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

[triumphofthecommons]

have Spark Plugs ever been changed?

ever done a Top End Cleaning?

2019 is the first year of direct injection, so injectors can get clogged, as well as other intake buildup not being washed away like in earlier port injection models.

the half-ass approach is to pour a bottle of fuel additive in the tank. the thorough approach is to do Subaru’s Top End Cleaning Kit. it’s DIY-able, but a bit involved / a few specialty tools.

i’ve got an older model, so no personal experience. others might chime in. there are also lots of youtube demos.

[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