Hi All, I just recently got a 2003 Yukon XL. It's the most expensive vehicle I've ever owned, and we want this vehicle to last a long time. I'd much rather spend a little more on maintenance now, in return for having it running longer. One of the things that I'm planning on doing is switching to synthetics. The truck has 56,000 miles on it, we just got it this year, and while I can't say for sure, I'm going to assume it's always had petroleum based oils in it. I'm going to be switching to Amsoil unless I discover some new information that would suggest they are a bad way to go. I do have a few questions about switching, though. First off, I see that Amsoil sells an engine flush that is for use when switching to synthetics. For a vehicle like mine, with less than 60k miles, is engine flush something I should do, or should I just swap out to synthetic and not worry about flushing? I also have a question about using the engine flush. The instructions say: 1) FLUSH: Change the oil filter and add the flush (about 10% of the oil capacity). Do not overfill the crankcase. Idle the engine 15 to 20 minutes, then immediately drain the old oil and flush. 2) INSTALL: Remove the old oil filter and replace it with an AMSOIL Ea Oil Filter. Ea Oil Filters feature advanced full synthetic nanofiber technology, making them the highest efficiency filters that are available for the auto/light truck market. Ok, so it looks like I need a throwaway filter? Because the first thing you do is change the filter, then you change the filter again in step 2. I guess I should just go to Autozone and get the cheapest filter I can find? Second, I see that they offer a "bypass filter" setup. This gives you some additional filtration past what you get from your standard oil filter. I'm wondering if this is necessary for a truck that's not regularly used in "extreme" conditions (e.g., offroading, towing extremely heavy loads, etc.). While we may occasionally drive offroad, or we may occasionally pull a heavy load, it will not be the norm. But on the other hand, if it is really going to extend the life of my vehicle, it's worth it. I don't want to throw money away on something that's not giving me any real benefit, but I *do* want to do everything I can to take care of this vehicle, so we can have it for a long time.