I just picked up a 300TE and at the last oil change the oil change place used 15W-40. This seems way too thick for a Michigan winter and I am planning on chaning it to a synthetic 5W-30 but before I do, is there something I'm not considering? Does a '93 300TE require high viscosity oil for some reason?

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1987 300SDL 167k
1992 Volvo 740 140k
1990 Volvo 740 250k
1989 Volvo 240 269k

Anyone want to trade an old Volvo for an '87 300sdl?