BUICK PARK AVENUE ENGINE POOR MILEAGE

Hello -- My Buick Park Avenue With A 3.8 Engine Has Sat Idle For A Year. Before I Put It Up It Was Getting 24-27 Mpg On The Highway; Now It...

My Fuel Mileage Has Suddenly Decreased By 10% And Sometimes There Is A Rough Idle Upon Ititial Start Up That Clears Up As Soon As The Engine...

Up Until 2 Months Ago, My Buick Ultra Averaged 29-31 Mpg. Now It Gets 24 Mpg. No Smoke From Tailpipes Is Noticed. Plugs Replaced. Engine...

I Have Very High Miles On My Car Because I Travel A Lot(279564 To Be Exact). Whats The Best Way That I Can Keep My Car Running @ Top...