I have a 2000 Civic Coupe / 87k mi.

Had the 80k mi. service done about 2 mos ago (@Dealer), and have noticed a marked decrease in my mileage.

Used to get 310-315mi / Tank
(11.9gal tank)
Never drained completely, prob filled up w/ 2gals remaining
~31-32mpg

Now I get ~252mi / Tank
~25-26mpg

I've had this car for 3+ years, never noticed a decrease like this..even in winter. Drive very normally..70% highway..not a speed demon or really hard driver.

Ran a bottle of techron through, and no changes yet.

I've been given all sorts of advice..from plugs, to fuel filter, to thermostat, to vacuum leak.

Anyone offer a more solid diagnosis? Need more info?

Thanks,

PD