I know I'm just preaching to the choir here but I too have an 07 Tahoe 5.3L with this same issue. It first happened to me when I took a road trip from San Diego to Monterey. We stopped in Pismo Beach for the first night to camp on the beach and that next morning I experienced this issue for the first time. Being that I JUST changed the oil the day before we left, I was scared to death I blew a seal or something was majorly wrong, however, after a thorough inspection all I could see was that I was simply down about a quart. I stopped at a local auto parts store and threw one in. About a week after returning to SD, I was down yet another quart and a half. I've batted around all sorts of ideas that could be causing this issue. My truck shows no signs of burning this quantity of oil in that little amount of time for sure, and there certainly isn't any visible leaking. Mine is not burning near the quantity that LILC quoted earlier:
Like when I went on a trip to LA, CA it was a round trip of about 4k miles and I used up about 6 quarts. California dealer added 3 quarts and when I came back they had to add 3 quarts.
In which case I can't believe that truck isn't puking oil out the exhaust.
Anyway, I certainly know that it isn't the sensor because when the warning light comes on, the vehicle is indeed low on oil and needs a top off of at least a quart. I know for sure that it isn't leaking. So what could it be?..
I have found an interesting correlation between when I first noticed this problem and when I started using cheap "off-brand" oil. Since the rising oil prices (and lord knows all of us with our beloved gas guzzling SUV's have felt them) we have all made changes from what we normally would do. For me, I compromised the brand of oil that I would normally have never deviated from. I switched from Castrol Syntec (which I always have used in the past) to the generic O'reilly Auto Parts fully synthetic oil brand.
Is it crazy to think that maybe cheap generic brand oils break down and lose volume faster than name brand oils? It sounds like a crazy theory but since I switched back to Castrol, I haven't had the problem anymore.
If anyone has more knowledge on oils I would love to read your input. I have no idea if I'm on the right track at all with this but for me, my switch back to a better oil has made a noticeable improvement. I do know that all oils have to meet the same SAE standards so it seems that all oils would be relatively in the same ballpark but I would love to hear more from someone with a greater knowledge of oil....
Gsxr out