Bought an used 2008 Ford Escape Hybrid with 97k miles on it. After drove two weeks, the average MPG is only 32.3. Does it mean the HV batter is not good. How hard is it to switch the HV battery with an used one from junk yard?

Updates:
After I changed the oil, it's getting much better. After 1000 miles driving, it's 35.5MPG now.
I guess my hybrid battery is good：）

 

All depends on the kind of driving you do man.

 

Unlikely, especially if you have AWD. That is about what they get. The best my AWD ever got is about 31 highway at 70mph 35 at 60. The high voltage batteries generally don't fail, the under the hood kinda fail without warning, so it's good to check them regularly. With it being winter I am actually surprised you are getting 32. I get about 22 or less in the winter usually. Lately I only get 24 or 25 summer, but it's not battery related, some kind of intermittent problem that makes the engine run like crap and rev higher.

 

Also I read your other two threads, I would look at your 12v battery as causing issues that you are seeing with the vehicle not starting. A good digital multimeter like a Fluke is nice to have for all things in life. A good true RMS one can be had for under 100 bucks used on ebay. You want one that says true rms. You don't really need to worry about what category it is since you won't be using it industrially. Just make sure you always have you leads in the right place, measuring voltage with the leads in the ammeter secion can cause the fuse to pop or sometimes the meter to explode in your hands (rare, but happens enough to make sure to avoid)

Past that I would invest in a Scan Gauge II, they're really nice to have so you can see what a lot of your major systems are doing. I see a used one on ebay for 115 shipped and you can probable get a used one lower if you look hard enough.

 

I agree with Tyler, 32 is good unless you are an extreme hyper-miler. I'm getting 30 with normal driving and love it. My little SAAB 900 vert. only gets 25 if I'm lucky. I was tickled to death with 30 for a SUV with AWD.
Is it going into EV mode?

 

After I changed the oil, it's getting much better. After 1000 miles driving, it's 35.5MPG now.
I guess my hybrid battery is good：）

 

It's rated for 32 mpg combined so you're fine. And if you're getting 35 mpg then you're really fine. By the way, you'll get lower mpg in the cold season and higher in the warm season. I've had mine go as low as 26 on the highway to as high as 38 in the city if I'm really careful.