Why is my Suzuki XL 7 using too much fuel
I have a 2003 Suzuki XL7. It has been a great car so far. I had absolutely no issues with it all. However, last month I took it to Firestone for an oil change and the day after while driving the engine started knocking, I mean it sounded like a jack hammer and smoking like crazy. So I pulled over and turned the engine off, looked under the engine only to see that the drain plug was missing and all the oil has leaked. Long story short, Firestone came and towed it back to the shop, put in a new plug and added oil. The car sounds and drives good but the fuel consumption went down to 13 or 14 miles a gallon. I replaced one of teh oxygen sensors but the gas mileage did not improve. Wondering what could it be. Is it related to the Firestone incident or was merely a coincident?