2018 Honda Civic 1.5T — what oil weight are you running?

Stick with 0W-20 full synthetic. The 1.5T has tight tolerances and the turbo needs that flow at startup. I run Mobil 1 0W-20 in mine year-round in Arizona and it's been flawless at 85k miles.

Honda engineer here (retired). The 0W-20 spec isn't just a suggestion — the variable timing system and turbo bearing clearances are designed around that viscosity. Going thicker can cause oil starvation to the turbo on cold starts and may trigger the fuel dilution issue these engines are known for. Stay with 0W-20 and change every 5k.

I switched to Pennzoil Ultra Platinum 0W-20 from the dealer bulk oil and my fuel economy went up about 1 mpg. Probably placebo but the engine sounds smoother too. Don't overthink it — 0W-20 full synthetic, change at 5,000 miles, you're good.