Hello every1, went over 70k recently. noticed that my mpg rating has decreased drastically, on a full tank of gas i only did 330 miles of highway driving, the only non stock parts i got are cold air intake and 17 inch rims. what kind of maint should i do on the car at 70k? i was planning to do the engine flush, change the spark plugs, power steering fluid still looks pink, should i mess with it or not?
same goes for the brakes. i also plan to change transmission oil along with the screen.
anything else ?

 

How many highway miles do you typically get on a full tank?

Did the lower gas mileage start right after you added the non-stock parts?

Changing the plugs and plug wires might help. Are you using 5W-30 oil, which I assume is recommended for your Civic?

 

Check your timing. You might consider a new timing belt if it has a lot of years on it even though not miles, i.e. if the car has been used relatively few miles per year.

When you have bigger tires on, the car is actually traveling more miles than the odometer says.

 

its a 2001 LX with 73k miles. do you think its time for the belt?
and no, i had the non stock parts for a while., the only thing is i didnt clean the filter for last 10k
i suspect it might be a problem, but it should not affect it to this degree.
as per mileage, i used to get around 360 miles per tank, now, last time i did only 290.