See below is long term oil tests of mobil1 vs amsoil,
keypoint is the wear metals at 9k miles were 50% less with amsoil.
I only use amsoil in my primary car, the two other family accords will
run motorcraft 5-20 and/or amsoil.
For your oil use factory recommendation 5-20 for R-18.
Honda will have sized the rod and main bearing clearances for
this oil. Slowing the flow rate through these bearings with a
thicker oil is not helping anything.
The motorcraft 5-20 synthetic blend is a very good oil at $2.
Top Artic is identical. These are made by Phillips Connoco.
Sometimes when I'm feeling cheap I'll mix 2 quarts of amsoil in
with the motorcraft.
I am using K&N filter HP-1010 part. I get them at
AJUSA.com, free shipping. I also get Denso for the accords.
I read an oil filter test, the K&N and Mobil1 filters are made
by champion. Heaviest construction and best synthetic
media. Although almost identical, K&N media is a little different
and flows more where Mobil 1 is going
for highest filtration. An
important feature is the cold flow rate, the other is filtration.
Another is the bypass valves. Some valves are situated where
they will dump the dirty side into the engine. I think purolator was
one of those types.
K&N and Mobil1 were the top filters, there are other good ones, like Wix
and NAPA Gold.
Denso is paper filter.
If in doubt, pick up and feel the weight of a filter.
The good ones are heavier.
http://neptune.spacebears.com/cars/s.../oil-life.html
http://neptune.spacebears.com/cars/stories/mobil1.html
http://neptune.spacebears.com/cars/stories/amsoil.html