FC of Isuzu 10W is average of 6kms/ltr. Make sure you keep track of their FC to see if merong nagnanakaw ng fuel. Best to have someone ride shotgun and monitor actual performance. Palagyan mo rin padlock yung mga gas tanks if wala pa. Minsan daptat may mag-check na sumama sa kanila habang nagpapafulltank sila para makita mo kung tama nilalagay ng gas boy. Nangyari na sa amin na may collusion yung gas boy at driver ng truck. Kulang yung diesel fuel na actual na kinarga tapos yung sobra ibebenta ng gas by pa rin tapos hahatian niya driver. Mga 10 liters usually yan para tig-200 sila at least.
Do a table wherein you can post actual dates of Change Oil Interval (COI) per truck but again make sure the odo is working and make a monthly test first. Then you can already predict the 5,000kms or 6 months max COI.
Same goes for the tires useful life. Dapat consistent at kapag mabilis mapudpod, they better have an explanation. Kasi kung misaligned or may problem dapat sinabi agad para naremedyuhan. Better have a policy na kapag hindi katangggap-tanggap explanation, may charge/penalty sila. It's up to you.
Keep a record of all the maintenance done on a per truck basis and the parts bought for the repair for easier consolidation and review later on. Once in a while, talk to you suking auto shop (do you have one wherein you have a line of credit?)about prices. Mahirap na.