9.2 Is coolant mixing with your engine's oil? Water and coolant reduce the lubrication properties of the oil and causes metal corrosion while the glycol (coolant) breaks down at high temperatures, causing a sludge buildup in the engine. Water typically gets into the oil through cracked heads and blown gaskets, which are undetectable to the naked eye.
9.3 How can dirt or foreign materials get into an engine if it's completely sealed off? Simple: Contaminated fuel, a loose dip stick, defective valve-cover gaskets, PCV valves or a defective air cleaner will cause dirt to infiltrate the engine's oil supply, leading to excessive engine wear. Turbos without air filters are highly susceptible to this problem.
9.4 Crack open the oil cap and take a big whiff of the underside. If the smell of burnt oil fills your nostrils, the car has more than likely run without oil changes. Use a flashlight to inspect the engine's internals through the filler neck. If you notice a dark oil coating baked onto the internals or oil sludge buildup surrounding the camshafts or cam holders, the oil hasn't been changed regularly and the engine internals are more than likely worn.
10.1 Gray to light golden-brown color:This condition is ideal for optimum spark and ignition timing. The spark plug and air/fuel mixture are operating properly.
10.2 Dry (carbon fouling) with black soot buildup:A dry, black carbon plug indicates the engine is running an air/fuel mixture that is too rich. Fouling can be attributed to a spark plug heat range that is too cold for the operating conditions or ignition system problems causing an erratic or weak spark.
10.3 Wet (oil fouling) with a shiny, wet, black appearance:Wet or oily deposits covering a spark plug usually mean the piston rings are weak or valve guides aren't sealing properly. Improperly gapped ring lands or improperly seated oil rings with many of the aftermarket pistons sold could be another culprit. Ignoring this problem will lead to a weak spark and eventual ignition misfire.
10.4 Excess deposits with bumpy, chalky buildup:Poor fuel quality causes the easy-to-recognize symptoms of a white, chalky substance covering both the tips and the electrode. An oil leak into the combustion chamber or cheap-quality oil can also cause this unsightly problem.
10.5 Overheated with white, blistered, melted electrode:This is known as the "Michael Jackson" symptom where the electrode is literally burned away. The core nose has burned off while sporting a glazed appearance. Many nitrous oxide or turbocharged vehicles experience this problem due to a lean air/fuel mixture or using a spark plug with a heat range that is too hot for the engine's operating conditions. Aggressive timing and shitty-octane fuel can also contribute to this condition.
10.6 Detonation with black or diamond speckles:Detonation shows up on the plugs as minute dots or specks on the porcelain. There are two different types of spotting. One type appears as black spots and the other appears as little, bright, diamond-like spots. The black spots (similar to pepper sprinkled on a plug) indicate there was too much heat on the plug, which causes detonation by having the heated plug fire off the mixture prior to the spark firing. The diamond spots are bits of aluminum from the piston or cylinder head sheering off your internals and making their way onto the plug. Vehicles sporting high compression or high boosts are no stranger to these plugs. Increasing octane fuel can help in this situation.