Any point in extending OCI on sludge-prone engine?

[byez]

I own a 03 Highlander V6 1MZ-FE that was just bought used with 85,000 km. I looked over the maintenance records and it had oil changes done at the dealership with 8000km to 15000km OCI's. I plan on doing a flush with Amsoil engine flush after which I will be using Formula Shell Synthetic Blend with Napa Gold filters.

I drive about three thousand km a month and the winters here in Edmonton are quite cold. Around 1000 km a month are highway, the rest of the km's are short trips around the city.

The owner's manual recommends 8000km OCI's. If I plan on keeping this vehicle for at least 300,000 km's, what OCI should I follow? 5000km vs. 8000km?

Thanks

 

[Curious Kid]

Changing a little sooner (5km as you say), sounds like cheap insurance to help ward off such issue. Without oil analysis trending for your service implementation and area, this might not be required.?. Why not use a full synthetic over the winter months to further aide flow and lesson some potential aggressors for sludge (or so marketing leads one to think)?

How do things look through the fill hole/dipstick/oil and filter view? With any "flush" or such, I feel a sense of caution is warranted - I'd change the filter prior to it's use, and keep the OCI short for a few there after (likely more in suspension for the oil's adds and filter to manage. If clean-up is rather sudden, pick-up tube screens might become restricted, leading to poor lubrication issues. Have you removed the pan to have a look at things?

Take care.

 

[byez]

Can't see much through the fill cap but I can see some dark discoloring, nothing major. I actually know the last owner and it was kept in decent condition, I'm just a little worried that the engine might have a little buildup from some extended oci's on dealership oil.