Lifter tick from passenger side bank.

[immortal_suby]

Run some engine oil cleaner in it.
Follow the directions exactly. They usually have you idle the engine for a few minutes and then change the oil immediately.

Cured every ticking subaru I've ever owned.

[svxistentialist]

Mike

There can be a number of different types of "extreme use"

One extreme would be hammering your car at high revs round a circuit. For this extreme you will be traveling at high revs in all gears, and you will need your oil not to break down and suffer heat damage. If this is your extreme, use fully synthetic.

At the other extreme is a rarely used car. This will mean lots of cold starts. Cold starts where the oil does not loosen up and distribute round the engine extremities can mean friction wear on valve guides, piston rings, liners, etc. If this is your extreme then fully synthetic is good, it will retain low viscosity when cold and quickly lubricate moving parts when cold.

For anything in between then semi synthetic or the manufacturer's recommended mineral oil are more than adequate.

Joe