So my car is now over 100,000 miles and I am wondering if I should switch to a synthetic or other (high mileage?) type motor oil. I honestly have no idea what what weight I've been running - just conventional (usually have oil changed at local places), but I'd love to get 10k miles between changes. I live in NC (USA) where we have four seasons (single digits to 100+ degree temps). Other forums comment that Amsoil 0w-30 is good for 35k miles and Shell Rotella synthetic 5w-40 is may be another option. Anyone have any advice for me? I don't seem to be losing/burning anything now, not sure if it's okay to switch and if so, what to switch to. Thanks for any advice!
Synthetic oil theoretically allows 10,000 mile oil change intervals, and there are people on the forum who regularly use synthetic for exactly that reason. For high-mileage oil, I was just reading this article that explains it: Should You Use High-Mileage Oil in Your Car? ยป AutoGuide.com News
Are you consuming any oil between changes, and I assume you're currently following the US second generation 6 month or 5000 mile oil-and-filter-change interval? If so how much?
If you get 20k miles within a year you can try Mobil 1 Annual Protection. There is also Extended Performance which would last 1 year or 15k miles, whichever occurs first.
I considered the same thing recently, I'm at 182k burning a quart per 5,000 miles, most of which seems to burns towards the second half of the 5000 miles. I ultimately decided just to keep two quarts of the Walmart 5-w30 ($2 per quart) in my trunk with a funnel and keep her topped off after the 2500 mile mark. If I'm going to burn it, might as well burn the cheap stuff. I'm not sure if a synthetic would burn less, but I'm not having any other engine issues so just staying as-is.