Hydrogenated Nitrile/Highly saturated Nitrile
Auto Parts Spark Plug: Importance and Selection

When it comes to replacing spark plugs in your car, cost is always a factor to consider. New spark plugs can vary in price depending on the brand, material, and quality. It is important to understand the factors that contribute to the cost of spark plugs in order to make an informed decision.
Oil seals increasingly had to meet higher requirements, which is why PTFE was developed in 1980. This variant can better withstand higher engine speeds, higher oil temperatures, longer oil intervals and modern lubricants. In addition, the oil seal contains a wider contact surface, which ensures less wear.
MH: O.D. wall is a rubber material
HM: O.D. wall is a metal case
MH(S)H: O.D. wall is metal with a reinforced inner metal case
If there are curved seals, fit these to the engine. Smear sealant on the seal groove, stick the seal in place, and apply a blob of sealant to each end of the seal where it joins the gasket.
The edge of the metal is finely ground after seal manufacture in a centerless grinder to enable an interference fit in the oil seal housing. A slight chamfer on the outer diameter (OD) of the seal is desirable for easy assembly. The sealing lip is prepared by buffing, grinding or cutting away the rubber flash which occurs at the sealing edge. A fine sealing edge creates sufficient pressure on the shaft to minimise spring load, leading to lower friction whilst maintaining effective seal performance. The garter spring plays an important role in the efficiency of the oil seal. If its tension is too high, heat will be generated between the sealing lip and the shaft, and result in rapid wear of the lip. If too low, the spring will be ineffective and the sealing lip will be worn away leading to leakage of the fluid.
