Regularly replace the fluid and filterVarious liquids throughout an engine help reduce friction between moving parts, reduce heat buildup, and preserve crucial components from wearing too quickly. Transmission fluid is vital in ensuring healthy vehicle performance, but it can become less effective due to oxidation over the course of as few as 37,000 miles. Oxidation transforms the fluid from its normal red color to something much darker, indicating it can no longer properly do its job.The transmission filter is also something to check routinely, as it aims to catch unwanted particles in the fluid before they reach critical areas. As your vehicle's miles creep up, the fluid meant to help preserve the transmission can become filled with metal shavings, dirt, and other unwanted debris. Fortunately, a filter is in place to help stop these particles from getting inside the transmission, but it can become clogged and need to be replaced.