Automotive

Why do Cars Burn Oil?

  • Last Updated:
  • Feb 27th, 2018 4:28 pm
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[OP]
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Aug 3, 2014
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Toronto, ON

Why do Cars Burn Oil?

One of the common problems with (beige) Corolla's recommended here is that they burn too much oil.

I took apart a 1ZZ-FE engine and explained why they burn so much oil and made a short video on it:


The two main causes of engine oil burning are piston rings and valve stem seals.

Here's a break down of the engine's piston head and its rings:
Image

The problem on many cars (including Corolla) is the engine runs hotter than it was designed for, causing the petroleum inside the oil to break down and cause sludge and carbon buildup. The carbon blocks the oil return holes in the piston head, and the oil that's scraped off the piston walls has no where to go, except up, into the combustion chamber, where it gets burned!

Here you can see on my Corolla with 200,000km the carbon building up behind the oil control ring:
Image

Here is the three parts of the ring - that center springy part is supposed to be free and easy to move, collect oil and allowing to drain into the piston head. Instead it just gathers carbon and clogs up.

Image

The second way cars can burn oil is valve stem seals.
Valves separate the well lubricated top half of the engine from the combustion side of the engine. The seal between them will get dry, crack and leak after many miles and heat cycles. This causes oil to pool onto the pistons overnight, causing blue smoke at startup in the morning:

Image

There's no easy preventative maintenance you can do to stop the piston rings from getting carbon buildup. The ultimate solution is to drill more holes into the piston to allow more oil to flow through the rings, but that pretty much requires an engine rebuild!

For more on engine oil lubrication, see my video and thread where I explained how it worked here:

https://forums.redflagdeals.com/how-you ... s-2123882/

Hope it gives you some insight. Enjoy!
_______
Speedkar99 | YouTube
10 replies
Deal Guru
Feb 9, 2006
10459 posts
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Brampton
Funny because the 1ZZ isn't known for oil burning. Its the 2.4L 2AZ that burns more oil than an old Honda engine.

There's also the issue of when the PCV clogs and excess crankcase pressure results in more than normal blowby.

Good explanation none the less
Last edited by tebore on Feb 26th, 2018 8:12 pm, edited 1 time in total.
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Aug 2, 2004
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East Gwillimbury
You're getting quite an education from this Corolla. I think it was money well spent.
[OP]
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Aug 3, 2014
1218 posts
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Toronto, ON
iflyplanes wrote:
Feb 26th, 2018 7:20 pm
Upvote for beige Corolla.
george__ wrote:
Feb 26th, 2018 8:14 pm
This is so neat
Gee wrote:
Feb 26th, 2018 8:18 pm
You're getting quite an education from this Corolla. I think it was money well spent.
Thanks!

It sure was money well spent, I am still learning a lot from it. So much so I'm thinking of buying another scrap car to gut out this summer... any suggestions?
tebore wrote:
Feb 26th, 2018 8:12 pm
Funny because the 1ZZ isn't known for oil burning. Its the 2.4L 2AZ that burns more oil than an old Honda engine.

There's also the issue of when the PCV clogs and excess crankcase pressure results in more than normal blowby.

Good explanation none the less
The older 1ZZ from 98-02 was a killer for oil consumption. You can see how the oil ring is clogged.
From 2003-08 the issue was fixed.
_______
Speedkar99 | YouTube
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Jan 8, 2009
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Ontario
tebore wrote:
Feb 26th, 2018 8:12 pm
Funny because the 1ZZ isn't known for oil burning. Its the 2.4L 2AZ that burns more oil than an old Honda engine.

There's also the issue of when the PCV clogs and excess crankcase pressure results in more than normal blowby.

Good explanation none the less
There is a warranty extension program in Canada to cover the 2AZ defective piston issue but Toyota makes it very difficult to get repairs or compensation for repairs. I have been waiting years for a refund of the cost of rectification despite getting a notice from Toyota in April 2015 saying they are initiating "a reimbursement program for previous repairs related to this condition". Toyota have so many engines affected by this that i think they cannot afford to fix them all. It should be a recall as the engines can run out of oil and seize on the highway. There is no indication of smoking before the no oil pressure light comes on then it is too late.
"Never wrestle with a pig. You'll both get dirty, and the pig likes it"
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Aug 2, 2004
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East Gwillimbury
speedkar9 wrote:
Feb 26th, 2018 8:32 pm
It sure was money well spent, I am still learning a lot from it. So much so I'm thinking of buying another scrap car to gut out this summer... any suggestions?
Sounds like you're already a master mechanic. Try finding an old Subaru. It is a different engine configuration. Horizontally opposed cylinders. I am sure you will have fun learning about their all wheel drive as well.
Jr. Member
Jan 22, 2017
139 posts
60 upvotes
You are doing gods work.

Long live the beige Corolla.
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Nov 4, 2008
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Richmond Hill
speedkar9 wrote:
Feb 26th, 2018 8:32 pm
So much so I'm thinking of buying another scrap car to gut out this summer... any suggestions?
I think an RX8 would make for a great teardown/fix-it-up project
When given enough time, all threads on RFD can and will go off on a tangent.
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Feb 29, 2008
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Montreal
I thought it was feature of VW-AG 2L turbos

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