SENTENCE WITH COMPARISON

1. something is similar A=B

Our car is as fast as Peter's car.

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2. something is not similar A><B

a) Use not as ... as (to say that something is not similar)
John's car is not as fast as our car. (A><B)
b) Use than (to say that something is bigger or smaller)
Our car is faster than John's car. (A>B)
John's car is slower than our car. (A<B)

NOTE!

Peter is taller than me. (informal)
Peter is taller than I am. (formal)
Max is as tall as me. (informal)
Max is as tall as I am. (formal)
Do not mix up than with then.
see: then or than - Confusing words