Most cars use hydraulic valve lifters that rely on oil pressure to maintain a tight clearance between the camshaft and rocker arm. If the pressure isnt right, there is play between the lifters and the rest of the valvetrain, which causes a noticeable tap. Its possible that cold oil at startup may help pump up the lifters, but at normal temperatures the viscosity drops, and may be too thin to correctly work the lifters. As the oil breaks down after a few thousand miles it thickens, which eliminates the noise.
1 Heroin is a highly addictive and rapidly acting opiate (a drug that is derived from opium). 2  Specifically, heroin is produced from morphine, which is a principal component of opium. 3  Opium is a naturally occurring substance that is extracted from the seedpod of the opium poppy. (Generally, the purer the heroin the whiter the color, because variations in color result from the presence of impurities.) In the western United States, most of the heroin available is a solid substance that is black in color. 2  This type of heroin, known as black tar, may be sticky (like tar) or hard to the touch.
Heroin is a pain-killing drug, which is derived from the dried milk of the opium poppy and white crystals. Heroin belongs to a group of drugs known as opiates, other opiates i â¦ ncludemorphine and methadone. Heroin is an addictive opioid substance. 2  Most often, it is injected directly into the user's vein via a needle. 3  Heroin is unlike other drugs such as ecstasy and alcohol in thâ¦. 4  Major Long Term Effects of Heroin Use Every illegal drug has both short-term and long-term effects.