Same old, same old . . . . this has happened to me more often than not on my last 8 "new vehicle" purchases . . . . . I just purchased a new 2009 Silverado Crew Cab - 5.3 Flex Fuel, Active Management V8 . . . . I drive the vehicle home from the dealership, let it stand in my level garage all night and take a dip stick reading in the morning . . . . . sure enough, it's becoming predictable . . . . the dip stick reading is almost a full inch above the full mark . . . . and, at the same time, the owners manual warns "not to over fill with oil because it could cause harm to the engine" . . . . . I get under the vehicle and drain out one-half quart . . . . . the dip stick now reads one-fourth inch above the full mark . . . . . I drain another one-fourth quart and now the dip stick reads exactly on the full mark . . . . . . did the dealer over fill or is 6 quarts (oil capacity for my engine as shown in the owners manual) too much? After 2800 miles, I change the oil myself (including filter) and fill with 5.25 quarts instead of the owners manual 6 quart specification . . . . . I let the truck stand all night and in the morning the dip stick reads exactly on the full mark. So what do I do? . . . . From this point on, do I over fill with the owners manual specified 6 quarts or do I use my own determined 5.25 quarts (with filter) that results in the exact "full" reading on the dip stick . . . . . No one seems to be able to give me a definitive answer . . . . dealers and customer service technicians have, at times, given me contradicting answers . . . . some say put in the owners manual specified amount regardless of dip stick reading . . . . . others say put in less than the amount specified and slowly add additional until the "full" reading on the dipstick is achieved (5.25 quarts with factory filter) . . . . . I have had this same confusion on my new vehicle purchases over the last 12 years . . . 3 new suburbans, 3 Toyota Tacomas and a Honda Fit . . . . why do these inaccuracies exist with something so simple and critical as an oil change???

 

My theory on this subject is that there could be two types of oil filters in the equation. A deeper or less dense aftermarket filter and a factory filter with the same part number. In my theory, the oil fill is based on the higher capacity of the deeper filter rather than the smaller factory filter, thus appearing overfilled.
The dipstick is correct and it will not hurt anything to run the oil fill at the level the dipstick prescribes. It will also not hurt anything to run the oil level at the level it was before. Overfilling would be a quart more than prescribed. Put 7 instead of 6, and the oil pump will be at risk.
This is as stated, my theory.

My Blazer is the same way. The prescribed level tends to be a half-inch above the fill zone.

I'm sure someone can confirm this theory for me.

 

I am sure if it was overfilled the oil pressure would sky-rocket on the guage as well. Did you happen to monitor the guage during the full & overfull times?

Right EB,this would be a good one for the ASE guys to confirm, I fill it to the dip stick too, not by the manual. I understand its not a critical thing, just curious.

 

good idea with the oil filter guage . . . . . I do monitor it on a regular basis and did not notice any high pressure during the period when it had the dealer/factory full 6 quart amount

 

Oil density does vary with the temperature too so that could be a factor.

 

Well common physics says that the hotter something is , it gets bigger/expansion. If he said he checked it cold in the morning, commom sense tells me its shrunk the most it can. Unless oil works different. Good point though Or it could be how quick you fill it back up, not letting the old oil drip for 20 min, I can sometimes get an extra 1/3 quart after it drips. I never rush an oil change.

 

With a new vehicle under warranty, I would do as the OP did, and fill to the "full" mark.How would anyone like to explain to the warranty department they purposely overfilled the engine?

If the dipstick is so inaccurate it causes damage to the engine, that's what warranties and warranty departments are for...

 

I assume that perhaps GM corporate office determines the "full mark" based upon the amount of oil settling back into the crankcase within 5 minutes of turning the engine off . . . . and not letting the car cool down overnight as I did before checking the reading . . . . however, even cooled down overnight should not result in a reading a "full inch" over the full mark . . . . . dealership service technicians always seem to be somewhat "baffled" when describing the situation . . . . but most tell me to put the recommended amount in it regardless of dip stick level . . . . . (not just GM, but also on my past Tacomas and Hondas) . . . . . when calling GM (or any other corporate car manufacturer headquarters) and requesting additional guidance, I usually and eventually become connected to an advisor who tells me that actual dip stick reading "trumps" all other written literature . . . . . it just doesn't make me feel at ease that there is so much uncertainty out there . . . . I guess I'll have to conclude that replacing the oil until the full mark is reached is the best approach . . . I really do appreciate the advise of all who responded on the forum . . . . thanks

 

Your welcome! , thats what were all here for

 

The reason it reads over full is because you are checking it after letting it sitt all night. That gives time for almost all the oil to settle back down in the pan. You are suposed to start the engine let the oil circulate then turn it off wait a few seconds and check the oil. All of the 5.3 that I have ever worked on take 6 quarts. If you only put in 5.25 you ARE under filled