UPDATE 2-Shell SF Bay refinery shut Alky unit Monday-sources

(Adds Shell comment)

HOUSTON, July 30 (Reuters) - Shell Oil Co's RDSa.L 165,000 barrel per day San Francisco Bay-area refinery in Martinez, California, shut an alkylation unit on Monday for unplanned work, sources familiar with refinery operations said on Wednesday.

Since Monday, San Francisco Bay wholesale gasoline has been running between 2 cents and 3 cents over prices in the Los Angeles market, which are normally higher, on rumors of work at a refinery.

A Shell spokeswoman said the company does not discuss day to day operations.

An alkylation unit uses refinery uses acid to convert refining petrochemical byproducts to gasoline octane boosters. (Reporting by Erwin Seba; Editing by Andre Grenon)