What are the ways to reduce car's engine noise and changing the engine sound besides adding insulation?

http://www.shell.com.au/products-services/...diesel-hx5.html

how exactly? perhaps less friction, better film strength reduces/prevents engine parts knocking against each other and such force is then transferred towards your engine > engine mounting which are supposed to absorb them and if they are worn/bad condition then it gets transferred to you

if they are bollocks people from the motorsport scene would just stick with shell/castrol/mobil/petronas mainstream oils.

but... that is not the case. they do help, and there are dynos around that proven that it does increases hp. or even videos recordings on engine using different x/y/z brands/models of engine oil.

that's also why people still buy engine oil such as motul's 300v even when the engine oil is priced at really retarded/insane pricing.

granted, this is all ASSUMING the engine didn't have fundamental engine problems like what you said in your post. my point is that when there are 2 same engines without any engine problems running on different oil there will be differences and some may be good on NVH while others may even make it worse (i know for a fact torco EO such as the SR-1 has really shit idle/low RPM noise)