Malay staff at my workplace

I got 1 Malay colleague at my workplace. He is the supervisor, no no no, He WAS the supervisor of all the servicing technician. He works for the company over 8 years already.

Lately, we found out that the diesel bill for his vehicle went up RIDICULOUSLY. $800++ for May.

Our company got 3 vehicles. 2 lorries & 1 van. For our company policy, drivers CANNOT drive the vehicle back but for some special reason (i think maybe he work long enough), he can drive back the van every weekend. Even though we know he drive the van back during weekdays, we didn't say anything to him as we take it as HE KNOWS WHAT HE IS DOING but seems that he is obviously NOT.

Monthly diesel expenses for both lorries about 300 to 400 plus depends on our schedule. How can he use up to 800++ for a van? We question him, but he deny everything! He said sometimes we gave him so many works untuil he have to work OT so he drive back, the van makan minyak, sometimes he goes to see football... bla bla bla...

So, my boss decided to gave him a chance. YOU STILL CAN DRIVE BACK THE VEHICLE, I"LL MONITOR THE METER FOR THE VEHICLE FOR THIS MONTH.

So, I got additional job since 8th June 2009. Record the meter for 3 vehicles every morning.
Mon (8 June 2009) : Lorry A - 104km, Lorry B - 63km, Van - 163km
Tue (9 June 2009) : Lorry A - 79km, Lorry B - 53km, Van - 165km
Wed (10 June 2009) : Lorry A - 73km, Lorry B - 100km, Van - 238km
Thur (11 June 2009) : Lorry A - 81km, Lorry B - 82km, Van - 187km
Fri (12 June 2009) : Lorry A - 73km, Lorry B - 82km, Van - 301km
Sat (13 June 2009) : Lorry A - 37km, Lorry B - 42km, Van - 240km
Please take note that Saturday we only work half day.

Crazy is it? Actually for his vehicle I do special record on my boss request. I record the meter when he came back late evening and again on the next morning so I know how far he travel after in & working time. (W - working time ; O - off work time)
Mon : W - 72km ; O - 91km
Tue : W - 50km ; O - 115km
Wed : W & O - 238km (Didn't manage to record late afternoon because he work OT)
Thur: W - 72km ; O - 115km
Fri : W - 136km ; O - 165km
He really pig head! Your boss already told you we will record your meter everyday & YOU KNOW IT! why are you still so stupid? STOP for a while lar! Really wonder what is in his brain you know? STUPID like hell!
Immediately my boss stop him from driving back the van on Saturday, he still stupidly ask my boss why (he said my boss promise him to observe him for 1 month, now just 1 week)... Walauwei.... Really funny man....
Monday he didn't came for work, we can't contact him also. SURPRISINGLY when I record the meter for the van, it goes up to 240km even though we only work half day on Saturday & the time he came back he already pass us the key.
HE GOT DUPLICATE KEY & use the van even we already ask him NOT TO!
Today is wednesday we still can't find him (neither his family)...