Agreed. Do it every 30k or 2 yrs, so start now so you know it's history. If the fluid is looking very brown and smells, change with the cheapest ATF you can find, use 4 gallons and do it again in 2-3k miles, but use synthetic. The synthetic is not necessary if you change frequently, but will make an old tranny shift smoother. Depends on what you want to spend. Invest in a flush kit, and the money you save will be well spent on better fluid. Even if you go synthetic, still do the flush every 30k or 2 yrs.
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'89 245 sportwagon, destroyed by hit & run driver, RIP. '04 V70 2.5 T Sportwagon, 12k mi and '91 245 5-speed, 209k mi, replaced the '89