has been driven regularly since then and the oil has been fine. I'm worried I'll take the car on a long trip and it will suddenly have 'low oil' problems somewhere where I can't immediately stop.
What could be causing this? What things should be checked to narrow down possible causes?
My mechanic is so far stumped as it's been fine since then. All maintenance has been pretty much done following the manual. He pulled one spark plug and it wasn't fouled and looked good. There are no engine codes, and a pressure check showed the engine good and tight. The car has been driven regularly since then and the oil has been fine. I'm worried I'll take the car on a long trip and it will suddenly have 'low oil' problems somewhere where I can't immediately stop.
What could be causing this? What things should be checked to narrow down possible causes?
11-20-20, 06:21 AM
#2
So when it threw the low oil pressure light the second time, did you check the dipstick and where was it at? So oil can only go two places, into the combustion chamber and leak out into the engine bay. Sounds like you have a healthy motor and you're not pushing blue smoke out the exhaust. So it would lead me to believe you're leaking it somewhere. What I recommend doing is removing the entire lower plastic engine/dust/debris cover and inspect. If nothing stands out, put a large piece of cardboard under the engine area over night and see where the oil leaks onto it.
Good luck and report back when able!
Good luck and report back when able!
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ncatona (12-26-20)
11-23-20, 06:40 AM
#5
Driver
Thread Starter
This year the vehicle is driven once or twice a week to run errands and get groceries. Each trip means driving about 2 miles to exit town, around 15 miles on a highway at 65mph, then city driving from 30mph to 50mph.
Each time it was low, it was at the bottom mark on the dipstick. I'm going to visit the mechanic today and get an update on what he's found so far, so I'll verify he's inspected underneath already.
Each time it was low, it was at the bottom mark on the dipstick. I'm going to visit the mechanic today and get an update on what he's found so far, so I'll verify he's inspected underneath already.
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ncatona (12-26-20)
11-23-20, 10:11 AM
#6
Those sound long enough for it to reach operating temp. You might dump some fuel treatment in it and open it up (only when known to be full of oil).
For peice of mind I would pull all the plugs and do a compression test. That said, if the consumption is through the valve guides, it won't show up here on a compression test but will on show as blue smoke after deceleration and upon applying the throttle again. Keep an eye in the mirror. i.e. on a long down hill grade at hiway speed, shift to say 4th, do some engine braking for say 10 seconds, then apply throttle while looking in the mirror.
For peice of mind I would pull all the plugs and do a compression test. That said, if the consumption is through the valve guides, it won't show up here on a compression test but will on show as blue smoke after deceleration and upon applying the throttle again. Keep an eye in the mirror. i.e. on a long down hill grade at hiway speed, shift to say 4th, do some engine braking for say 10 seconds, then apply throttle while looking in the mirror.
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ncatona (12-26-20)
11-23-20, 03:13 PM
#7
Driver
Thread Starter
Update from mechanic today: No oil leaks found underneath, so this is oil being consumed. Twice this last week it ran very rough when starting, then cleared up and ran normally. He's seen an intermittent PCV valve cause this where once in a while it sticks and dumps oil into the intake. Still no codes, so he's going to replace the PCV valve and see if it's fine afterward.
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ChudiM (11-25-20)
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12-18-20, 02:25 PM
#8
Driver
Thread Starter
Update from mechanic shop: Work got delayed and the chief mechanic who was working on my car has Covid and likely won't be back this year. How hard would it be for me to replace the PCV valve myself?
12-18-20, 02:41 PM
#9
12-24-20, 06:38 AM
#10
Driver
Thread Starter
Worked with another mechanic at the shop, removed the old PCV valve and it didn't look too bad or extremely dirty. Decided to replace it with one from the dealer anyway, finished that and drove it home. I'll keep extra oil in the trunk for a while and hope the problem is solved. For now, I'll try to check the oil levels when adding fuel.
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ncatona (12-26-20)
12-26-20, 11:16 AM
#11
Intermediate
12-26-20, 06:00 PM
#12
Driver
Thread Starter
Basically, the Lexus is taken on one or two trips each week of 40 to 80 miles each. I'm in a small suburb, so any trip is about 50% highway to get to the metro area and then 50% city streets. Each trip may include two or three stops such as for groceries, dentist, etc. The car sits outside year round in Iowa with cold winters and somewhat hot summers.
Each trip is typically some city streets to get to the highway and get the car warmed up a bit. Once it's at full temperature, I switch between normal and ECT (power) mode based on traffic levels. Maybe one every other trip or so I'll use full throttle getting from a side street onto the highway going from 30mph to about 70mph as fast as possible.
Each trip is typically some city streets to get to the highway and get the car warmed up a bit. Once it's at full temperature, I switch between normal and ECT (power) mode based on traffic levels. Maybe one every other trip or so I'll use full throttle getting from a side street onto the highway going from 30mph to about 70mph as fast as possible.
Last edited by bryan11; 12-26-20 at 06:12 PM.
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ncatona (12-27-20)
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ncatona (03-19-21)
03-19-21, 11:18 AM
#14
Intermediate
07-31-21, 06:43 PM
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low oil mystery
I have a 2008 LS460, 166k miles, has been losing engine oil 1qt after driving about 1000 miles. No engine lights at this point. My machanic says it's more feasible to keep checking and adding oil every 1000 miles than finding out the causes, and I have been doing it over a year now. I wonder if you shall try to change the PCV Valve? Any input is appreciated!