Many ways to know the state of the engine. One of them can be seen from the color and condition of the spark plug. If you have any free time this weekend, try to open the spark plug and see if such instructions below?
Brown: In the electrode slightly grayish brown sign plugs working normally, but approaching the lifetime limit. We recommend that you replace the new one.
Yellowish: Engine overheated, so the temperature and pressure of the engine rises excessively. Check engine cooling devices.
Obsolete: as worn spark plugs with a little pile of crust on the electrode. Busi has been rejected and need to replace new.
Redness: chipped electrode layer with the color red, but no crust. Engineering experience ovberheat, check code heat range and engine cooling devices.
Hirst: There is a pile of charred crust and colored electrodes. That is, setting the fuel is not true. check the supply of gasoline and other electrical devices.
Melt: Electrodes melted and scorched look, due to the spark plug with a heat range is wrong. Leak on engine components that cause the lubricant helped fire in the engine room.
The crust is thick: thick crust deposits on the spark plug electrodes and head due to poor fuel consumption. A leak in the seals in the valve that makes lubricants seeping down to the spark plugs.