quietspark

I couldn't make sense of this thread... until TheDrip wrote his post. TheDrip likely pegged it. Driving style makes a huge difference in mpg. Having passengers lower a car and thus have noticeably better aero seems really unlikely.

Small engine in a small car. There isn't a logical correlation that a small engine in a small car won't last. Like you, I know of high mileage small cars. In fact, I can think of more high mileage examples of smaller cars than big ones.

Steve, congrats on finding that amazing deal. LS manual I presume? At that price I'd be happy to find some "LT2-ish" aftermarket options if I wanted any upgrades. When the dealer gets their Spark shipment in, how do they advertise the "Spark sale"?

Thermal insulation is different from acoustic insulation. Putting multiple layers of any product down may make it difficult (too thick) to put the carpet back neatly. If you're going to go to the time & trouble of taking up the carpet, an actual acoustic insulation product makes sense. Dynamat or one of their competitors.