I recently switched my 03' Subaru Forrester X to AMSOIL Series 3000 Synthetic 5W-30 HDD at about 20K miles; this included a crankcase flush before putting in the synthetic.

One thing is for sure, the 2.5L "boxer" engine absolutely destroys conventional 5W-30 after 3000 miles. I tried Lucas stabilizer, it helped a little, but not much. Note I did not have any oil analysis done, just going on how it looked at drain time.

So I asked a mechanic at the dealer garage about this, and he said to try this AMSOIL HDD. After about 2500 miles, the oil looks basically new. Looks like it's going to work out pretty well. I think the engine even runs a little smoother.

So now I'm a satisfied AMSOIL customer and looking at switching my truck to their Series 2000 0W-30. I have about 8K on the truck, so I was getting ready to make the switch to synthetic anyhow. I was thinking about doing AMSOIL bypass kit at the same time.

Thoughts....