Why Does Diesel Oil Turn Black? Why Is Diesel Oil So Dark?

in this video we're going to be discussing what causes diesel engine oil to turn so dark so quickly hey so today we're gonna be discussing why diesel engine oil turns black so quickly compared to say gasoline engine oil when I was a teenager and not mechanically inclined and my father who's never been mechanically inclined bought a diesel tractor after running it a few days he noticed that the engine oil was really really dark and he thought something was wrong and me not knowing what I know now I thought something was wrong as well and it turns out that black engine oil and a diesel engine is fairly normal but why is that obviously there's a design or operational difference between diesel and gasoline that causes the engine oil to turn dark quickly now Diesel's have many differences between gasoline engines one being the fuel one being much higher compression ratios Diesel's typically run turbochargers opposed to gasolines which do not although some do but it's more common that they do not so something's different and what it is is soot now gasoline does produce soot as well however it is much less than a diesel engine and the reason is gasoline and the air that it is ignited with is typically mixed before it enters the combustion chamber whereas diesel is injected directly into the combustion chamber at the point of combustion so under varying conditions such as at idle when the engines not up to full operating temperature quick rpm changes if you're running a rich condition meaning let's say you have a plugged air filter or your engine is not at boost or you have a over fuelling injector or you have hot rodded injectors you're going to be getting more black exhaust smoke now almost all that smoke goes out the exhaust if you've seen an older diesel engine know what I'm talking about if you've seen an exhaust leak you know what I'm talking about but a small percentage of that gets passed the piston rings and why is that well this is a piston ring do you see the gap okay most Pistons have three rings and these gaps will allow a small amount of combustion gases and exhaust to pass through them into the engine now this is known as blow by and the amount of blow by is a good determination of how your engines operating but if you're producing lots of soot say long idle times over fuel injectors rich conditions you're gonna get carbon soot into your oil now this is normal and you may be thinking Oh newer diesel engines you don't see black exhaust smoke well that doesn't mean they're not producing soot it just means that there's something called a DPF that is catching the soot which stands for diesel particulate filter now this is catching the soot that the engine is releasing and not allowing it to come up the exhaust but it's does not prevent the soot getting past the Rings and into your crankcase now newer engines will produce on average a little less soot and this has to do with more advanced combustion processes as well as high pressure common rail fuel systems which will operate a little more efficiently now is this soot bad for your engine in high amounts yes so if your engine has very high amounts of blow by the soot can actually get to a point where it starts plugging your oil filter and you'll see reduced oil pressures however the soot molecules are very small they're 0.3 microns on average so that is incredibly small much smaller than the size of let's say a dust particle or human hair so on average you're never gonna see damage from these soot particles but over time they can't accumulate to the point where that oil needs to be changed so since it takes a while to accumulate you might be wondering why after an oil change is the engine oil black almost instantly well when you do an oil change even if you do the filter and the oil there's still a lot of oil in your system you may not realize that so even if you drain the pan there's still oil in the pan ask me I pulled a lot of oil pans I've never had one come off and it's fully empty that might not be a lot so what else contains oil when you drain your oil well your oil galleys do so you have your your main oil galley your crankshaft has oil in it your camshaft or your camp chef doesn't contain oil but the bearings in the oil galley to it do there's oil in the recesses in the head and the rocker arm shafts your oil cooler holds a lot of oil the air compressor will hold oil just a lot of places where that oil is gonna see you can have up to a gallon of oil still in your system and that engine oil with the soot will contaminate the new oil and make it look dark very quickly that does not mean the oil is bad however it just has the appearance of older oil quicker and there's not a lot you can do with this about this without changing components so don't worry about it also soot is almost like a dye any one that wears white undershirts like me and works in this field will notice that no matter what you do if you get engine oil on your shirts you can watch them with bleach wash them with hot water that does not come out and a very small amount will make your clean engine oil look dirty it's not it's just a property of the suit it's almost like a dye okay hope you enjoy the video if you did like and subscribe thank you [Music]

Channel: Adept Ape

Views: 394,154

Rating: 4.8981714 out of 5

Keywords: Diesel Engine Oil, Common Rail Fuel System, Engine Soot, Engine Oil Black, Diesel Mechanic, Diesel Video, Diesel Exhaust, Caterpillar Engine, Cummins Engine, Detriot Engine, International Engine, Merc

Id: QLnof-IMNBo

Length: 6min 20sec (380 seconds)

Published: Sun Jan 22 2017