Mileage drop

[Murphy]

ok, i now some post have been like this before, but i searched and couldnt find any similar to my problem

my car used to get 25-26mpg on the daily commute (about 65%highway/35city) and on long trips that were straight highway i got 30mpg usually, sometimes more.
but in the past several months, i can not get over 21mpg, i got 27mpg on straight highway. the last time i got over 21mpg was when it snowed an i had been doing donuts in parking lots and sliding through corners, i got 24mpg on that tank.

the oil is new, pcv is new, airfilter is clean, fuel filter is new, all tires are at 35psi and new, i even ran Seafoam through a vacuum line. all except Seafoam was done last summer.
i think if it was the O2 my mileage would be much worse

i just cant figure it out

[jefferson]

I would think about the coolant temp sensor and make sure you don't have a brake dragging.

Jeff

[Herm99]

last time the plugs were changed? wires? How old is the O2 sensor, even if its not throwing a code they become tired over age, their values drop with mileage, might be time to replace it..and use oem, none of the splice in universal crap.

[Legacy777]

Has your gas changed?

I ask because a lot of states/cities are going towards E10 blend gasoline. You'll see a hit in mileage with E10 compared to straight gasoline.

[Murphy]

i checked my plugs today, they were in great shape, less than a year old. plug wires are about 2 years old. did a pretty much complete tune up last year. the o2 is old, but i hear if that happens than your power will also decrease, but there has been no change in power.

i forgot about that E10, i got gas this morning but i never thought to look at it. i know there is alteast one station in town that has E10, but i am not sure if it is every station or not because i never think about looking at it when i am there.

i will do a check on the temp sensor tomorrow, i think that could be the problem if it turns out that i havent been using E10

thanks for the help everybody