Kebingungan deskripsi enncer-kental pada oli multigrade sudah lama terjadi. Daripada bingung-bingung yah sutra, ikuti saja deskripsi dari para pabrikan oli. Logikanya oli semakin panas semakin encer tapi deskripsi dari pabrik oli misalnya dari castrol :
HOW IS VISCOSITY MEASURED?
The viscosity of oil changes with temperature, therefore multigrade oils were developed to provide protection across a range of operating temperatures. The SAE (Society of Automotive Engineers) scale shows the viscosity of oil at both hot and cold temperatures. That’s why the viscosity grade on the oil bottle is made up of two numbers.
LOW TEMPERATURES
The first number followed by the letter W describes the viscosity of oil at low temperatures (the W stands for winter). The lower the number the thinner the oil. A thinner oil at low temperatures is good because it flows more easily and is therefore able to protect the engine when it is first started from cold. If oil is too thick when cold, it will not circulate freely and will reduce fuel economy.
HIGH TEMPERATURES
The second number describes how thick the oil is at the engine’s normal operating temperature. The higher the second number, the thicker the oil. If it's too thin when hot, it may not protect effectively. If it's too thick, you lose efficiency.
Jadi pada oli multigrade maka "A thinner oil at low temperatures" dan "thicker oil at engine’s normal operating temperature"
Kalau kita artikan thinner="lebih tipis/encer" dan thicker="lebih tebal/kental" maka pemahamannya kan oli encer pada suhu rendah dan menjadi lebih kental pada suhu tinggi. Nah bingung kan dengan logika.
Belajar lebih lanjut di :
http://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htm
Disitu lengkap dijelaskan tentang sifat-sifat olie yang memang menjadi lebih encer pada suhu lebih tinggi. Terus bagaimana pernyataan dari pabrikan oli :
The second number describes how thick the oil is at the engine’s normal operating temperature.
Q: I own a 1994 GMC 3/4-ton van with a 350 engine. In the last year, the oil pressure has been low, just above the red, and the low warning indicator is on at idle. When I speed up, the pressure goes up. I change the oil every 4,000 miles. At the last oil change I changed it to 10W-40 although the manual calls for 5W-30; this seems to have helped the oil pressure. Is it OK to continue with 10W-40 oil? The van has 145,000 miles on it.
A: Yes. This is a practical method to improve oil pressure in an older, high-mileage engine. The slightly thicker oil film from the heavier base weight oil — 10W — can help protect worn engine bearings as well. As long as you're not hearing knocking or serious mechanical noises from the engine, the heavier oil should buy you many more miles of service from your vehicle. Over the decades of buying and driving older, high-mileage vehicles, I've even used 15W-40 and 20W-50 oils in high-mileage engines to improve oil pressure and extend their service life.
Historically, with older engines having looser clearances from wear, and especially in the Mini/1100/Metro’s (with the gearbox in the sump resulting in rampant shear damage to the VI Improvers), these engines still generally require a thicker oil such as a mineral 20W50 or 15W40. In fact it was the launch of the Mini in 1959 that resulted in the 20W50 scenario with BMC/BL products. The shearing damage on the typical 15W40 caused problems and I am told by reliable sources that the resulting 20W50 was selected to counter this shearing action. 20W50 then seemingly became the defacto oil choice for BL products in the 1970s and is trotted out as the required specification on every forum irrespective of the ambient temperatures.
In the case of the B Series engine, it must be remembered that the early units used in the MGB between 1962 and 1965 were also a 3 main bearing design and owing to bearing failure I am told the required viscosity was increased. In addition a cooler was added as standard yet this is often quoted by MG mechanics as being unnecessary and that a thermostat is recommended. In this case, with a 5 main bearing engine and a cooler without a thermostat one must wonder if a 20W50 is right for these engines or not? A high VI 10W40 or 0W40 would surely suffice?
20W50 is still used in more modern cars only where extreme ambient heat is encountered for some of the off-road 4x4 pick-ups, such as in Western Australia and the Middle East
The second number describes how thick the oil is at the engine’s normal operating temperature.
The higher the second number, the thicker the oil. If it's too thin when hot, it may not protect effectively. If it's too thick, you lose efficiency.Akhirnya penjelasan lebih gamblang ada di : http://news.transdiesel.com/blog/multi-grade-oil
May 23, 2013 - 3:15 PMhttp://m.startribune.com/brand-heavier-oil-can-help-high-mileage-engines/208709221/ By PAUL BRANDJadi oli SAE 15W-40 mempunyai viskositas yang mirip SAE15W pada suhu rendah(-25 C) dan mempunyai viskositas mirip SAE 40 pada suhu tinggi(100 C). Tetap saja oli 15W-40 pada 100 C lebih encer daripada saat suhu lebih rendah, TETAPI jauh lebih kental dari oli SAE 15W pada 100 C. Bahkan lebih tinggi viskositas olie SAE15W-40 daripada viskositas oli SAE40 pada suhu diatas 100 C. Jadi walau Indonesia rata-rata bersuhu 25 C keatas dan tidak pernah bersalju, oli multigrade mempunyai keunggulan di suhu diatas 100 C, lebih tinggi viskositasnya, lebih melindungi mesin pada suhu tinggi.Pada mobil tua direkomendasikan oli high milleage dan berviskositas tinggi,contohnya :
Q: I own a 1994 GMC 3/4-ton van with a 350 engine. In the last year, the oil pressure has been low, just above the red, and the low warning indicator is on at idle. When I speed up, the pressure goes up. I change the oil every 4,000 miles. At the last oil change I changed it to 10W-40 although the manual calls for 5W-30; this seems to have helped the oil pressure. Is it OK to continue with 10W-40 oil? The van has 145,000 miles on it.
A: Yes. This is a practical method to improve oil pressure in an older, high-mileage engine. The slightly thicker oil film from the heavier base weight oil — 10W — can help protect worn engine bearings as well. As long as you're not hearing knocking or serious mechanical noises from the engine, the heavier oil should buy you many more miles of service from your vehicle. Over the decades of buying and driving older, high-mileage vehicles, I've even used 15W-40 and 20W-50 oils in high-mileage engines to improve oil pressure and extend their service life.
Dan http://www.kewengineering.co.uk/Auto_oils/oil_viscosity_explained.htmHowever, these VI Improver additives are susceptible to shearing damage from the mechanical components and would lose some of their performance, resulting in 20W50 oil acting more like 15W40 oil. This damage can happen very early in the life of the oil and is seen as part of the bedding in of the oil following an oil change. This is why the oil pressure often appears to have improved just after a fresh oil change as the oil is yet to bed in so is consequently thicker giving a false impression of improved oil pressure.
Historically, with older engines having looser clearances from wear, and especially in the Mini/1100/Metro’s (with the gearbox in the sump resulting in rampant shear damage to the VI Improvers), these engines still generally require a thicker oil such as a mineral 20W50 or 15W40. In fact it was the launch of the Mini in 1959 that resulted in the 20W50 scenario with BMC/BL products. The shearing damage on the typical 15W40 caused problems and I am told by reliable sources that the resulting 20W50 was selected to counter this shearing action. 20W50 then seemingly became the defacto oil choice for BL products in the 1970s and is trotted out as the required specification on every forum irrespective of the ambient temperatures.
In the case of the B Series engine, it must be remembered that the early units used in the MGB between 1962 and 1965 were also a 3 main bearing design and owing to bearing failure I am told the required viscosity was increased. In addition a cooler was added as standard yet this is often quoted by MG mechanics as being unnecessary and that a thermostat is recommended. In this case, with a 5 main bearing engine and a cooler without a thermostat one must wonder if a 20W50 is right for these engines or not? A high VI 10W40 or 0W40 would surely suffice?
20W50 is still used in more modern cars only where extreme ambient heat is encountered for some of the off-road 4x4 pick-ups, such as in Western Australia and the Middle East
Mobil tua termasuk mobil lelah (high mileage) maka seal dan mekanik sudah kendor. Terjadi kebocoran oli, terjadi pembakaran oli. Knalpot asapnya jadi ngebul, olie dalam mesin berkurang. Penyebab oli berkurang tidak selalu karena bocor dan terbakar, tetapi juga karena oli "rusak" (damaged). Oli menjadi lebih encer dari seharusnya dan akhirnya menguap. Kembali ke oli high mileage, oli ini ditambahi zat aditif dan diformulakan agar mengencangkan seal yg kendor, dan mengurangi konsumsi oli.
sumber :
http://www.cenex.com/about/cenex-information/cenexperts-blog-page/oil-and-lubricants/high-mileage-oils
Oli High mileage tidak harus berviskositas tinggi, di barat bisa mempunyai SAE 5W-30 karena suhu ekstrim dingin di musim dingin. Di indonesia saya belum menemukan oli high mileage.
sumber :
http://www.cenex.com/about/cenex-information/cenexperts-blog-page/oil-and-lubricants/high-mileage-oils
Oli High mileage tidak harus berviskositas tinggi, di barat bisa mempunyai SAE 5W-30 karena suhu ekstrim dingin di musim dingin. Di indonesia saya belum menemukan oli high mileage.
Dari uraian diatas, untuk mobil tua yang mulai ngebul asap knalpotnya direkomendasikan menggunakan olie SAE 20W-50. Apa mereknya? Tanya ke bengkel atau komunitas :D
Semoga tulisan ini menjadi pencerahan,
Terima Kasih.
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