the only reason i ever put in heavier weight oil
was to slow down the leaking in the seals (my 73
dart may god give her peace). higher viscosity
means slower leaks. however, in newer vehicles,
the tolerances are much tighter, heavier oil will
boost your pressure a little, but will reduce the
flow, so theorectically speaking you could be
getting reduced heat and waste transfer and
reduced lubrication.

you should stick with the OE recommended oil
weights. i have a 93 wrangler with 175k and i
still use 5w30 in it. my 89 camry has 275k and i
use the same oil. this is the same oil we use in
all our cars here at the shop.

No.