MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Flushing Oil

Hi all...

I have been following the oil filter magnet thread with interest.

While we are having oily thoughts, what do you think of flushing oils ?.. I have heard people say they are great, and I have heard people say that they are risky because you don't get all of it out when draining, and the remaining flushing oil is detrimental.

Comments please... Don
Don

Don,
I must be honest and say I agree with the second school of thought.

If the oil and filters are changed as and when they should be then it seems to me to be a waste of money.

I have heard the horror stories too but they are regarding damage done to seals more than the flushing substance left behind.

Interesting question though.

Cheers, Pete.
Peter Thomas

I only use the same oil that I run with to flush. If you have an oil cooler it wont drain with changing.

Keep that top down, it's not winter yet.
Ken Knize

Don. Check the archives. I started a similar thread several years ago and there were some very knowledgable people who contributed to it. Biggest problem with flushing oils is if they break loose a large particle that stops up an oil passage. However, I have never seen this happen myself. There are a number of "home brew" systems that claim to do the same thing, but allow you to drive while doing so. (Flushing oil is used with the engine idling and the makers claim you should not drive witht eh flushing oil in the crankcase.) Some claim that a quart of ATF added to the oil will help clean the system because ATF is SAE 10 oil with a lot of cleaners added. Others claim that a quart of Marvel's Mystery Oil added to the engine oil, then changed after 500 miles will result in a cleaner engine. People who have tried both seem to feel that they have helped. Today, I use Castrol 20-50, change the oil and filter every 3K miles and the engines I disassemble for rebuilds are very clean. Especially as compared to the ones I used to tear apart back in the late 60's. Back then, flushing oil was very useful. Today, I do not see the build up of sludge in the sump that I used to see. Hence, regular oil changes are all that I believe are needed. Les
Les Bengtson

When I service customers cars, I drain the old oil out of the engine, swap the old filter for a temporary one kept for the purpose, fill the engine with cheap 20/50 oil (£1 per litre, run the engine till hot and then drain the oil again (this oil can be reused a couple of times for this purpose), change the filter for a new one and refill with fresh good quality 20/50 oil (Duckhams or Castrol).

This ensures that the dirty old oil in the pipes and cooler are diluted to 10% on the first change and then to 1% or so on the second change.

On really bad old engines I add a pint of diesel to the old oil before running the engine to get the oil really hot - this dissolves any gum in the system but is unlikely to loosen any carbon encrustations - most of the engine flushes you can buy are deisel based.
Chris at Octarine Services

Chris,
With all due respect, I don't believe that many people would want oil and filter that have been used, even once, to flush the gunge from someone elses lump to to be re-used on their engines. I would be appalled if I discovered that my mechanic were doing such to my car and would do business elsewhere.
Brian McFarland

Don;
Several years ago a customer brought in a Chevy pickup for me to inspect. He had just purchased the truck and wanted my opinion as to its condition. I told him it appeared to be in good shape and that all it needed was a service. His response was that whenever he bought a new vechile he always used a flushing compound in the crankcase. Against my advice, he ran the engine with the flushing compound and lost all oil pressure. I dropped the pan and found the oil pump screen completly clogged. After replacing the oil pump the enging lasted five hundred miles then snapped the crank in half. In the process it also broke the block in two. I would advise against it. Ray
Ray

Brian --

I don't believe you understand the purpose and reasoning behind Chris's oil changing procedure.

Of courese that is just another opinion.
glg

<<<Brian --

I don't believe you understand the purpose and reasoning behind Chris's oil changing procedure.
>>>


GLG,
Again, with all respect, what is there to understand? I deliver my car to a garage for a service. My engine is full of swarf from some mechanical demon. My oil is drained and then flushing oil is added whilst installing the filter set aside for this purpose. The flushing oil is drained and retained along with the filter that has metal shavings or other rubbish suspended in it. Your year-old, expensively restored car comes in behind it and has the filth from my engine go into yours as flushing oil. Would that make you happy? If you feel that I am still in the dark, please shed some light.
Brian McFarland

Brian,

You are entitled to your view - but to suggest that I would miss the fact that a sump is spewing metal swarf and would then just rinse it out and retain the oil to reuse insults my intelligence.

Normally the "flushing" oil comes out quite clear and free of debris, if it was otherwise I would not reuse it other than in the workshop heater.

After 3 uses the oil is still over 70% clean and the oil in your sump is 8-9% cleaner than if the old oil had simply been drained and replaced.

Oh - and the new filter hasn't been hit with a shot of neat old oil straight out of the cooler and lines.

Regardless of the sensibilities of customers, most of the people on this bulletin board are "hands on" and probably change their own oil, so use and reuse of a can of cheap oil for this purpose is likely to be acceptable.

The tip is offered for what it is worth - no more, no less,
Chris at Octarine Services

Brian,

Thanks for a civil response. I have no light to shed, as stumbling in the darkness of stupidity is the only thing I know for sure as I meander through this thing called life.

Personally, that flushing procedure is something I would never consider as a routine maintenence. That is because when my engine was rebuilt, it went through the hot tank process any sludge/gooo was removed.

It would appear to be a better alternative to follow Chris's procedure than using any over the counter oil flushing chemicals. The main "good point" is removing any latent oil from cooler and plumbing.

Too, i was under the impression that he uses a recylced new oil during intermediate flush. (not some crappy oil with 170,000 miles --- ) I am guessing here, but I took it as him using a un-road-run oil just to get the oil system a tad bit cleaner.

Perhaps Chris will expound on this. In the end, all of the maintence schedules we keep both in material, style and frquency is a personal thing -- all with the intent and purpose of keeping the breed alive.

Saftey fast! glg
glg

GLG,
I,too, would shun flushing as a routine procedure for the same reason and I change the oil in all of my vehicles religiously.

I did not mean to offend Chris. He is one of the most knowledgeable and helpful individuals on this bulletin board. My illustaration was meant as a worst case scenario, although I stand by the fact that I don't want my dishes washed with someone elses dirty dishwater.
Brian
Brian McFarland

Brian,

This may be a point of misunderstanding

I drain the old oil out of the engine, swap the old filter for a temporary one kept for the purpose, fill the engine with cheap 20/50 oil (£1 per litre, run the engine till hot and then drain the oil again (this oil can be reused a couple of times for this purpose), change the filter for a new one and refill with fresh good quality 20/50 oil (Duckhams or Castrol).


He's using a new, clean, never run oil and filter. And it's only used a couple of times, before he replaces the flush oil and filter.

So, it's not used oil or filtet from some other customers cars. The oil will notbe black from extended use.

Since I've made a few guesses here, one more is that flushing oil and filter gets replaced after six to ten cars, then replaces with NEW flushing oil and filter,

Make better sense to you?
glg

glg,

you are spot on - except that the oil and filter gets changed for brand new after 2 or 3 cars.
Chris at Octarine Services

Well, That was fun and easy!

Keep what you got going and refurbish what one life time allows!

Cheers Mates!
glg

<<<glg,

you are spot on - except that the oil and filter gets changed for brand new after 2 or 3 cars.>>>


GLG,
This is what I have been trying to communicate to you. He flushes two or three engines with the same oil and filter. Am I the only one who has a problem with this? My God, I feel like I'm in a Fellini movie.
Brian

Brian McFarland

I never bother using flushing oil on the 4-cylinder but frequently do in the V8, where the oil stays clean-looking on the dipstick throughout its use (3k). Without flushing the V8 oil comes out relatively clean, with putting clear flushing oil in it comes out black as night. Either something is undergoing a chemical change to the opacity or the flushing oil is removing something more than comes out with the oil. At a recent top-end overhaul the inside of the crankcase a light gold colour, which according to RPI equates to 'low mileage' even though it has done 80-100k since the last rebuild. I think changing the oil then changing it again is more to do with removing the old oil from the oil cooler and hoses than cleaning the rest of the engine.
Paul Hunt

Paul,

I do the same to my V8 - I think the flushing oil is dissolving the brown/black gummy substance that adheres to the ally castings. The ordinary oil leaves this undisturbed.

And yes - double changing just removes more of the old oil rather than cleaning anything.

Brian,

What's a Fellini movie????
Chris at Octarine Services

I would totally applaud Chris's approach, and I wish more garages would do this instead of using Forte and charging rediculous amounts for it.

I would agree with Les that a regular maintenance schedule with frequent oil changes would minimise the need for flushing, but on cheaper oils depositing will be an issue and , especially after any 'open heart' maintenance, the engine should be flushed as described by Chris.

In our training classes for industrial maintenance, we recommend as best practices that at every 2nd oil change on a gearbox or bearing in the plant that the oil is flushed. The best flushing oil is the oil that is regularly used in the machine. In the case of splash lubricated, non-circulating systems, we would recommend the use of filter cart and pump to turn the oil over six or seven times through the filter (do the maths based on flow rate and sump volume). We would also advise the 'flushing' oil can be re-used a number of times to avoid wastage, and the storage container clearly marked as 'flushing' oil. The number of safe times will depend on the percentage residual. The higher the level of the residual oil, the fewer the number of times it should be re-used because of a greater dilution. We recommend this flushing procedure to clients doing a change from one supplier to another to minimise additive interference between oils.

In engines, anything from 5% to as much as 20% or more can be left residual, especially if the engine was not warmed properly prior to draining. Research has shown that just 10% of the old oil left will very quickly damage the new oil's additives. Its analogous to a contagious sick person entering a room. he doesn't get better, but a good few of the healthy folk will sucumb!
If you buy a car with a questionable service history, this approach is good practice, and one can drive the car for a few miles to get the oil properly hot and circulating before again draining and refilling with fresh. Always change the filter with the oil, unless keeping it for further flushing.

As to the filters, well modern engine filters are improving, but as my employer, James Fitch, has said, the ability of dirt to enter a system is greatly underestimated, and the ability of the system filter to remove that dirt is greatly over-estimated! On an engine that dirt enters in the new oil, the air intakes and the fuel supply, as well as in the wear material produced. Unless there is catastrophic wear taking place, the normal wear material is often less than 10microns in size.
In the first instance, a filtered oil dispensed into the engine for filling would be a big advantage. However, Formula one teams usually use a high performance filter for circulating and flushing the oils on their systems. Remember that some of the component clearances are as little as 10microns or less, and may even be boundary contact. The human eye can see contrasting colour particulate down to 40microns. So the enemy in your engine is dirt and one of the most overlooked areas of wear protection. New oil is not clean oil. Modern barrier filters will operate down to 5micron with a 1 in 1000 slip through at that size. Older paper filters will have a 40-50 micron media with a 1 in 10 pass through or beta ratio. Industrial hydraulic filters are highly regulated by ISO, yet automotive filters carry no performance guarantees! Paper elements are often inconsistent in pore size rating and are susceptible to tearing when wetted or subject to pressure surges. For normal flushing as described by Chris the normal filter should be sufficient for at least 4 to 5 flushes without shedding dirt. However, a high performance industrial filter on a kidney loop or offline circuit would provide exceptional life for at six months without fear of it shedding any dirt trapped.

All food for thought!
Martin

Hi all...

I had the feeling that this would be a little controvertial.

My usual practice has been to change the oil and filter at regular intervals and occasionally give the engine a 'birthday' by flushing it with cheapish ordinary oil.

I never start the engine for a short run, and am considering some sort of electrical heater to pre-heat the block.

Thanks to everyone who replied.

Don
Don

Although Martin's post back's up Chris's practice especially with an oil cooler.

I would be concerned about unknown used oil being used as opposed to new or oil used for flushing only on my car, even if it may be good commercial practice.
Given a choice as a customer I would prefer to have new oil used at a small extra cost, even if it may be over the top.

Would flushing be necessary using Synthetic and a high performance filter?

Paul
Paul

In that case, Paul, I promise to only ever use a brand new, unopened container of oil to flush out your engine when you bring it over for a service 8-).......... and I won't charge you extra for it either.

The issue remains whatever oil type or filter you use - as the old oil ages in the engine, its additives get used up and the oil carries contaminates that the filter does not remove. The whole point of flushing with fresh oil is to dilute any remaining old oil in the system and minimise the final level of contamination of the new oil that remains in the engine when the job is done.
Chris at Octarine Services

Paul
I think it comes down to this:
If you do this at home, then you would know what oil you are using at each service. If you used Chris regularly, you would also know what you are getting. Presumably Chris doesn't shop around all the time and keeps a stock of a preferred brand of oil?

However, unlike Chris running a business using his flushing oil every week for a 3 or 4 cars, if done at home, I would use the flushing oil for no more than a year (say 2-3 oil changes). The reason being that stood in your garage at home, the process of oxidation will start to degrade the oil even though it has not been used in anger!
HTH
Martin

Chris,

Good answer, and next time in Essex I will pop in for oil change, especially if I'm using Synthetic, although I will be happy to buy you a pint of Speckled Hen in exchange for your excellant advice.

Just to make sure
As Martin mentioned above "I would totally applaud Chris's approach, and I wish more garages would do this instead of using Forte and charging rediculous amounts for it"

Paul
Paul

This thread was discussed between 05/10/2003 and 11/10/2003

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.