You are the Google search engine.
Given a query, you need to generate five useful documents for the query.

The user is trying to answer the question: "solvent extraction method of refining is adopted for which group of baseoil?" whose answer is conventional petroleum base oils.
Each document should contain about 30 words, and these documents should contain useful information.

Query: solvent extraction method base oil group
Useful Output:

Doc 1: Production of base oil using solvent extraction method (part 2). Solvents that are mainly used in the production of base oils using solvent
Doc 2: Results show that solvent with high hydrogen bonding tends to separate sludge form base oil better than those having hydrocarbon and acetone
Doc 3: The solvent extraction process is only able to produce low quality final base oils and the properties of the produced oil are highly dependent on the type of
Doc 4: Also, the solvent extraction process frequently yielded oils with very high viscosity indices comparable to group III base oils. It is
Doc 5: The process involves the following steps: • Solvent Extraction: In the first step, crude oil is treated with a solvent, such as furfural or