Burning oil

[Mrt23]

So I bought an is250 one year ago and I have put in 6l of oil. My last is200 I never put in anything apart from services.

some people have said this is standard and others have said it’s very bad news.

Would anyone know if this is normally the stem seals or the pistons? 
im not very mechanically minded and I don’t really want to get rid of the car.

I don’t mind paying a bit to get it sorted but not thousands.

it’s just past it’s MOT but emissions picked up due to oil.

any help/advice would be much appreciated 🙏

[is200 Newbie]

Its not normal, whats the mileage?

[Mihanicos]

Assuming you are using the correct type and viscosity of oil, and depending on your driving style, daily trip lengths, ambient temperature, terrain of driving and load, some oil will be consumed by any healthy engine.

Make sure you are using the correct ACEA C rating of engine oil. This rating depends on the High Temperature Shear Viscosity of the oil. Using the wrong HTSV oil will cause engine damage.  See ACEA oil specifications.

Check the compression of each cylinder. Worn piston rings and an engine that overheated will cause oil consumption.

Worn valve seals will also cause engine oil consumption. It is possible to change them without removing the cylinder head.

Inspect the spark plugs. A healthy engine will have the electrode porcelain colour light chestnut brown, indicating a stoichiometric combustion. An oily and sooty electrode indicates excessive oil consumption either from the piston rings or the valve seals.

Some engines other than Toyota and Lexus are designed to burn oil  about 1.5 litres per 1000 miles for normal driving conditions. The reason for this is to improve fuel economy at the expense of blocking the catalytic converters.

Chris.

[Mrt23]

10 hours ago, is200 Newbie said:

Its not normal, whats the mileage?

98,000

[Mrt23]

2 hours ago, Mihanicos said:

Assuming you are using the correct type and viscosity of oil, and depending on your driving style, daily trip lengths, ambient temperature, terrain of driving and load, some oil will be consumed by any healthy engine.

Make sure you are using the correct ACEA C rating of engine oil. This rating depends on the High Temperature Shear Viscosity of the oil. Using the wrong HTSV oil will cause engine damage.  See ACEA oil specifications.

Check the compression of each cylinder. Worn piston rings and an engine that overheated will cause oil consumption.

Worn valve seals will also cause engine oil consumption. It is possible to change them without removing the cylinder head.

Inspect the spark plugs. A healthy engine will have the electrode porcelain colour light chestnut brown, indicating a stoichiometric combustion. An oily and sooty electrode indicates excessive oil consumption either from the piston rings or the valve seals.

Some engines other than Toyota and Lexus are designed to burn oil  about 1.5 litres per 1000 miles for normal driving conditions. The reason for this is to improve fuel economy at the expense of blocking the catalytic converters.

Chris.

I’m using the correct oil and I’ve done a lot of research and read many forums.
I’m just getting to a point of I either get rid of the car or I fix the problem.

do you know what the price would be for either the seals or the pistons?

ive just bought a new exhaust which cost £900 so I’m reluctant to get rid but I’m not prepared to spend thousands especially seen I don’t have that kind of money.

[AFlex]

Hi @Mrt23

I have a 2007 Lexus IS250 (slightly older than yours) and I have a similar oil burning problem (sometimes as bad as 1.5l per 1000 miles). It only seemed to get bad over the last 3 years or so. In that time, I've moved to the city and so my driving style has changed considerably (lots of very short trips).

I've spent quite a lot of time researching why on earth it is burning oil so ferociously and the most plausible answer seems to be that it's a common problem with modern Toyota engines since they use weak piston rings that dont have sufficient force to seal themselves against the cylinder walls. This improves the fuel efficiency of these engines since they create less friction against the cylinder walls, but as @Mihanicos explained, this is at the expense of your engine burning more oil and your catalytic converter (and your O2 sensors) are likely to fail sooner due to all the burned oil which is passing through the exhaust. The modern weak piston rings are very susceptible to getting gunked up from your dirty oil.

What happens in the early stages is that the piston rings get all gunked up with dirt and carbon and they cease to give a tight fit against the cylinder walls. Oil can then get past the piston rings into the cylinders and is burned during the combustion process. If your problem progresses to the later stages, damage is unfortunately caused to the cylinder walls and this will not be possible to repair easily.

How can you fix this?
You can try to clean some of the dirt off using a cleaner like Marvel Mystery Oil (MMO) and see if this helps. I've just added MMO with my last oil change so will see how much this improves things.

You will probably also benefit from cleaning the catalytic converter with something like Cataclean. I've just done mine and I can tell the engine is immediately more responsive.

From now on, I will be doing oil changes twice per year (for me this means a change very 2,000 miles). I've now got all the tools to change the oil myself and it really is a very easy job and, if you buy oil in bulk, it only costs about £20-30 per change.

This guy explains the problem with our engines quite well:

 

Here's a video on how to use Marvel Mystery Oil

 

[AFlex]

Forgot to add, I am at very similar mileage, 100k

[Shayo Elizabeth Adebayo]

Thanks alot Aflex for ur detailed explanation, it's quite helpful. I just got my is250, and though i didn't do my findings to be abreast of the cabon build up issue, your post has really helped in dealing with it.