AUTOS

Major Upgrade for GM’s Saturn Plant: General Motors Corp.’s Saturn unit said it will invest $48 million in equipment upgrades and expansion at its Spring Hill, Tenn., plant for 1993-model production. Saturn Corp. also said that it will close the Spring Hill plant July 20 for two weeks to change to 1993-model production, slated to start Aug. 3. GM’s other North American vehicle assembly plants will also be closed for those two weeks as part of an annual vacation shutdown to reduce costs. About half of the $48 million will cover a new carbon absorption system for Saturn’s paint operation.