I want to compare two things

[alpacinou]

I want to compare two things. I have searched the internet and apparently I can't use "comparing" and I should use "compared".

My question is, why is "comparing" wrong and "compared" correct?

Comparing with Ford Mustang, this car is cheaper.

 

[jutfrank]

You don't generally need to ask why things are wrong. Just focus on what is right. Here:

Compared to the Ford Mustang, this car is cheap.

I've used the to show that the speaker is referring to a specific Mustang.

Here are a couple more examples for you:

My English is rubbish compared to yours.
This is nothing compared to what we had to go through last time.

 

[5jj]

I would say
either: This car is cheaper than the Ford Mustang,
or: Compared to the Ford Mustang, this car is cheap,

 

[jutfrank]

I would say Compared to the Ford Mustang, this car is cheap,

Me too. I've amended my post accordingly.