So I just finished replacing the valve cover gaskets and plug seals on the 2004 5VZFE Taco.
I've been using Rotella T6 on about a 10-15K change schedule with a Toyota oil filter.
My daily driving is 25 mins highway and about 40 mixed stop and go (traffic AM, vs PM) for 20 miles each way.
Pulled the covers and there's quite a bit of varnish and a bit of sludge, the PCV needed cleaning, but the hoses were still good
and the intake port was clear, so it was breathing, but not as well as it should obviously.
I had a '95 that totally sludged up, but that year had a problem with the airflow.
Obviously need to start changing oil more often, but is the Rotella Gas Truck a better choice now?
Looking for more detergent action, seems like the test results show higher additive levels for that over T6.
Can faces look OK and it does have a negative crankcase pressure (put saran wrap over oil fill port and it was getting pulled down pretty well.)