Flushing oil in a diesel engine
Discussion
Slight self-plug, I filmed my last PD change and put it on the Toob:
YouTube
I wouldn't put anything but the correct spec oil in a PD; flushing oil certainly isn't. If you're concerned do a change then do another change a few thousand later, but I really wouldn't. Just do a change now with an OE filter and correct oil then stay on top of the schedule.
YouTube
I wouldn't put anything but the correct spec oil in a PD; flushing oil certainly isn't. If you're concerned do a change then do another change a few thousand later, but I really wouldn't. Just do a change now with an OE filter and correct oil then stay on top of the schedule.
Diesel oil is pretty high detergent anyway. It has to be to keep as much of the nasty black grot in suspension as possible. I'd just stick to a synthetic oil of the recommended grade, change it regularly and leave it at that.
As an aside do you know why engines wear out in the first place? It isn't the oil quality although of course better oil helps. However commercial diesels have routinely lasted for over 500,000 miles (or 20,000 hours run time before rebuild) going back well before synthetic oils were ever invented. It's actually the filtration, or lack of it, that causes wear. 99% of the wear that takes place in any engine is due to contaminants inhaled through the induction system and the resulting wear particles not getting filtered out quickly enough or finely enough by the oil system.
Commercial diesels (ships, trucks, power generation engines etc) have much higher quality induction and oil filtration systems than cars. Partly because there is more space to fit them and partly because the engine cost and vehicle lifespan makes it worthwhile. Apart from taxis cars don't generally run for long enough to make it worthwhile fitting 500,000 mile spec filtration systems. If they had them though there's no doubt they'd last for much longer than is normally possible.
With the right filtration you could run modern engines on the oils available 30 or 40 years ago and they'd be perfectly happy until the chassis had rotted away long before the engine ever broke down.
As an aside do you know why engines wear out in the first place? It isn't the oil quality although of course better oil helps. However commercial diesels have routinely lasted for over 500,000 miles (or 20,000 hours run time before rebuild) going back well before synthetic oils were ever invented. It's actually the filtration, or lack of it, that causes wear. 99% of the wear that takes place in any engine is due to contaminants inhaled through the induction system and the resulting wear particles not getting filtered out quickly enough or finely enough by the oil system.
Commercial diesels (ships, trucks, power generation engines etc) have much higher quality induction and oil filtration systems than cars. Partly because there is more space to fit them and partly because the engine cost and vehicle lifespan makes it worthwhile. Apart from taxis cars don't generally run for long enough to make it worthwhile fitting 500,000 mile spec filtration systems. If they had them though there's no doubt they'd last for much longer than is normally possible.
With the right filtration you could run modern engines on the oils available 30 or 40 years ago and they'd be perfectly happy until the chassis had rotted away long before the engine ever broke down.
Pumaracing said:
It's actually the filtration, or lack of it, that causes wear. 99% of the wear that takes place in any engine is due to contaminants inhaled through the induction system and the resulting wear particles not getting filtered out quickly enough or finely enough by the oil system.
Is that fact or opinion? Never knew that. (not getting at you btw, just interested)
The thing with such high filtration is right in line with what FoolOnTheHill said.
Commercial diesels run at much lower RPM than street car diesels. Trucks, buses, generators very rarely spin past 1500-2000rpm while my Ford Focus generally sees quite a bit of action past 3500.
The filter's resistivity to the oil's flow is what saps power from the engine, and it rises with the square of engine speed. To prevent the huge loss of power that would occur at high RPM, street car diesels have a bypass valve that activates past 2500 or so rpm and bypasses the filter. During that time the oil in the engine is basically unfiltered.
Given that commercial diesel engines run at much lower engine speeds, the filter's resistance to flow is much less of an issue and so it never need be bypassed, and thus the oil stays cleaner.
Or so i was explained.
Commercial diesels run at much lower RPM than street car diesels. Trucks, buses, generators very rarely spin past 1500-2000rpm while my Ford Focus generally sees quite a bit of action past 3500.
The filter's resistivity to the oil's flow is what saps power from the engine, and it rises with the square of engine speed. To prevent the huge loss of power that would occur at high RPM, street car diesels have a bypass valve that activates past 2500 or so rpm and bypasses the filter. During that time the oil in the engine is basically unfiltered.
Given that commercial diesel engines run at much lower engine speeds, the filter's resistance to flow is much less of an issue and so it never need be bypassed, and thus the oil stays cleaner.
Or so i was explained.
Pumaracing said:
Diesel oil is pretty high detergent anyway. It has to be to keep as much of the nasty black grot in suspension as possible. I'd just stick to a synthetic oil of the recommended grade, change it regularly and leave it at that.
As an aside do you know why engines wear out in the first place? It isn't the oil quality although of course better oil helps. However commercial diesels have routinely lasted for over 500,000 miles (or 20,000 hours run time before rebuild) going back well before synthetic oils were ever invented. It's actually the filtration, or lack of it, that causes wear. 99% of the wear that takes place in any engine is due to contaminants inhaled through the induction system and the resulting wear particles not getting filtered out quickly enough or finely enough by the oil system.
Commercial diesels (ships, trucks, power generation engines etc) have much higher quality induction and oil filtration systems than cars. Partly because there is more space to fit them and partly because the engine cost and vehicle lifespan makes it worthwhile. Apart from taxis cars don't generally run for long enough to make it worthwhile fitting 500,000 mile spec filtration systems. If they had them though there's no doubt they'd last for much longer than is normally possible.
With the right filtration you could run modern engines on the oils available 30 or 40 years ago and they'd be perfectly happy until the chassis had rotted away long before the engine ever broke down.
On that line of thought...for someone who maybe does a lot of miles....how about more regular filter changes, and oil top ups ?As an aside do you know why engines wear out in the first place? It isn't the oil quality although of course better oil helps. However commercial diesels have routinely lasted for over 500,000 miles (or 20,000 hours run time before rebuild) going back well before synthetic oils were ever invented. It's actually the filtration, or lack of it, that causes wear. 99% of the wear that takes place in any engine is due to contaminants inhaled through the induction system and the resulting wear particles not getting filtered out quickly enough or finely enough by the oil system.
Commercial diesels (ships, trucks, power generation engines etc) have much higher quality induction and oil filtration systems than cars. Partly because there is more space to fit them and partly because the engine cost and vehicle lifespan makes it worthwhile. Apart from taxis cars don't generally run for long enough to make it worthwhile fitting 500,000 mile spec filtration systems. If they had them though there's no doubt they'd last for much longer than is normally possible.
With the right filtration you could run modern engines on the oils available 30 or 40 years ago and they'd be perfectly happy until the chassis had rotted away long before the engine ever broke down.
Lots of modern engines run very small filters...which really cant be a good thing given some service milages.
Dont put flushing oil in a PD engine mate.
I belive that particular engine requires the correct oil in if not it doesnt like it very much. This is what i found out when i was looking into getting one myself a few years ago.
If you want to clean it a little better then just change the oil a few times over the next few months.
I used to have a show car and i changed the oil once a month after a few times of doing it the oil stayed as clear as it was when it went it. I no this is way OTT but i only had to pay for a few quid for a filter didnt pay for the oil as i worked in a garage at the time.
I belive that particular engine requires the correct oil in if not it doesnt like it very much. This is what i found out when i was looking into getting one myself a few years ago.
If you want to clean it a little better then just change the oil a few times over the next few months.
I used to have a show car and i changed the oil once a month after a few times of doing it the oil stayed as clear as it was when it went it. I no this is way OTT but i only had to pay for a few quid for a filter didnt pay for the oil as i worked in a garage at the time.
theshrew said:
Dont put flushing oil in a PD engine mate.
I belive that particular engine requires the correct oil in if not it doesnt like it very much. This is what i found out when i was looking into getting one myself a few years ago.
If you want to clean it a little better then just change the oil a few times over the next few months.
I used to have a show car and i changed the oil once a month after a few times of doing it the oil stayed as clear as it was when it went it. I no this is way OTT but i only had to pay for a few quid for a filter didnt pay for the oil as i worked in a garage at the time.
Cheers aye, like I said, it's been serviced every 10k and now I'm changing the oil every 5k I don't think it's worth it.I belive that particular engine requires the correct oil in if not it doesnt like it very much. This is what i found out when i was looking into getting one myself a few years ago.
If you want to clean it a little better then just change the oil a few times over the next few months.
I used to have a show car and i changed the oil once a month after a few times of doing it the oil stayed as clear as it was when it went it. I no this is way OTT but i only had to pay for a few quid for a filter didnt pay for the oil as i worked in a garage at the time.
I just like to cover all the bases when I get a new car. Although it's had a full service I've just changed all the filters and brake fluid and am getting the cambelt done in 5k so I can baseline it basically. I aim to put another 100k on it as it's perfect for my work commute - 50-odd mpg but a good amount of torque for getting past lorries and hypermilers when needed.
Kaboom said:
The thing with such high filtration is right in line with what FoolOnTheHill said.
Commercial diesels run at much lower RPM than street car diesels. Trucks, buses, generators very rarely spin past 1500-2000rpm while my Ford Focus generally sees quite a bit of action past 3500.
The filter's resistivity to the oil's flow is what saps power from the engine, and it rises with the square of engine speed. To prevent the huge loss of power that would occur at high RPM, street car diesels have a bypass valve that activates past 2500 or so rpm and bypasses the filter. During that time the oil in the engine is basically unfiltered.
Given that commercial diesel engines run at much lower engine speeds, the filter's resistance to flow is much less of an issue and so it never need be bypassed, and thus the oil stays cleaner.
Or so i was explained.
The way Volvo boat engines achieve a higher level of filtration is to have a seperate fine oil filter that the oil expelled by the bypass valve passes through at relatively low pressure on the way back into the sump. The pressure relief valve is mounted on the outside of the block and pipes run from it to the remote filter assembly as well as the oil cooler. There is also a pressure relief valve in the main oil filter housing that allows the oil to bypass a blocked filter and continue to lubricate the engine, not an ideal situation but better than a wrecked £25k engine! When the engines are hot the main pressure relief valve opens at some 1000rpm and at idle (600rpm) when cold. There is also a seperate oil feed to the piston cooling oil jets that spray oil onto the underside of the piston crowns and this feed has a valve that opens at 25psi so as not to take oil pressure away from the main components of the engine when at hot idle,Commercial diesels run at much lower RPM than street car diesels. Trucks, buses, generators very rarely spin past 1500-2000rpm while my Ford Focus generally sees quite a bit of action past 3500.
The filter's resistivity to the oil's flow is what saps power from the engine, and it rises with the square of engine speed. To prevent the huge loss of power that would occur at high RPM, street car diesels have a bypass valve that activates past 2500 or so rpm and bypasses the filter. During that time the oil in the engine is basically unfiltered.
Given that commercial diesel engines run at much lower engine speeds, the filter's resistance to flow is much less of an issue and so it never need be bypassed, and thus the oil stays cleaner.
Or so i was explained.
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