Hi, I have a 2011 Subaru Tribeca with 100k miles and for the past month I've noticed the gas mileage decreased. It as doing 13.4L/100km and now it's doing 15.6L/100km.
I don't see any performance issues, the only thing we are doing differently is using more air conditioning thanks to summer.
Could it be the air conditioning alone doing that? What could be other causes?
Thanks.
When is the last time things like spark plugs, air filter, and fuel filter were changed?
Well, air filter last year, but I've never changed spark plugs nor fuel filter, I've bought the car used.
Might well be time for those items to be replaced.
Replacing the fuel filter is a real pain in the rear end. The fuel filter is built-in inside the fuel pump. It's worse than replacing the spark plugs of the same boxer engine car.
At 100K miles the spark plugs pretty much have to be due for replacement if they're original. The fuel filter is not really likely to affect gas mileage. More likely it would starve the engine of fuel if it plugs up and maybe start killing the fuel pump due to excessive restriction. Check the recommended maintenance interval. Given the location it is hopefully a long-lived part but it can't last forever.
What type of traffic (road conditions) are you driving in? Your numbers sound like big city, stop & go traffic.
If that’s highway numbers, there’s something wrong.. I’d start with the basics like Chuck mentioned, also check your cold tyre pressures.
AC can decrease your mpg between 1-4 mpg, depends on the conditions.
Anything that puts an extra load on that small engine will decrease the mileage.
You may also wanna try cleaning your fuel injectors. Or maybe your throttle body is clogged a little bit.
