To flush or not to flush
 

I have a 2007 E320 Bluetec which I bought a few months ago. It has 115,000 miles on it. I was going to book an appointment at a transmission shop to flush and fill the transmission but the man I spoke to said to leave it alone. While I see both sides I feel that at some point new fluid should replace the old. Thoughts please.

I would be guided by your owner's manual. The manual was written by the Germans who produced your car. They know what is and what is not necessary. What does your owner's manual say?

Transmission man doesn't want to be blamed when the transmissions fail. The pilot bushings/connector and the conductor plates are known to go on this model, but not that common. Fluid change is every 40k so you should go ahead and do it and change the connector.

https://www.fcpeuro.com/products/mer...tor-2035400053

Fluid is ATF 134 and you can get it at a shell distributor. About $60 for a case of 12 quarts. Site below just list distributor headquarters, check each distributor for individual locations.

https://www.shell.us/business-custom...r-locator.html

That transmission shop guy has no idea what he's talking about. Go to an independent shop specializing in Mercedes, they'll recommend and get it done for you.

Tough question. There is a risk that any potential, looming issues from lack of scheduled maintenance (and normal wear and tear) will surface with new oil. If it's shifting ok now, maybe leave it alone. At some point the internals will wear out regardless.

That's assuming the fluid was never changed. It might have been changed if he ever looked up the VMI. My standard advice is to change the fluid. You might not want to do a machine flush, but a pan drop and filter change should be ok. If it dies soon afterwards, it was going to die anyway. And if it doesn't, you may have extended the life of the transmission. I believe it was originally called a lifetime fluid but then they later changed their mind and did the 39k recommendation. It may already have been changed a couple of times too. If you notice any odd shifting, replacing the pilot bushing/connector sometimes helps with that too.

Valid point. No dip stick so checking the fluid is difficult but it can be done. The OP doesn't mention if he got any of the seller's service records or whether he is experiencing any trans problems currently.

So, in the absence of knowing, or paying to find out, whether the ATF is dirty/burnt or has ever been changed, and with 115K already the clock I tend to agree with the tech he initally talked to. Even if the fluid has been changed previously (I'm inclined to think it hasn't in the absence of service records), it may not extend the life of the transmission substantially. Coin flip.

In any event, I'm not a flush fan either. I prefer to drop the pan and replace the gasket and filter, even though it doesn't replace all the trans oil.