Salary of OMG officer will be higher than that of DMG if DMG officer is posted at field as asstt. commisioner. DMG officers dont get conveyance allowance. OMG officers get it. a Living example:

At federal Secretariat, OMG officers from 37th CTP get 44 thousands. While DMG officers of the same batch get 40th thousands.. (4 thousands extra for OMG officers for not having car)
But But But..In certain posts, like S.O general and in certain ministries like IT, n CADD etc there are cars for certain S.Os. Here Despite the fact they have car, no conveyance allowances are deducted.

FSP,OMG Audit n accounts, postal, CTG,MLCG, Info, railway, DMG, has same salary..But if DMG or postal group or MLCG officer is posted at field , he/she gets 5 thousands deducted from salaries.

FBR has especial allowance...So has PSP.hence their salary is higher. Finance division has moved a case against this discrepancy in salaries.

But there are OMG officers posted outside secretariat , they get double salary , more than a PSP and IRS/Custom officer.( refer to my Thread on" Deputations of OMG officers")