which oil weight is best for older explorer
 

I was just wondering if i should switch from 10/30 to a heavier oil since my 2000 explorer has got 200,000 miles on it.

no, 10w30 is a good weight oil for your truck. It might have come with 5w30 as factory fill. Some will say that thicker oils will fill worn spots inside the motor, but it can also cause low oil flow when cold and lack of oil is not good.

If it's not using an excessive amount of oil then the 10-30 should be fine. As long as the engine has been taken care of you shouldn't have to go to a thicker oil. Sometimes if your burning a little bit or you can hear the main bearings starting to get noisy then a thicker oil will help.

Being that 10w30 is not spec'd by any maker any more the grade of 10w30 is in the ranks of 10w40 and 20w50. A 5w30 will run circles around it because of the extreme SN and OE requirements! For me a 5w30 SN is all I would use year round in that engine!

My recommendation is to use the same oil as when it was new. There is no reason to use anything other than 5w30 in it. If you did want to use a heavier oil use a 5w40. All a 10w30 or 10w40 is going to do is increase startup wear. The wear and tear of your engine over time does not significantly increase the clearances between parts. In fact, the most important lubrication points, the bearings, will only wear a few hundred thousands of an inch over hundreds of thousands of miles, certainly not enough to justify changing the oil weight. Over 98% of all wear to end the engine occurs at startup. If you increase the oil's cold viscosity, it takes longer for the oil to flow, and even if for a tiny fraction of a second, any slowdown in the flow at startup results in increased wear.

I know all to many people who had a great running engine and decided to use a higher weight oil because it was old (over 100,000 miles). Within a year or two of doing so, their engines are burning oil (they did not burn oil before the switch). I seriously question which is the cause and effect. The theory is that the thicker oil sticks to the parts and does not drain as quickly. I think in reality, when the car stills for several hours between startups, the oil drains of the parts the same regardless of viscosity, its all about how it flows when you turn that key. This slowdown caused accelerated wear and that in turn causes the oil burning problem. My lowest mileage vehicle right now is my '97 Ford Aerostar 4.0L at 168,000 miles. Despite its age and mileage it burns about 1 quart of oil every 10,000 miles, or in other words, it basically doesn't burn oil. My Focus is having similar results, its a little over 170,000 miles. My Taurus however is burning some oil. My Thunderbird has external leaks and I think the turbo is leaking, but it has a right too, its only 24 years old.