Reuters cited CGT union official as saying that the refinery’s diesel output has been reduced by about 10% due to the strike, which started on Monday.
Last month, union sources told the news agency that the company is considering to close one lubricant making unit at the 247,000 barrel per day refinery in order to focus on higher-quality automotive base oils.
A CGT union official said that the majority of the135 base oils workers at the refinery voted for the strike.
The oil production shutdown also reduced the output of distillate hydrocracker at the refinery by 10%.
Reuters quoted CGT union official Thierry Defresne as saying: "This strike is a first step to express our discontent. We are still negotiating with management.
"After a month of dialogue with management, we will consider whether to extend the strike to other units of the refinery in January."
More than €1bn ($1.2b) has been invested by Total over the last three years on the Gonfreville plant.
