Maintenance and Fluid Information for 2006 GMC W3500 Forward Isuzu 4HK1
For the 2006 GMC W3500 Forward Isuzu 4HK1, you will find 15W-40 and 5W-40 in the engine-oil listings. The matching product listings include Heavy-Duty Synthetic Diesel Oil 15W-40, Heavy-Duty Synthetic Diesel Oil 5W-40, Signature Series Max-Duty Synthetic Diesel Oil 15W-40. Those are product matches, not proof that every listed oil meets every requirement for this engine. Check the manufacturer’s oil specification before choosing one.
What oil weight does my 2006 GMC W3500 Forward Isuzu 4HK1 take?
The engine-oil viscosities listed for this vehicle are 15W-40, 5W-40.
How often should I change the oil in my 2006 GMC W3500 Forward Isuzu 4HK1?
Use the manufacturer’s maintenance schedule for this engine and operating conditions. The available application data does not establish an exact oil-change interval.

