Best oil leak stopper

[Aerodynamik]

Hi all

For some time now my 1.6 2017 Peugeot 3008 (90k miles) has been burning oil. Never signs any leaks and gets through MOT on emissions but uses about 1 ltr every couple of months.

Is there a best oil additive out there to possibly stop the leak?

TIA

Edited by Aerodynamik on Saturday 19th September 22:49

[Derry Rhumba]

I used Liqui Moly Oil Saver on a valve cover leak on my 2007 E90; just to buy me a bit of time as my hands are too full to change the gasket right now.

It does seem to have worked, although a couple of things to note; you do have to drive a good few hundred miles before the additive takes effect, also my leak seemed pretty small, nothing like the amount your losing.

I'm not really a user of these additives normally, first time i've used one in fact; so maybe someone who has more experience of them can be more help.

[Richard-D]

You don't have an oil leak, your engine is burning oil. These are two completely different problems. Your issue is most likely caused by worn cylinders/piston rings and/or ineffective oil control rings. Someone who's never worked on an engine will probably tell you it's your valve stem seals. Usually people say this because they've heard other people say it.

To determine if it's excessive you really need to relate it to miles, not time. If you're doing 5k miles in those two months it's considered acceptable by many manufacturers. If you're doing 200 miles then that's a very different situation.

Edited by Richard-D on Sunday 20th September 00:09

[oakdale]

Aerodynamik said:

Hi all

For some time now my 1.6 2017 Peugeot 3008 (90k miles) has been burning oil. Never signs any leaks and gets through MOT on emissions but uses about 1 ltr every couple of months.

Is there a best oil additive out there to possibly stop the leak?

TIA

Edited by Aerodynamik on Saturday 19th September 22:49

Wynn's supercharge.

[Derry Rhumba]

Richard-D said:

You don't have an oil leak, your engine is burning oil. These are two completely different problems. Your issue is most likely caused by worn cylinders/piston rings and/or ineffective oil control rings. Someone who's never worked on an engine will probably tell you it's your valve stem seals. Usually people say this because they've heard other people say it.

To determine if it's excessive you really need to relate it to miles, not time. If you're doing 5k miles in those two months it's considered acceptable by many manufacturers. If you're doing 200 miles then that's a very different situation.

Edited by Richard-D on Sunday 20th September 00:09

I did consider pointing this out, (the burning oil bit), but then thought if there is a small leak finding its way onto the undertray and not noticable then it might be both.

But yeah, no additive is going to fix a loss (whatever the cause) of a "litre every couple of months".

[E-bmw]

Richard-D said:

You don't have an oil leak, your engine is burning oil. These are two completely different problems. Your issue is most likely caused by worn cylinders/piston rings and/or ineffective oil control rings.

To determine if it's excessive you really need to relate it to miles, not time. If you're doing 5k miles in those two months it's considered acceptable by many manufacturers. If you're doing 200 miles then that's a very different situation.

^^^^Wot 'e said.

Good advice indeed.

If there is a time/condition that causes any oil burning smoke to be visible then feel free to tell us as it CAN help to narrow down the area of the issue.

[_Rodders_]

My guess would be gummed up oil control rings unless you've gone over and above on the oil changes.

Not a huge amount you can do really. If the consumption is less than 1 litre per 1000 miles I'd be tempted to leave it or sell while it can still pass emissions.

[Richard-D]

I don't know about this engine specifically but some engines have a habit of getting their oil control rings stuck. I had a 1.8 Duratec that did this which I ended up doing a partial rebuild in situ. It's a bit awkward but you can do this with most cars by just removing the sump and cylinder head.

One check you can do easily and quickly is to ensure the PCV valve isn't stuck (which will vacuum out the oil from the crankcase at idle if so). With the engine idling remove the oil filler cap. There should be a small amount of air blowing out. If there's a vacuum them your PCV valve is at fault (easy and cheap). Put your hand flat over the filler neck and you'll feel it sucking if that's the case.

[Derry Rhumba]

^^^^Or excessive blowing onto the palm of your hand. Very slight suction/blow normal.

[Richard-D]

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

[Derry Rhumba]

Richard-D said:

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

Happy to be corrected here, (every day is a school day)

But I had thought a stuck closed pcv valve caused excessive blowback, (as does bore/ring wear as you said), and a stuck open pcv valve causes excessive suction at the oil filler?

Will feel pretty daft if about to be educated otherwise as I've used this rule of thumb for ages!

[Castrol for a knave]

Richard-D said:

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

Will a failed pcv valve put oil vapour into the air filter, as part of the blow back?

I know on some cars it is a tell, depends on the intake routing I guess

[Richard-D]

Derry Rhumba said:

Richard-D said:

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

Happy to be corrected here, (every day is a school day)

But I had thought a stuck closed pcv valve caused excessive blowback, (as does bore/ring wear as you said), and a stuck open pcv valve causes excessive suction at the oil filler?

Will feel pretty daft if about to be educated otherwise as I've used this rule of thumb for ages!

The way the system works is slightly counter-intuitive because of how plenum vacuum works. Essentially you use plenum vacuum to scavenge blowby gasses from the crankcase (for a couple of reasons but mainly to keep engine oil clean). Higher in the rev range there is less vacuum in the plenum chamber, at this point the PCV is open to allow blowby gasses to be pulled into the intake and burnt. At idle vacuum is much higher (because your intake is pulling against a closed throttle plate) and if the PCV were open you would pull too much vacuum in the crankcase (sucking oil in the process). For this reason at idle your PCV valve is fully closed (pulled closed by the vacuum).

There are some PCV systems that work without a PCV valve. The Rover K-Series is like this, it relies on a restrictor to limit the airflow into the intake from the crankcase. Most normally aspirated engines have a PCV valve that works how I've described above though.

[Richard-D]

Castrol for a knave said:

Richard-D said:

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

Will a failed pcv valve put oil vapour into the air filter, as part of the blow back?

I know on some cars it is a tell, depends on the intake routing I guess

A PCV valve can generally fail one of two ways (sticking open or sticking shut). If it sticks open then it will still be open when the plenum vacuum is high (at idle), hoovering oil into the intake from the crankcase. If it sticks shut it can cause excessive pressure in the crankcase. Generally excessive pressure will make its way out via another route. By far the most common way for it to fail is to stick open.

I answered in such a long winded way because the system intentionally puts oil vapour back into the intake, when it's working properly not just when it's failed. The difference is when it does it. Typically it's after the air filter though (not nit picking here, only mentioned as you said filter in your question).

[Wacky Racer]

Just buy some decent oil in bulk and keep topping it up every two weeks if it's burning oil.

Not ideal, but probably the cheapest alternative to a rebuild.

Obviously. if there's an oil leak, get that sorted.

[Castrol for a knave]

Richard-D said:

Castrol for a knave said:

Richard-D said:

Just to clarify the above, excessive blowing onto your hand is not caused by a failed PCV valve. That is a sign of excessive bore/ring wear. Appreciate the above poster will know this but the OP may not.

Will a failed pcv valve put oil vapour into the air filter, as part of the blow back?

I know on some cars it is a tell, depends on the intake routing I guess

A PCV valve can generally fail one of two ways (sticking open or sticking shut). If it sticks open then it will still be open when the plenum vacuum is high (at idle), hoovering oil into the intake from the crankcase. If it sticks shut it can cause excessive pressure in the crankcase. Generally excessive pressure will make its way out via another route. By far the most common way for it to fail is to stick open.

I answered in such a long winded way because the system intentionally puts oil vapour back into the intake, when it's working properly not just when it's failed. The difference is when it does it. Typically it's after the air filter though (not nit picking here, only mentioned as you said filter in your question).

Appreciate the detailed answer. I had heard that when the pcv valve fails, it can coat the filter due to it being the least pressurised airway

Your explanation makes sense

Cheers

[Derry Rhumba]

Richard-D said:

The way the system works is slightly counter-intuitive because of how plenum vacuum works. Essentially you use plenum vacuum to scavenge blowby gasses from the crankcase (for a couple of reasons but mainly to keep engine oil clean). Higher in the rev range there is less vacuum in the plenum chamber, at this point the PCV is open to allow blowby gasses to be pulled into the intake and burnt. At idle vacuum is much higher (because your intake is pulling against a closed throttle plate) and if the PCV were open you would pull too much vacuum in the crankcase (sucking oil in the process). For this reason at idle your PCV valve is fully closed (pulled closed by the vacuum).

There are some PCV systems that work without a PCV valve. The Rover K-Series is like this, it relies on a restrictor to limit the airflow into the intake from the crankcase. Most normally aspirated engines have a PCV valve that works how I've described above though.

Richard, thanks very much for taking the time to explain it so fully. Very generous of you and much appreciated.

It's over 40 years since I finished my engineering apprenticeship, and a long time since my day job was "on the tools".

I'm not too bad at keeping my 3 ancient cars on the road via servicing and straightforward repairs, but Im a million miles away from being a motor mechanic so genuinely pleased to get this type of gen from those who know better.

Thanks again

[aterribleusername]

Richard-D said:

You don't have an oil leak, your engine is burning oil. These are two completely different problems. Your issue is most likely caused by worn cylinders/piston rings and/or ineffective oil control rings. Someone who's never worked on an engine will probably tell you it's your valve stem seals. Usually people say this because they've heard other people say it.

To determine if it's excessive you really need to relate it to miles, not time. If you're doing 5k miles in those two months it's considered acceptable by many manufacturers. If you're doing 200 miles then that's a very different situation.

Edited by Richard-D on Sunday 20th September 00:09

Absolutely this.

My car is on 250k and over the last 20-30k it has started to use a bit of oil between oil changes. I've had it from new and it never used any oil in all that time despite it being known to use a bit (a litre every 10k is not unheard of) so it turns out I've had a good one as it's only using 2-300ml between changes. I used to fill it up to halfway up the dipstick but I've switched to going to the top mark and it is just below halfway at each change now, no need to top it up between them but it does mean I have to buy an extra litre for two oil changes as it has a 2.4 litre sump and 2.5 litres per change brought it bang on the middle of the disptick. As the oil comes in 5 litre bottles it was ideal. No sign of any leaks and no sign of smoke either so if you've got the same scenario I'd just keep on topping it up and monitoring the oil usage.