Engine Sludge

Engine Sludge – E46,E53, E60, E65, E87, E90 (all with long service intervals – petrol engines – 2001 to current)

I have recently urged all my customers to do an oil service every 10000km or latest 15000km. It will prolong the life of the engine and will result in little or no build up of oil solids.

Sludge is a solid or gel in oil caused by the presence of water and accumulates with use. Put even more simply it’s a build up of product of over-stressed / used oil in the engine.

The on board computer’s interval is every 25000km and some will go to 30000km depending on driving style. This is far too long and will result in sludge and intricate engine parts failing. A sludgy engine is being damaged with every stroke. As the sludge sticks, there is less good oil to circulate and do its protective job. This coating of gel also stores heat instead of releasing it which stresses the radiator and cooling system

I have customers with mileage as little as 110000km experiencing the wrath of the sludge.

Most common complaints in early stages are:

• No power
• Internal parts failing (inlet and exhaust vanos units) – see picture 2 is a vanos unit for E46
• Car shaking or misfire.

More serious:

• Noisy engine
• Car goes into limp mode
• Oil temperature is higher and core temperature (block) is higher; cooling system problems
• Low oil pressure
• Car won’t start – engine seized

Sludge begins to appear in the oil sump and tappet cover. Inspecting the oil filler cap is not a definite test for sludge, as normal engines can have a small amount of sludge and condensation present at this high point of the crankcase.

“The oiling system in an engine is similar to the vascular system in a human body. It must absorb and release toxins, transfer heat, and suspend harmful particles until they can be filtered out. Unlike the blood in your body, though, engine oil is not self-renewing and has a limit to how much stress it can safely handle before it needs to be removed and refreshed.”

In the picture 1 above you will see a camshaft and the hydraulic lifters coated in sludge. This is the state of most of the cars that come in and the only way to solve this is to de-coke the engine by stripping it.

As your car is driven, oil is pumped under pressure from the oil sump up into the entire engine by the oil pump. The oil pump sends oil to the crankshaft and camshaft, and is squeezed into the oil galleries and pipes of the motor. The moving parts (crankshaft, valves, conrods and pistons) also splash oil onto other components in the crankcase, and finally it falls back into the oil sump.

While lubricating your engine’s moving parts at high temperatures, the oil carries combustion by-products and collects airborne dirt from the air-intake system. Circulating motor oil also suspends acids that are formed by chemical reactions in the crankcase.

Engine oil has a complex chemical job to do; additives in the oil work to suspend contaminants, inhibit corrosion, coat metal parts, keep viscosity stable, and slow oxidation.

Poor quality of oil is just as detrimental. I recommend synthetic oil. Synthetic motor oil is made from a blend of mineral oil and special additives. This combination makes the oil pure and hence can stand the strain form the engine.

Synthetic lubricants cost slightly more than conventional oils, but offer the best engine protection because:

• synthetics remain stable at high temperatures
• synthetics remain fluid at very low temperatures
• additive packages are formulated with special chemicals for top cleaning and anti-oxidant protection

From experience; I have had customers (1 series and 3 series E90) that just come off motor-plan and I have urged them to have oil services every 10000km. Their cars have reached mileages of over 200000km and I have never opened up their engines.

Bottom Line:

Modern cars are very complicated machines, Sludge is an expensive but preventable disaster.

Remember:

• Change oil every 10000km (max 15000km)
• Insist on good grade oil; synthetic oil
• Good additives work as vitamins for your engine

F.Y.I the older E36 generation of cars never had a problem with sludge and their intervals were every 12000km