Sudden decrease in MPG?

[lashk]

2009 Vibe 1.8, 55k miles. Has anyone experienced a sudden decrease in MPG. My car went from 30 mpg to 25 mpg and I can't seem to figure out why. Highway and/or city driving. I checked tire pressure, air filter, etc. I even pulled the VVT and oil control valves and both were clean. Car runs normal so I'm kinda stumped... Any suggestions would be appreciated!

[Caretaker]

I have the '09 1.8 liter automatic and the same thing happened to me. I have 77,000 miles on mine. I had been getting 33 mpg in all suburban driving, until the last 3 months when my mileage dropped to 29 mpg. Nothing earthshaking, but I had not seen a 4 mpg drop in 4 years of ownership. I took my car in to my mechanic only to find out that our PCV valve is buried underneath the intake manifold. As such, I have not had it changed yet. I did have him spray down the mass air flow sensor atop the air box. My mileage has since recovered. While we are getting close to the winter blend crossover which will cut down on mpgs, I certainly can't blame it on that given my troubles started in June. My last mpg calculation was 32.8 mpg, so back to normal. I would advise unscrewing the mass air flow sensor and giving it a good spraying with MAF cleaner to see if that helps at all. I'm not sure what the smart people on this board recommend, but I do realize that I will have to bite the bullet at some point and have my mechanic put in a new PCV. I'm sure they don't last forever.

[lashk]

Hey Caretaker,

That sounds great! I'll plan to do it this weekend. I've cleaned these in the past on other cars but didn't even think of it in this situation. I may even check the one on my Tundra. Thanks again!

[Derf]

Possibly your gas station switched to blended fuel? I noticed out west with 100% gasoline I picked up 2-3mpg, back home it tapered back off with the 10% ethanol blend. Funny thing is the 100% gasoline was cheaper. Agree, many of the posts on this site indicate a slight bump in MPG after cleaning the MAF sensor

[creekhed1]

Did the stations in your area switch to winter blend?

[clownshoes]

They have up here in canuckistan. MPG has dropped significantly.