Hey everyone! I'm a gal who's (slowly) learning to do my own vehicle maintenance. On Sunday I changed my own oil for the first time and I'm proud as punch of myself. Even if it did take me all day. I came here looking for the "best" oil to use, and now that I've read the sticky explaining that, I'm seeking recommendations. 
I have a 2004 Toyota Sienna XLE AWD with 170K miles on it. Owner's manual says to use "API grade SL 'Energy-conserving' or ILSAC multigrade engine oil." SAE 5W-30 is recommended. It says SAE 10W-30 may be used if the former isn't available, but it should be switched back to 5W-30 at the next oil change. Regarding oil change intervals, the engine maintenance light begins flashing 5K miles since last change and remains steady after 7500 miles. They say "If the light is flashing, we recommend that you replace the engine oil at an early opportunity depending on the driving and road conditions. If the light comes on, replace it as soon as possible."
I'm in Seattle and the surrounding areas, and tend to drive 3+ hours a day, much of it freeway, at least 3 times/week. Sometimes that's in horrendously slow traffic. (Worst ever took ~90 minutes to go a single block, but I digress). I drive gently most of the time but dodging near-misses happens often around here. I prefer to drive ~5mph over the posted speed limit, which is apparently considered slow. 
Issues: There is potentially still sludge build-up from when I first got the van nearly two years ago. I initially neglected to change the oil at all, until I realized my mistake. Based on various recommendations, I (think I) cleared most of it out by having several oil changes with a high-mileage oil, Valvoline Max Life high mileage. People told me the detergents in the oil would help remove the sludge. I still see a lot under the cap, so I dunno.
There is also a small oil leak that I won't have the budget to fix anytime soon.
I'd prefer to go as long as possible between changes. I'd also prefer the cheapest "great" oil for my van (does that exist?) rather than just getting the cheapest available and shorting my engine and mileage. And I'm curious as to how expensive the "best" for my vehicle and situation would be, so I can at least consider it. I live in my van, which I have painstakingly converted, so while I'm on a pretty tight budget I also have all my eggs in one basket so to speak and need this thing to last me a while so I can get back on my feet. I'm okay with using either synthetic or conventional oil, whichever will get me there!
Thanks for any help.
I have a 2004 Toyota Sienna XLE AWD with 170K miles on it. Owner's manual says to use "API grade SL 'Energy-conserving' or ILSAC multigrade engine oil." SAE 5W-30 is recommended. It says SAE 10W-30 may be used if the former isn't available, but it should be switched back to 5W-30 at the next oil change. Regarding oil change intervals, the engine maintenance light begins flashing 5K miles since last change and remains steady after 7500 miles. They say "If the light is flashing, we recommend that you replace the engine oil at an early opportunity depending on the driving and road conditions. If the light comes on, replace it as soon as possible."
I'm in Seattle and the surrounding areas, and tend to drive 3+ hours a day, much of it freeway, at least 3 times/week. Sometimes that's in horrendously slow traffic. (Worst ever took ~90 minutes to go a single block, but I digress). I drive gently most of the time but dodging near-misses happens often around here. I prefer to drive ~5mph over the posted speed limit, which is apparently considered slow.
Issues: There is potentially still sludge build-up from when I first got the van nearly two years ago. I initially neglected to change the oil at all, until I realized my mistake. Based on various recommendations, I (think I) cleared most of it out by having several oil changes with a high-mileage oil, Valvoline Max Life high mileage. People told me the detergents in the oil would help remove the sludge. I still see a lot under the cap, so I dunno.
There is also a small oil leak that I won't have the budget to fix anytime soon.
I'd prefer to go as long as possible between changes. I'd also prefer the cheapest "great" oil for my van (does that exist?) rather than just getting the cheapest available and shorting my engine and mileage. And I'm curious as to how expensive the "best" for my vehicle and situation would be, so I can at least consider it. I live in my van, which I have painstakingly converted, so while I'm on a pretty tight budget I also have all my eggs in one basket so to speak and need this thing to last me a while so I can get back on my feet. I'm okay with using either synthetic or conventional oil, whichever will get me there!
Thanks for any help. 
Cool van you got there 