Not only an oil use post, but an introduction as well...I stumbled across this site doing an online search for UOA places as my 2003 Suburban has a mysterious coolant leak and I needed a UOA to eliminate or pinpoint the infamous intake gasket problem. Anyway, my wife drives a 2005 Nissan Quest with the wonderful 3.5 VQ35DE powerplant. I steered her towards the Quest (she didn't care what we bought, she took the Dodge Grand Caravan past 100K, now it's my daily beater) because of the engine. I had an '02 Maxima that I put 120K on in 3.5 years (120 mile daily commute). It never so much as thought about blinking. I did 3-5K OCI, with dino, Pennzoil, Havoline and Castrol. With the 120 mile a day commutes, most at interstate speeds of 70 MPH+ it was a dream. I replaced the O2 sensors at 95K and that was it. Unfortunatley I had to let it go because when we added the fourth child it became impossible for the family to fit in it and still obey the law. Now my wife's usage is a little different. I'm afraid we permenantly damaged the engine. We purchased it in April 2005 when we had a three month old. During the next several months it saw a lot, and I mean A LOT of idle time as my wife needed to retreat to the van to feed the baby in a more private setting, especially during all of the other 3 kids activities. I'm talking idling 30 minutes at a time 3 days a week. This was during the first 10K on the car. After the first 10K my wife no longer needed the "privacy" to feed the baby. There is still some idling even today, as rainy soccer practices are not something she likes to stand out in. The idling is no where near the level it was during the first few months. The fan also has the occasional 500-800 mile weekend trip for soccer/hockey tournaments. Every morning the van makes a 3 mile roundtrip to school (during the school year). It probably doesn't get to full temp during then, but other than that all other runs are long enough where it gets to full temp. Unfortunately I was NOT a BITOG follower until recently and kept doing the usual 3-5K OCI with Pennzoil dino (except for one Castrol in there along the way) for the first 18K. At 18K I switched to M1 5W-30. Checking the oil regularly I have had to added 1.5 quarts over the past 4,000 miles. I have four theories as to why: 1) The engine was damaged during all the idling in the first few months because I did not change the oil frequently enough. 2) The M1 5W-30 is too thin for the engine as from my searches here I learned that the Nissan V6 likes thicker oil 3) The manual recommends dino, doesn't rule out synthetics altogether, but seems to recommend dino, and I went against that with the M1 4) My Maxima was driven hard like it was meant to be - acceleration was fun and easy. It had a four-speed AT. The van weighs more (especially with all six of us), has a five-speed AT, my wife drives much less "sporty" and even I do in it because it is a van! Maybe it's not fair to compare the two engines because they don't see the same conditions. I just need to accept it. Where I stand today is the van is at 22,500 miles and I have a 5 quart jug of Havoline 5W-30 and 5 quarts of GC 0W-30. This weekend (maybe sooner depending on work) I need to decide. I am not comfortable leaving in the M1 any longer. Would Auto Rx be overkill on a 22K engine??? Should I open it up and check for sludge??? I can't do a UOA because I think the results would be tainted as I just added 1.5 quarts and it has seen 10 miles since then. It only holds 4.25 quarts which means over one-third of the used oil would be practically new. I've been having my wife drive the Suburban for the past few days until I decide which oil to use. Do I go with the dino, or with the GC 0W-30 be thicker than the M1 (like my searches indicate) and put an end to the oil consumption. Frankly, I'm leaning towards the GC because it is so highly touted here, but 1.5 quarts every 4K gets expensive with synthetics. 1.5 qyarts with Havoline is not as hard to swallow, knowing I can walk in to Wally World and pick up a 5 quart jug for under $9.00, vs. $5.49 a quart for GC. Thanks in advance for the input.