2002 Honda Civic LX

Rear main seal leak on my 2002 Honda Civic LX.

Hi Mr. Kilmer, I have a 2002 Civic LX with 100k miles on it. It is leaking oil slowly, a mechanic told me that the leak is from the rear main seal, and is not worth to pull the engine and transmission out to fix it. My question is, my civic take 5W20, can i use a heavier oil like 10w40 to slow the leak? will it damage my engine if i use a heavier oil during winter?

that won't stop it, but AT 205 reseal added into the engine oil may stop it. amazon sells the stuff.