Touareg: 2013 V6 TDI
Join Date: Nov 2014
Location: Winnipeg, Canada
Second Vehicle: VW 2
Thanked 54 Times in 52 Posts
All 4 tires need to be within 2mm in diameter of each other and the same brand and model. It is surprising that the dealer would change only 2, as this could cause expensive transmission problems.
As for tread life, I'm assuming you are in the USA and are talking about miles. Remember this is a global forum. Therefore, 40,000 miles is not much. But there are a lot of factors affecting tread life, such as driving style and driving conditions.
I suggest you search the forum for other tire tread life posts. I know this has been discussed a ton in the past.
"Callie" - 2013 Touareg TDI Execline, Cool Silver on Titan black
"Sophie" - 2010 Touareg TDI Highline, Campanella white on Anthracite - sold back to VW
"Celeste" - 2009 Eos 2.0T DSG Lux, Candy white on Anthracite
"Simone" - 2002 Golf GLS TDI, 5 speed, HID projectors
"Rocinante" - 1990 JDM HDJ81 Toyota Landcruiser turbodiesel, 5 speed, RHD