He still can memorize something

My mum always tells him not to go to the petrol station everyday
But he has made it routine to the petrol station everyday after going to office
One night Lina found out that the money that he spends is not reasonable
He is given RM 30 everyday, but at the end of the day, there is only a few ringgits in his wallet
Normally he just spend for food only
and it is too much to spend RM 30 plus a meal

light is shedded on the question one day.
When Lina went to a petrol station and the cashier told her
" Uncle will come here everyday. And he will forget to fill the petrol after he has paid the money"
Then a cleaner who heard the conversation in distance added in a curious manner
"Ya, I have also noticed it. I wonder why he can forget it every single day"
Then the young cashier advised Lina not to let him to come alone anymore

My mum was so startled and at the same time feels so hurt inside
because now she knows that the case is deteriorating now

I think that even though he has Alzheimer but he still can recall think that is told to him sometimes
May be after he pays, he recalls that Lina has told him not to fill and so he goes off
or may be he just simply forgets that he hasn't fill as he walks back to his car after making the payment.
whatever it is, it is not a good sign