Originally Posted by ym42
Hi BITOG folks! I have an old high mileage back up car - Mustang 4.6*V8 that I do not drive much these days. How long can I keep the synthetic oil inside the engine before changing it? I do not drive much, but when I do, its all long highway trips... What is the best place for a buck to get a UOA that includes TBN? Thanks!
I have a similar situation with an older Porsche, I drove it around 4500 miles last year without changing the oil, and maybe 3000 or 4000 this year and plan to change it this Fall. It's a large sump at nearly 10 quarts and I use a high TBN oil, Mobil 1 0w-40 FS. Also, I usually drive it longer distances like a road trip here or there, but also some back country road cruising on some shorter runs.
I have confidence two years will be fine. I'm not going two years between changes to save money per se, I really believe two years is totally fine. It sounds like you're in a similar situation with your Mustang. And like you and others have mentioned, a UOA certainly wouldn't hurt for extra confidence.