Volvo D11F Operator's Manual And Maintenance Instructions page 60

56 Maintenance and Service
Chassis Mounted Primary Fuel Filter (Optional)
For priming the fuel system, see "Priming the Fuel System" on page 71.
Replacing Fuel Filters
When draining the fuel filters, collect the waste in a fuel-safe container.
Always dispose of fuel according to Federal or local regulations. Take the
drained fuel and water to a recycle or waste management center.
The filters are an important part of the fuel system. Always replace the filters
at the recommended intervals and use the recommended filter types for the
best engine operation and service life.
Change the fuel filters at every oil change. Drain the primary filter water trap
daily.