[HuffAZ]

Bought a used 2011 M6 with 4cyl. with 140K miles. Owner had records for frequent oil changes but nothing for transmission service. Most likely because she followed owners manual for maintenance which doesn't show anything for transmission...but thats another debate!

Vehicle's high mileage is due to frequent highway trips 125 miles each way almost daily. I've had several mechanics give differing views on whether to flush or to drain/fill or even one Mazda dealer who said leave it alone with that high of mileage. Many of the more reputable shops will not flush, only drain/fill. Looking to see if there is consensus here from knowledgeable folks. My inclination is to drain/fill, then repeat early after a few 1000 miles. With 140K on it the fluid is dirty. So whats the best method to get it in good shape?

 

[DrFeelGood]

Bought a used 2011 M6 with 4cyl. with 140K miles. Owner had records for frequent oil changes but nothing for transmission service. Most likely because she followed owners manual for maintenance which doesn't show anything for transmission...but thats another debate!

Vehicle's high mileage is due to frequent highway trips 125 miles each way almost daily. I've had several mechanics give differing views on whether to flush or to drain/fill or even one Mazda dealer who said leave it alone with that high of mileage. Many of the more reputable shops will not flush, only drain/fill. Looking to see if there is consensus here from knowledgeable folks. My inclination is to drain/fill, then repeat early after a few 1000 miles. With 140K on it the fluid is dirty. So whats the best method to get it in good shape?

I would do 3 rounds of draining and refilling. DO NOT FLUSH.
Drain the fluid into a container you can measure with. Fill the transmission with the same amount. Start the car and select all gears while engine running running. Turn off engine and repeat the process two more times. It will all work best if the fluid is hot when you start.
I would probably repeat the process (3x) every 60,000mi
Some folks do a drain and refill (1x) every 10,000
Does your existing fluid smell burnt? Whats the color?
Happy Wrenching

 

[MilR]

DO NOT FLUSH ! It loosens the debris resulting in transmission slipping. Just drain and refill with synthetic Dex 6.