Project RS

[WRXtranceformed]

yeah i was surprised. i think good oil isn't the be-all-end-all to keep a car running well, but i'm always going to pay a bit more and drive it hard while being worry free

there's actually a lot of conversation in the Colorado / Canyon community (that I think was fueled by some documentation from GM) that high quality oil is a huge factor in reducing the amount of coking / buildup on the intake valves in GDI motors. Installing a catch can like I did seems to be the best course of action to reduce most of it, but good oil is cheap insurance if you care about your vehicles imo

How? Oil in the PCV system being deposited on the valves?

Yeah basically. From what I understand in my non-engineering brain in older non-GDI engines there was a little bit of fuel that washed up on the upper parts of the intake runners. This kept them pretty clean and prevented coking from the suspended oil in the air in the PCV system from just baking on. This fuel wash doesn't happen in newer GDI engines (this I think first got identified in the Audi community actually with their first GDI engines) so it bakes on into crazy hard deposits that cause performance issues, worse fuel mileage and at worst has led to bent valves and big chunks of that stuff breaking off and ending up in the engine:



Some shops actually use disassembly and walnut blasting at different mileage intervals to address it. It is supposedly bad news to use solvent based cleaning as it doesnt work well and can lead to the aforementioned abrasives in the engine:




Bad coking has been documented in the GM world in as little as 10-12k miles