For several years, Shell owned the Texaco name and marketed oil and gas under both names (the lubricants company was called Equilon). On January 1, 2002, Chevron took over the Texaco name, but with many provisions for Shell to continue doing business under the Texaco name concurrently with Chevron for a period of several months. For lubes in particular, Shell had the right to market Texaco-branded products until last summer. Shell pretty quickly quit making Texaco-branded lubes other than Havoline, which they produced right up to the end of their contract provision (last summer). Toward the end of their provisional period, Shell sold Havoline at ridiculously low prices, which hurt the brand's reputation somewhat. Equilon Havoline stayed on store shelves for quite awhile, and is probably still hanging around a few places. ChevronTexaco (CTX) has been producing and marketing Texaco lubricants (including Havoline) since January 2002. CTX is promoting Texaco lubricants, particularly Havoline, and will continue to produce Texaco lubes into the foreseeable future.
Fuel is another matter. I'm not as familiar with the fuel situation, but Shell has continued to market Texaco-branded fuels and intended to convert all existing Texaco outlets to Shell by the summer of last year, to remove Texaco's name from the market as much as possible. They weren't 100% successful. On July 1, 2004 ChevronTexaco will begin marketing fuel under the Texaco name and you will begin to notice many more Texaco fuel outlets in areas where the brand recognition is strong (mainly southeastern states).
If you're curious about any other aspect of the Shell/Texaco/Chevron relationship, feel free to email me.