Oil sludge
Oil sludge or black sludge is a gel-like or semi-solid deposit inside an internal combustion engine, that can create a catastrophic buildup. It is an emulsion of engine oil soluble combustion productions, water and solids.[1][2] Particles accumulating in the sludge, can cause excessive engine wear.[3][4] The sludge can also block the oil pump inlet screen or oil channels, causing oil starvation.[2][5]
One type of sludge is called 'hot sludge' and is formed when engine oil oxidizes at high temperatures.[4] Cold sludge is formed when engines don't get up to operating temperature, for example when the vehicle is primarily driven short distances.[6]
Causes
[edit]Oil sludge may occur due to a variety of different factors. Some of the most common causes are:[additional citation(s) needed]
- Defective crankcase ventilation system
- Oil/coolant contamination
- Neglecting oil changes[7]
- Low oil level
- Poor engine design[7]
- Quality of the fuel[8]
Prior to the phase out of leaded fuel, oil sludge consisted of up to 50% lead by weight.[3]
Precautions
[edit]Oil sludge is generally preventable through frequent oil changes at manufacturer specified intervals,[9] however, while uncommon, some engines do have a tendency to build up more sludge than others.
Engine oils typically contain dispersant additives to inhibit sludge formation.[8]
In response to oil sludge problems, car manufacturer started adding oil life monitors to vehicles to warn drivers to change the engine oil on time.[10]
Examples
[edit]Sludge formation was first found in combustion engines in the 1960s.[5] During the 1980s sludge formation became a common issue again.[11]
In 2004, Volkswagen informed 426,000 Passat and Audi A4 owners in the US warning them of sludge problems with its 1.8-liter turbocharged engines.[10]
In 2007, Toyota settled a lawsuit with 7.5 million vehicle owners on sludge formation, although the company insisted the issue primarily occurred for vehicles which weren't serviced frequently enough.[7][12]
References
[edit]- ↑ Rogers, D. T.; Rice, W. W.; Jonach, F. L. (1956-01-01). "Mechanism of Engine Sludge Formation and Additive Action". SAE Technical Paper Series. Vol. 1. doi:10.4271/560067.
- 1 2 Haycock, Roger F.; Hillier, John E. (2005-07-01). Automotive Lubricants Reference Book. John Wiley & Sons. ISBN 978-1-86058-471-8.
- 1 2 Costs and Benefits of Reducing Lead in Gasoline. Office of Policy Analysis, Office of Policy, Planning, and Evaluation, U.S. Environmental Protection Agency. 1984.
- 1 2 "Vehicle Engine Sludge | Consumer Reports". www.consumerreports.org. Retrieved 2026-09-18.
- 1 2 Lillywhite, J.R.F.; Sant, P.; Saville, S.B. (1990-01-01). "SLUDGE FORMATION: INVESTIGATION OF SLUDGE FORMATION IN GASOLINE ENGINES". Industrial Lubrication and Tribology. 42 (1): 4–10. doi:10.1108/eb053400. ISSN 0036-8792.
- ↑ Dimitroff, Edward; Quillian, R. D. (1965-02-01). "Low Temperature Engine Sludge — What? — Where? — How?". SAE Technical Paper Series. Vol. 1. doi:10.4271/650255.
- 1 2 3 Brooks, Michael (2007-01-09). "TOYOTA DEAL: HERE COMES THE SLUDGE JUDGE". The Center for Auto Safety. Retrieved 2026-09-18.
- 1 2 Monopoly, United States Congress Senate Committee on the Judiciary Subcommittee on Antitrust and (1971). Marketing Practices in the Gasoline Industry: Hearings Before the Subcommittee on Antitrust and Monopoly of the Committee on the Judiciary, United States Senate, Ninety-first [and Ninety-second] Congress Pursuant to S. Res. 334 [and 32, Section 4]. U.S. Government Printing Office.
- ↑ Palafox, J. A. (April 2012). How to Keep Your Vehicle Running Like a Dream. Xlibris Corporation. ISBN 978-1-4691-9551-3.
- 1 2 Guilfoyle, Nicole (2004-09-07). "Monitors Could Combat Oil Sludge". The Center for Auto Safety. Retrieved 2026-09-18.
- ↑ "Club Evolution - The Return of the Black Death". www.clubevolution.com.au. Retrieved 2026-09-18.
- ↑ "Toyota settles owners' lawsuit over oil sludge". Los Angeles Times. 2007-01-12. Retrieved 2026-09-18.