PetroRabigh has discovered methyl tertiary butyl ether (MTBE) in Rabigh naphtha, a grade used specifically for cracking in petrochemical plants. About 200,000 tons of Rabigh-grade naphtha contains a high amount of the gasoline-additive MTBE- more than eight times the permissible MTBE levels in open-spec grade. This has created a degree of scare in the markets as term lifters who are unable to use this grade of naphtha will be compelled to scuttle for cargoes to fill the possible naphtha shortage as petrochemical feedstock. Since PetroRabigh does not produce MTBE, or use it at any stage in the production process, the company will have to conduct a technical analysis to identify the source. The MTBE-stained naphtha is coming at a time when crackers are running at full capacity and when the West-East arbitrage window is technically shut after 1.2 mln tons of Western naphtha were booked for May-July arrival.