GST applicable for used cars?

yes gst is applicable in supply of used car... rate of gst is 18 and 12%

As per Notification No. 8/2018, CT ( RATE ) dated 25th January 2018 :

1). Old and Used, PETROL, Liquified Petroleum Gas ( LPG ), or Compressed Natural Gas ( CNG ), driven motor vehicles of engine capacity of 1200 cc or more and of Length 4000 mm :

GST RATE : 18% [ 9% CGST + 9% SGST ].
CHAPTER : 8703

2). Old and used, diesel driven motor vehicles of engine capacity of 1500 cc or more and of length of 4000 mm.

GST RATE : 18% [ 9% CGST + 9% SGST ].
CHAPTER : 8703

3). Old and used motor vehicles of engine capacity
exceeding 1500 cc, popularly known as SPORTS UTILITY VEHICLES (SUVs) including utility vehicles.

Explanation. - For the purposes of this entry, SUV
includes a motor vehicle of length exceeding 4000 mm and having ground clearance of 170 mm. and above.

GST RATE : 18% [ 9% CGST + 9% SGST ].
CHAPTER : 8703

4). All Old and used Vehicles other than those mentioned from S. No. 1 to S.No.3.

GST RATE : 12% [ 6% CGST + 6% SGST ].
CHAPTER : 87

Explanation –For the purposes of this Notification :

(i) in case of a registered person who has claimed depreciation under section 32 of the
Income-Tax Act,1961(43 of 1961) on the said goods, the value that represents the margin
of the supplier shall be the difference between the consideration received for supply of
such goods and the depreciated value of such goods on the date of supply, and where the
margin of such supply is negative, it shall be ignored; and

(ii) in any other case, the value that represents the margin of supplier shall be, the difference
between the selling price and the purchase price and where such margin is negative, it shall be ignored.

Regards.

Your question is not clear. What i understand that is gst applicable on sale of old car?

Yes, GST is applicable

It can be classified in two part.
(i) used car purchased before GST
(ii) used car purchased after GST

Case (i)
Rule 32(5) of cgst act
GST apply on margin @ 12% or 18% as per vehicle cc and SUV
Here margin means difference between sales prices and WDV
If WDV not available then purchase price
If margin comes negative then ignore GST

Case (ii)
As per rule 44 of CGST
Step - 1 :Reduce 5% ITC every quarter. (part of quarter consider as full quarter)
Step - 2 : calculate GST on selling price by applying respective %
You've to pay GST whichever is higher from step - 1 and step - 2