Sudden drop in gas mileage

TaosXC70 · Post by **TaosXC70** » 26 Dec 2016, 09:50

My '05 XC70 gas mileage suddenly dropped from 18-28 to 12-20. Got one-time codes about MAS and some other fuel system related issues. I canceled them, thinking they'd come back and now I can't remember them. I've done a forum search and not found a definitive process for problem solving. Can someone point me in the right direction? I have 120K miles on the car.

Post by **oragex** » 26 Dec 2016, 12:12

One of the harder questions to answer..

Being sudden, I'd look first into vacuum pipes then sensors. Does the engine pull as before throughout the whole range ? (2000-5000 rpm)

TaosXC70 · Post by **TaosXC70** » 27 Dec 2016, 17:41

It pulls strongly through the range after a momentary lag.

Post by **MadeInJapan** » 28 Dec 2016, 09:19

Check tire pressure too! We just had new tires put on our car and drove 900 miles during this season. What was 21mpg average is now close to 26mpg average... very odd but it seems that the new tires (and correct pressure) made a huge difference. 4 in the car loaded down too!