The Royal Dutch Shell Group will purchase Pennzoil-Quaker State Co, the largest motor oil manufacturer in the country. Shell will pay $1.8 billion for Pennzoil, which is also the parent organization of more than 2,000 Jiffy Lube oil change centers across the country. Pennzoil-Quaker State and Royal Dutch Shell are based in Houston, where the combined companies employ roughly 8,200 people. According to Shell, the Pennzoil and Quaker State brands will survive the deal, but about 15 percent of the workforce of the companies will lose their jobs in the merger.