Is dexron 3 compatible with dexron 6?

Yes, Dexron III is generally compatible with Dexron VI. Dexron VI is an upgraded version with improved properties, and it can be mixed with Dexron III without issues, although it's always best to use the recommended fluid for optimal performance. However, for the best results, particularly in high-performance or high-temperature applications, it is advisable to fully replace the old fluid with Dexron VI. Always check the manufacturer's specifications for your vehicle to ensure compatibility.