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LO 10-6 Identify and describe the purpose, types, and operation of oil filtration systems

Site: CDX Learning Systems
Course: DE Section 2-1: Engine Blocks and Cylinder Heads
Book: LO 10-6 Identify and describe the purpose, types, and operation of oil filtration systems
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Date: Thursday, 5 November 2026, 7:44 PM

Table of contents

1. Filtration Systems

LO 10-06: Identify and describe the purpose, types, and operation of oil filtration systems.

 

Filtration Systems

Almost all diesel engine lubrication systems use full-flow lubrication. This means any oil reaching internal engine parts has passed through an oil filter. To increase the amount of filtration performed by a lubrication system, a supplemental, partial-flow—or bypass—filtration circuit is also used. Engine oil is filtered through an oil bypass filter and returned directly to the sump. No oil passing through the bypass filter actually reaches moving engine parts Figure 52.

 

   Fig10_52

FIGURE 10-52: A supplemental filtration circuit contains a bypass filter. The bypass filter adds extra capacity to the oil filtration system.

 

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1.1. Types of Oil Filters: Cartridge Versus Spin-On

LO 10-06: Identify and describe the purpose, types, and operation of oil filtration systems.

 

Types of Oil Filters: Cartridge Versus Spin-On

Spin-on filters, which are enclosed in a metal can that is threaded onto a filter header, were introduced during the 1950s and made changing oil easier and less messy. Since the late 1980s, however, European and North American engine manufacturers have been reverting to the cartridge filters because of a number of problems associated with the use of spin-on filters. One problem is the availability of engine compartment space for filters. Because space is at a premium in the engine compartment of today’s vehicles, the oil filter can be very difficult to locate and change. New cartridge filter housings are usually conveniently located on the top or side of the engine compartment, making them easily accessible. Cartridge filter housings are typically designed with a screw-on cap and a single sealing gasket Figure 53. The housings are ventilated when opened, and the oil flows out of the filter cavity and back to the sump through a separate drain system. Messy spills associated with spin-on filters are eliminated with the internal drain system used by cartridge filters.

Another advantage of a cartridge filter is that it costs significantly less than a spin-on filter. It is reported that almost 80% of the cost of a spin-on filter is due to the steel canister and internal bypass valves. With a cartridge filter, only the pleated media and a gasket are replaced during filter service. This not only reduces the cost but also eliminates unnecessary waste of natural resources. Cartridge filters also allow OEMs to establish standardized oil filter cartridge sizes, reducing the number of different cartridges required to service a particular brand of vehicle or engine.

 

   Fig10_53

FIGURE 10-53: Cartridge filters are quickly replacing spin-on filters for environmental, spatial, and accessibility reasons.

 

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1.2. Filter Disposal and the Environment

LO 10-06: Identify and describe the purpose, types, and operation of oil filtration systems.

 

Filter Disposal and the Environment
The most important reason for the transition from spin-on to cartridge filters is spin-on filter disposal. The disposal cost of a cartridge filter is far less than that of a spin-on filter, which requires special handling procedures to be exempt from EPA regulations regarding hazardous waste. In many jurisdictions, spin-on oil filters are exempt from hazardous waste regulation if the oil filter is:

  • Punctured through the dome end or anti-drainback valve, which normally prevents sludge from draining out of the filter, and hot-drained.
  • Hot-drained and crushed.
  • Hot-drained and dismantled.
  • Hot-drained using an equivalent method to remove used oil.

Hot-draining is defined as draining the oil filter at or near engine operating temperature. This means the filter is removed from the engine while it is still warm, then punctured or crushed and drained. Most of the oil is removed from the filter during hot-draining. The EPA further recommends hot-draining for a minimum of 12 hours.

  Technicians Tip  
  Oil filters are considered hazardous waste and must be disposed of accordingly. Environmental legislation regarding waste disposal carefully regulates how used filters are handled and finally disposed of.  

 

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