The Bonneville was purchased last August, and the oil level was fine until I changed the oil in November. I went with Mobil 1 5W-30 synthetic. I don't recall how often I checked the oil, probably only a couple times but in January the low oil light came on the DIC. It ended up down about a quart if I recall, and I just added a quart of regular 10W-30 dino oil that I had in the garage. It was fine again until I changed it again in May. So again I went with synthetic, this time with 10W 30 (I don't remember why I changed). Fast forward to yesterday, the light came on again (bad me, I haven't been checking it). And again it'* down a quart. So again I added a quart of dino oil I had, and I'm going to make sure and monitor the level more close.

I know I've heard of people adding a quart or two of dino oil instead of doing full synthetic. Since this seems to cure the problem, should I just do this from now on, or should I be worried about a potential problem? The block is a bit dirty/oily, but I couldn't find any evidence of leaks, and I don't have any oil spots in the garage either.

Smoking at all on hard accell? Valvestem gaskets could be shot. Id clean as much of the engine off with brake clean and put in some oil dye. Keep and eye on any leakage/seapage with a black light. The dye will show up like a flourescent color (orange, blue, white, depends on brand and type of light) but you should be able to see where its coming from eventually. Try fixing all those. Ive also heard that a lot of engines eat a quart of oil every 2,000 or 2500, just the nature of lubricant being evaped by heat. You also break down things in the oil that would make it use more volume as you drive your car.

No smoking that I've seen. I also remembered I need to check the pcv valve. I don't know if that could be a part of it.

that happens on my dads SE and my moms SSEi, they lose a quart about every 3k

Thats just normal usage, so I've heard. If ya think about it, have any of us ever taken out as much oil as is capacity on an oil change.........?

Valve stem seals are not common...neither is smoking on hard accel.

With your symptoms ...I'd say clean the engine with a good degreaser. Ensure you get it from the top and botton. Then you will know about leaks 100% instead of guessing.

How many miles are you putting on the oil between changes? GM has stated that 1 quard is normal ~3,000 miles. However if your low light is coming on..you are probably lower than 1 quart.

I've put on around 3,000 miles in two months since the oil change. It was probably a little more than a quart low. I can't remember how far up the dipstick it was with five, but it'* now halfway up the full markings.

I'd say clean the motor down and look for leaks.

The wife'* '04 LeSabre had very similar symptoms...slow loss of oil, with oil coating the pan and lower part of the block, but no direct evidence of the source of the leak. And no spots on the garage floor.

Turns out it was a broken oil pan gasket. My suspicion is that the oil only leaked out when the car was running, with the oil sloshing around on top of the windage tray in the pan.

Mine leaks a little out of the front valve cover gasket, but only if the car sits for more than a few days. My car had been out of commission for about a week and a half after a hit-and-run incident I had a little over a month ago, and although it didn't leak enough to spot the concrete, it put a nice coat on the exhaust manifold that freaked me out when it started burning off (I thought the thing was on fire for a second ).

Do like Bill has said and clean the motor as best you can, then look for evidence of leaks.

Tom