I have a 95 Geo Metro that I inherited two years ago with 89000 miles. It has a 1 liter 3 cylinder engine. When I first got it, I was getting 40 mpg, now two years later, I'm down to 30 mpg. I change the oil every 3000 - 4000 miles and I have replaced the air filter. Spark plugs and wires are next. My check engine light is on and according to AutoZone I have a bad EGR valve but according to Advance I have a bad ground on my computer mod. A new EGR valve is $150 so if the valve is the reason that my milage is down, we are only talking about the equivalent of 1.5 gallons per tank, so I can stand a little less milage and keep the money in my pocket. I am not certain that the EGR valve is the problem.
I have a spread sheet that has the milage and dates of fillups for the past two years so I have watched the milage drop.
Is it just old age or where should I look to try to get back to the blessed 40 mpg?