I have settled my car loan for nearly a year and I didn't receive any release letter from MBB.

I asked if they'll issue anything after I made my last payment. The bank officer said no and just asked me to go to JPJ to get the "BATAL" stamp at the bank ownership claim.

Bank supposedly will help you to get e-batal thing from JPJ. Then they will return your geran together with e-batal acknowledgement.
If they don't do that, you have to do that e-batal thing on your own.

How to do the e-batal thing on my own? Website?

Not sure if can do online. Best is to go to JPJ counter to check with them directly.

Went to JPJ just now and they said the bank hasn't performed the e-Batal thingy. It's nearly one year! Wasted trip!

Call them and make sure they do e-batal before going to JPJ.

Rule 78 is used in most cases but it is a bit complicated for layman to understand.
Here's some real life examples.

I intend to settle both my car loans in Feb 2014 and the bank has given me the following settlement amount if I settle before end Feb.

Car 1
I took a 6 year loan for RM 320k in Dec 2010.
Interest is 2.58%.
Amount outstanding is is RM 185k.
I have paid about 36 installments.
To settle the loan by end Feb, I have to pay about RM 174k - this figure is given by my bank.
The total interest payable is 2.58% x 6 x 320,000 = RM 49,536.
Since my loan is already half way through the interest I should pay should only be RM 24,768.
So this means if there is no penalty for early repayment to settle the loan I should pay only RM 185k less RM 24,768 = RM 160,232.
This means the penalty I am paying for early repayment is RM 13, 768 or equivalent to 20 months interest.

Car 2
I took a 5 year loan of RM 170k for in Oct 2012.
Interest is 2.32%.
Amount outstanding is RM 142.5k.
I have paid about 15 installments.
The bank told me to settle the loan by Feb, I have to pay about RM 133k.
Total interest payable is RM 19,720.
Since my loan so far is 15 months old, the interest I should be paying is RM 4,930.
So if there is no penalty I would have to pay RM 142.5k - RM 14,790 = RM 127,710.
This means the penalty of early repayment is RM 5290 or 16 months interest.

In short penalty for early repayment is high.
But I would still advise you to settle if you can.
Good not to owe banks money. Also makes it earlier to aim for you next car.
But make sure you have at least spare cash equivalent to 3 months of your salary for emergency. 6 months spare cash is best.