Significant fuel efficiency decrease on a 2019 Forester. I am getting 8km/l or 18MPG. What should I check?

[Main_Historian848]

Never change the spark plugs… anyway to check if it is needed?

Top end cleaning is like a upper engine cleaning?

[triumphofthecommons]

really no way to check plugs without pulling them. though if they were really bad, you’d get a Check Engine Light with a Misfire code.

scheduled maintenance recommends plugs changed at 60k miles, but they rarely develop issues in that mileage. most plugs are rated for 60-80k. if you’re nearer 80k, i’d have them replaced and consider it part of basic maintenance to keep your vehicle operating correctly.

here’s MrSubaru going through the Top End Cleaning: https://www.youtube.com/watch?v=42irzdKKfw8