When you’re trading Oil on the MT4 platform, if you hold a position over the monthly expiration date of the futures contract that price is based on, you will encounter a rollover. If you do not wish for your position to be rolled over, then you should close your position beforehand.
This is because Oil is a futures contract which has a set expiration date. If you want to continue to hold your position over the expiration date, the old position must be closed as the contract expires, and a new one opened on the new futures contract.
For a 10 barrel CL-OIL trade, at a price of $98.50 and a difference between monthly contracts of +50 Pips ($0.50), the calculations are as follows:
Long Position: (10 x -0.50) + (-0.04 x 10) + ((10 x 98.50 x -0.002 x 1)/360) = -$5.41
Short Position: (10 x +0.50) + (-0.04 x 10) + ((10 x 98.50 x -0.002 x 1)/360) = +$4.59
All Oil rollover adjustments are calculated in the currency that the instrument is denominated in. If your account is denominated in another currency, your account will be converted at the current market rate.