loosing oil 5.4 motor

I have a 2004 superduty van with the 5.4 motor and 85000 miles. It is constantly running low on oil. :headshake It does not smoke on start up, exhaust colour is not blue or black. Tail pipe is clean. There is no oil leak marks on the motor or driveway. I am losing about 1 liter of oil every 800 miles. I am using the recommended 5w20 oil, in the synthetic form. Rad fluid is good and no discolouration, oil colour is fine also, so I don't think its a head gasket. I think that it is being burned off. How can I tell if something worn in the motor and passing oil? What else should I check? Do these motors have oil issues? This is my work truck and I can not afford to have it down. Thanks in advance.:confused: :confused:

I would check around the intake clean the PCV valve and check for something in the intake sucking oil and burning. I would think valve stem seals but this would be noticeable at morning start up.

Thanks, I will replace the pvc valve . I never changed it since I got the truck, some 20,000 miles. The motor looks clean, no evidence of oil leaking.:redface:

Is there a pvc valve on a 5.4? My parts guy says he has no listing for it. Does any one have any part number? Thanks, Nuts.:runaround:

I had a 1997 Ford F-150 with a 5.4L and I thought it had one. I wrecked it about 5 years ago. I'm not sure call Ford parts department if they have one get a part number.