Hi there I have an 02 ss and I'm having crappy fuel mileage right now like 13mpg and was wondering does anyone have a list of fuel system components and ways to check them on my own. I wasn't my 22mpg back atleast if not better. I've already replaced the fuel pump so that's as far as I've gotten

 

I'd start with a tune up to include replacing both oxygen sensors. Then if that doesn't clear it up, I'd start replacing sensors. How many miles on your car?

 

she has 220,000. So replace sensors even though engine light isn't on. It was on last week but it was p0128 the thermostat code n I replaced that

 

Well IIRC they don't throw a code unless there's a severe drop in voltage or they stop working all together. If they are off they could cause your car to run richer which could cause your MPGs to drop drastically. A MAF sensor problem could also contribute to this as well. How long has it been since your last tune up and/or O2 sensor replacement? At 220k miles there's several things that I'd venture to say are probably in need of replacement or cleaning all together. LIM gaskets could also be leaking which could put a dampener on your ability to create enough good spark and fueling in your cylinders. Head gaskets leaking could do this as well. The fact you've thrown a temp code could be an indicator of something along these lines. A bad T-stat could also cause your car to run hotter than normal which would call for more fuel to prevent pre-detonation which is also known as KR or knock retard which retards your timing and could also result in more fuel to compensate thus equaling a loss in MPGs as well.

 

Its been about 6 months n it was a major tune up. So there can be a leak in the head gasket even without water on the ground? Wow from the looks of things I gotta shell out some serios cash huh to check everything

 

Well not really, a head gasket leak can be checked by a compression or coolant carbon/pressure check. Both are relatively inexpensive. And yes you can definitely have a head gasket leak and not drop a bit of coolant on the ground. Some could possibly seep out onto the block but would probably be burnt off and evaporated before it could hit the ground. I have seen some cases where you can actually see the rust stain on the block and head where it leaks out and dries.