Why would a engine use straight non det 30wt oil?
05-18-2009, 07:35 PM
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Why would a engine use straight non det 30wt oil? While at a friends house he has a engine that says to only use 30 weight Non-detergent oil Why ?
What would happen if you put a detergent any grade oil in lets pick a 15-50 cause 30 is close to the middle ?
What would happen if you put a detergent any grade oil in lets pick a 15-50 cause 30 is close to the middle ?
05-18-2009, 08:12 PM
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Detergents make foam. Usually when an engine requires non-detergent formula oils, it is to prevent foaming. Some small engines with oil slingers will generate a lot of foam if you use an oil containing detergents. Also, many compressors require non-detergent oil.
Shane
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05-19-2009, 04:06 AM
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via practical handbook machinery lubrication:
detergent = component (additive) of engine oil that helps control varnish ring zone deposits, and rust by keeping insoluble particles in colloidal suspension, and in some cases by neutralizing acids. A detergent is usually a metallic (calcium, barium, magnesium) compound, such as sulphonate, phosphonate, thiophosphonate, phenate, or salicylate. Because of the metallic composition, an oil with a detergent additive will leave ash when burned.
a detergent is normally used in conjuction with a dispersant,
dispersant has same function as detergent for most part but different mainly by being a non-metallic compound and does not leave an ash when burned, hence ashless dispersant.
i am not aware of detergents being the cause of oil foaming, or aerating. In general, any base oil can foam under certain conditions and will aerate. This is why there's a specific additive called ant-foaming agents, they reduce surface tension so entrapped air will escape faster. I believe they are silicon based, and are what show up in oil analysis reports on some oils. Ford powerstroke diesels, specially the mid-1990's 7.3L, used engine oil as a hydraulic fluid to actuate the fuel injectors, and there is an anti-foaming requirement for that because engine oil was pressurized to around 3000 psi if i remember correctly. Lots of stories where someone would change their oil and use a non API-Cx rated oil (would only have API-SJ or API-SL) and they would have performance issues because the oil would foam under the pressure and the injectors wouldn't operate correctly.
the main reason a non-detergent oil was called for is that the engine typically burnt oil and for that time period it was known the detergent type oils would leave deposits and do more harm than good. And detergent oils are formulated to combat the byproducts of combustion in a combustion engine. Something like an air compressor does not have combustion, so there is no need for a detergent oil and in this case any oil that gets into the cylinder under the heat of compression may leave deposits if it were a "detergent" oil. So generally a non-detergent oil is recommended. And for an air compressor using an oil slinger, a non-detergent oil will most certainly aerate and you can easily see that if there is a sight glass on the crankcase, but this is of little consequence because there is no oil pump and the oil is not pressurized.
But don't confuse detergents with rust/corrosion inhibitors, they are different and most all oils or lubricating/hydraulic fluids have rust/corrosion inhibitor additives along with anti-foaming agents. Detergents in an engine oil is what keep the internal engine parts clean, because all that dirt is suspended in the oil then leaves the engine when the oil is changed. Use a non-detergent oil and the oil will stay clean longer and retain it's golden clear color but all that dirt and byproducts from combustion will accumulate on internal engine parts and settle to the bottom of the oil pan eventually. I also remember hearing something about engine design where it was desirable to use a non-detergent oil where the rationale was so that all the dirt could settle to the bottom of the oil pan and could be removed by dropping and cleaning the pan.
what is the engine calling for non-detergent oil?
your second question of using SAE 15w-50 in place of a SAE 30 or SAE 10w-30 has to do with viscosity. The second number (50 or 30) has to do with viscosity at 100C operating temperature. A 30 weight oil has a viscosity range of 9-12.5 centistokes whereas a 50 weight has 16-22 cSt. 40 weight is 12.5 - 16 cSt.
The first numer, before the "W" is the winter weight and is a specification based on the pumping viscosity at cold temperatures, and the unit is centipoise (cP). The cSt unit is kinematic viscosity at high temperatures and reflects time it takes for oil at given temperature to flow through a certain sized orifice, the cP reflects how easy it is to move oil when it is thick at cold temperatures.
The specs are as follows:
1 cP = 1 mPA s
1 cSt = 1mm^2/s
[grade] [borderline pump temp deg C] [cP at temp C]
0W -35 3250@-30
5W -30 3500@-25
10W -25 3500@-20
15W -20 3500@-15
20W -15 4500@-10
25W -10 6000@-5
detergent = component (additive) of engine oil that helps control varnish ring zone deposits, and rust by keeping insoluble particles in colloidal suspension, and in some cases by neutralizing acids. A detergent is usually a metallic (calcium, barium, magnesium) compound, such as sulphonate, phosphonate, thiophosphonate, phenate, or salicylate. Because of the metallic composition, an oil with a detergent additive will leave ash when burned.
a detergent is normally used in conjuction with a dispersant,
dispersant has same function as detergent for most part but different mainly by being a non-metallic compound and does not leave an ash when burned, hence ashless dispersant.
i am not aware of detergents being the cause of oil foaming, or aerating. In general, any base oil can foam under certain conditions and will aerate. This is why there's a specific additive called ant-foaming agents, they reduce surface tension so entrapped air will escape faster. I believe they are silicon based, and are what show up in oil analysis reports on some oils. Ford powerstroke diesels, specially the mid-1990's 7.3L, used engine oil as a hydraulic fluid to actuate the fuel injectors, and there is an anti-foaming requirement for that because engine oil was pressurized to around 3000 psi if i remember correctly. Lots of stories where someone would change their oil and use a non API-Cx rated oil (would only have API-SJ or API-SL) and they would have performance issues because the oil would foam under the pressure and the injectors wouldn't operate correctly.
the main reason a non-detergent oil was called for is that the engine typically burnt oil and for that time period it was known the detergent type oils would leave deposits and do more harm than good. And detergent oils are formulated to combat the byproducts of combustion in a combustion engine. Something like an air compressor does not have combustion, so there is no need for a detergent oil and in this case any oil that gets into the cylinder under the heat of compression may leave deposits if it were a "detergent" oil. So generally a non-detergent oil is recommended. And for an air compressor using an oil slinger, a non-detergent oil will most certainly aerate and you can easily see that if there is a sight glass on the crankcase, but this is of little consequence because there is no oil pump and the oil is not pressurized.
But don't confuse detergents with rust/corrosion inhibitors, they are different and most all oils or lubricating/hydraulic fluids have rust/corrosion inhibitor additives along with anti-foaming agents. Detergents in an engine oil is what keep the internal engine parts clean, because all that dirt is suspended in the oil then leaves the engine when the oil is changed. Use a non-detergent oil and the oil will stay clean longer and retain it's golden clear color but all that dirt and byproducts from combustion will accumulate on internal engine parts and settle to the bottom of the oil pan eventually. I also remember hearing something about engine design where it was desirable to use a non-detergent oil where the rationale was so that all the dirt could settle to the bottom of the oil pan and could be removed by dropping and cleaning the pan.
what is the engine calling for non-detergent oil?
your second question of using SAE 15w-50 in place of a SAE 30 or SAE 10w-30 has to do with viscosity. The second number (50 or 30) has to do with viscosity at 100C operating temperature. A 30 weight oil has a viscosity range of 9-12.5 centistokes whereas a 50 weight has 16-22 cSt. 40 weight is 12.5 - 16 cSt.
The first numer, before the "W" is the winter weight and is a specification based on the pumping viscosity at cold temperatures, and the unit is centipoise (cP). The cSt unit is kinematic viscosity at high temperatures and reflects time it takes for oil at given temperature to flow through a certain sized orifice, the cP reflects how easy it is to move oil when it is thick at cold temperatures.
The specs are as follows:
1 cP = 1 mPA s
1 cSt = 1mm^2/s
[grade] [borderline pump temp deg C] [cP at temp C]
0W -35 3250@-30
5W -30 3500@-25
10W -25 3500@-20
15W -20 3500@-15
20W -15 4500@-10
25W -10 6000@-5
Last edited by 1 FMF; 05-19-2009 at 04:28 AM.
