Engine Oil Flush - What are your thoughts?

testrider

testrider

Active Member
I've got to do an oil change on my Volvo this week that's done 162000 miles and when I had the cam cover off recently to replace the valve stem seals I noticed it was a bit gunged up at one end of the engine. So, I was wondering about pouring a can of engine flush in this time to give it a good clean out.

I can see both sides to the argument for and against using it:-

1) cleaning all the gunge out of the engine properly before you put fresh oil in should make it last longer and reduce wear.

2) cleaning all the gunge out of the engine properly will leave the piston rings and oil seals prone leaking and will dislodge huge chunks of crap that will block oil ways.

So what do the rest of you think?
 
I think at that mileage if it's going OK , leave it alone
If you want to flush the engine , fill it with cheap oil afterwards and drain at 1000miles to get all the loosened crap out
 
I have always used a flush, I used to use flushing oil but it's almost impossible to find now. I was lucky and picked up a big box of tins of flush for about 20p a tin (they sell it in Halfords for £5 a tin). I've never had any problems...

However, I agree with Dave's suggestion of doing a couple of short changes, one recomendation is to use a Diesel engine oil (not diesel fuel !!), drop your old oil and refil with the diesel oil, use this for a few hundred miles, then do the normal oil and filter change back to your normal oil. The theory is that diesel engine oils have a much higher detergent content and will help to remove the crud, plus you're using a normal oil rather than thinning the old oil with a tin of flush. If you can find a really cheap diesel oil, it won't cost much more than a tin of flush either.
 
webmaster said:
The theory is that diesel engine oils have a much higher detergent content
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Having done significant (PHD level) research into engine oils, I have been told by more than one manufacturer that 'Diesel' oils are exactly the same formulation as their petrol oils.

In fact, one manufacturer who sells in the UK marketing their products under two names advertises the same product under one name as being a 'Diesel' oil and under the other name as being for petrol & diesel engines. The idea being that owners of Diesel cars feel happier buying something marked 'Diesel'. :)

Having said that, I'd agree that several oil changes done more regularly than recommended may be better than a flushing oil/substance.
 
Thanks for your input guys, I reckon I'm going to just do a normal oil change and leave the engine flush this time. I think I might make some time at the next service to drop the sump and clean it out with elbow grease, don't really have the time now.
 
My P6 blow it's bigends within a couple of weeks of an oil change using Halfords oil for classics that is suposed to have 'cleaning' agents. Very lightly they were due to go but I feel this 'cleaning' may have hastened thier departure. I now use standard mineral oil from the local independant car parts place that does not contain any 'extras'.
 
richarduk said:
My P6 blow it's bigends within a couple of weeks of an oil change using Halfords oil for classics that is suposed to have 'cleaning' agents. Very lightly they were due to go but I feel this 'cleaning' may have hastened thier departure. I now use standard mineral oil from the local independant car parts place that does not contain any 'extras'.
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I've used Halford's Classic oil for the last half a dozen or so oil changes (every 3K miles) and have had no problems with it.

Dave
 
Dave3066 said:
richarduk said:
My P6 blow it's bigends within a couple of weeks of an oil change using Halfords oil for classics that is suposed to have 'cleaning' agents. Very lightly they were due to go but I feel this 'cleaning' may have hastened thier departure. I now use standard mineral oil from the local independant car parts place that does not contain any 'extras'.
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I've used Halford's Classic oil for the last half a dozen or so oil changes (every 3K miles) and have had no problems with it.

Dave
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Unfortunate coincidence in my case, I did wonder if the old oil had some of that 'make it like treacle' additive in it and putting good oil in was the straw that broke the camels back.
 
Dave3066 said:
richarduk said:
My P6 blow it's bigends within a couple of weeks of an oil change using Halfords oil for classics that is suposed to have 'cleaning' agents. Very lightly they were due to go but I feel this 'cleaning' may have hastened thier departure. I now use standard mineral oil from the local independant car parts place that does not contain any 'extras'.
Click to expand...

I've used Halford's Classic oil for the last half a dozen or so oil changes (every 3K miles) and have had no problems with it.

Dave
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Halfords green stuff is basically the same as Duckhams, highly recommended.
 
Previously used Wynns Engine Flush pre oil change with no ill effects. Think its best to take car for short run first to settle oil temperature and pressure . When back home, add flush then let it tick over for about 10 minutes or so whilst stationary, never drive it with flush in which would load engine too much. When draining, I'll usually go and do something else for a fair while ,so when I come back its hand maximum drain possible. Providing your engine is in good health in the first place I can't see it being detrimental to the long term engine life.

Another method is a "double oil-change" although rather more expensive. In Ferrari Workshop Manuals" , they recommend this when changing grades of oil in the engine. Drain original oil, then replace sump plug. Fill engine with new grade, run whilst car stationary for 10-20 minutes , then drain again. Replace sump plug , refill again with another quantity of new grade with new filter. The first refill supposedly conditions engine for new grade, and when you immediately drop it , makes sure any residue of oil grade comes out too. You could apply this method whilst keeping to same grade, to act as a secondary flush without using 3rd party solutions in the oil, but , like I say , a little more expensive.
 
My instinct is that flushing oil is a good plan as a regular routine, say every two oil changes. I'm much less sure about its advisability in a very old/very gummed up/very neglected engine. I'm with the camp that fears major particles being dislodged and getting stuck in unfortunate places. If you are already staring at a major rebuild, it could be worth a punt to see if some more miles can be squeezed from what you have now, provided you understand the risk of precipitating the rebuild now instead of in 3 months time!

Chris
 
Another thing to remember , with modern cars , very often in later life their oil changes don't get up to date, and sometimes they have problems making it through emissions come MOT time, the remedy being a thorough oil flush and change to cure the situation.
 
When you start with a clean new/rebuilt engine, regular oil changes should be enough to keep it free from sludge. I have covered almost 40K miles since i fitted the rebuilt engine and i change the oil every 3K miles and the filter every second change. Well, the engine is still clean inside. I don't see the point in using any flushing products.

On the other hand, as Chris said before, if you start with a very neglected engine, with plenty of sludge and carbon build up, you wouldn't want all this nasty stuff to become dislodged and start to circulate within your engine, and of course its bearings even for 10 minutes.
 
Thanks for the contributions. I wondered if this would be a very short thread with just a couple of 'don't bothers' but there's more reasoned debate than that whic is good.

Chris, I've had the car for a while, putting almost 40000 miles on the clock myself, and I have no plans for a major engine rebuild. I only replaced the valve stem seals as the were leaking and I didn't have to completely strip the engine to do it.

What it did highlight whilst poking around inside though was that the front of the engine was very clean and shiney with just a slight golden glaze on the bare metal surfaces which became gradually darker moving to black towards the back of the engine.

Clearly Volvo need to work on their oil circulation as it's a common feature for these five cylinder blocks and I thought the engine flush might remedy that, but I shan't bother now.

Demetris made an interesting comment about keeping his rebuilt engine clean with 3k mile oil changes and I hope to be able to do the same with my V8 too. However, all the oil manufacturers claim to be able to do this, but surely the engine will begin to sludge up at some point or can you keep it clean indefinitely?
 
testrider said:
Demetris made an interesting comment about keeping his rebuilt engine clean with 3k mile oil changes and I hope to be able to do the same with my V8 too. However, all the oil manufacturers claim to be able to do this, but surely the engine will begin to sludge up at some point or can you keep it clean indefinitely?
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I guess it really depends on how often you change the oil. I cannot really comment on suggestions for modern engines and 20K oil change intervals, but in our situation where piston blow by is something we have to live with, frequent changes are vital.
To put it simply, if you have a healthy engine and change the oil before it gets dirty, then you wouldn't have to worry about sludge. However, as the engine gets more and more worn by use, it will tend to get its oil dirty sooner and sooner. At one point it will not be practically possible to change the oil before it gets sooty black, and therefore you cannot avoid sludge. Frequent oil changes will probably move that point further away, but it won't stay like this for ever!

There are not many things that last indefinitely! :roll:
 
If you have a look at http://www.carbibles.com/engineoil_bible.html
They suggest that sludge is at least partly down to the oil breaking down by heat etc, and that more frequent changes will effectively prevent it ever happening.

Another thing I was always told was that once oil is in the engine, mixed with the remains of the previous oil, and being subjected to engine running, it will break down over time, regardless of mileage driven. I heard of people leaving the same oil in their classic for years because they only do 500-1000 miles a year, so for a 6k oil change they can get 6-12 years out of the oil !, It's worth changing it every 6 months (possibly 12 at a push) regardless of mileage.

I think the most important rule here is, as far as I know I've never heard of an engine sufferring or failing because of too-frequent oil changes, so just change the oil (and filter if you can) as often as you feel you can stand.
 
These modern diesels that can do 20K miles between oil changes are only to produce an impression of reduced servicing costs.And have you seen how small the oil filters are these days ?
Now I own my former company car it's getting clean oil and filter every 10k
 
Diesel fuel is a light oil, And a local mechanic assures me that draining the oil from my 3500v8 AND leaving the oil fillter in place and replacing the sump plug THEN Fill the engine with two gallons of diesel and remove the HT lead turn engine over two or three times and leave for a few hours repeat the procedure for three to four times and leave overnight, drain out diesel and and re fill with a gallon of diesel turn over engine a few time and drain blow down engine with a air line oil filler + dipstick tube,and leave to drain. fill engine with recommended oil fit new primed oil filter and turnover engine until oil light goes out reconnect HT lead. Apparently diesel fuel destroys old oil deposits and turns them into liquid sludge. the diesel being light oil protects the engine during the cleaning process? what are your thoughts on this! :roll:
 
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