I have a 2008 T&C with 135K. Apparently the factory recommended oil is 5w20. Should I be using something thicker like 10w30 for the mileage. I live in Pennsylvania and it's pretty cold here right now.

 

NO, If your user name is as implied, you and I are both from the "Old School" of thought. Stay with the recommended weight, but purchase the high mileage formula type formulation of the brand you have been using. I also am from similar weather area in Western NY!
Do try and stay warm!

 

Indeed stick to advised viscosity but use full synth oil.
Depending on your usage of the vehicle you can adjust your oil change interval to every 13K-15K miles.
Most old school drivers (especially Americans) use very, very short oil change interfals based on experiences with "old school" oils, but oil technology has come a long way since last century

 

My thought was a little thicker oil would compensate for the wear of 135K miles. The car burns no oil and has been maintained perfectly since new.

 

135K isn't that much in my opinion and when there is little or no oil use also no reason for using "thicker" oil. Even when there would be some "wear" in the engine I highly doubt if changing oil viscosity would do much good.
A good brand full synth oil with high tech additives will protect as good as possible imho.

Btw, I am at 225K miles now and my engine doesn't use oil either which I find very remarkable... The VM diesels are pretty indestructible.

 

I agree with what Vmaxxer says. Stick with the factory viscosity, use a good quality synthetic oil and change it on a regular basis. I do mine every 4 months or 4000 miles, whichever comes first. I've done this with all of my vehicles and have had several top 300,000 with easy.

 

If you use higher viscosity oil than advised by manuf. expect your fuel consumption reading to go south. With you looking after the vehicle, 135,000 miles covered is nothing.
Leedsman.