I don't use the odometer or a time factor, or even road conditions for my decision. When the oil appears fairly opaque on the dipstick, it has enough contamination that it's time for a change. Filters remove particulates down to a certain defined size. Anything smaller passes through. Sub-micron particles can still cause wear, albeit at a slower pace. As a general rule, I can go 5,000+ miles between changes. Working with crude oil, I have access to a centrifuge that we use to check the crude for excess contaminants to decide if the crude is good enough to buy. I have checked my drained engine oil more than once in a centrifuge. The darker the oil, the more contaminants will spin out of the waste oil that has passed through your oil filter thousands of times. Each person has to decide the "economic threshold" for protection vs. maintenance cost for their vehicle. There isn't a right answer. It's an argument that will never end and it's truly up to the individual. Are you going to trade it off every few years, or will you still own it 200,000 miles down the road?
As far as what Ford recommends? I believe that the original 5W-20 recommendation was simply a lame attempt at gaining mpg because of mandates. Thin oil has less drag than thicker oil. When they found that it was causing longevity problems, they back-stepped and changed the recommendation. They did the same with differential oil in many vehicles. It was originally 80W-90 and they later changed to to 85W-140.
Also, remember that Ford it in business to sell new vehicles and replacement parts. Their engineers recommendations and designs are calculated with an "acceptable lifetime" factor.
In the end, how long do you want it to last and how much are you willing to spend to make it last that long, and is the cost vs. benefit factor worth it to you?
As far as what Ford recommends? I believe that the original 5W-20 recommendation was simply a lame attempt at gaining mpg because of mandates. Thin oil has less drag than thicker oil. When they found that it was causing longevity problems, they back-stepped and changed the recommendation. They did the same with differential oil in many vehicles. It was originally 80W-90 and they later changed to to 85W-140.
Also, remember that Ford it in business to sell new vehicles and replacement parts. Their engineers recommendations and designs are calculated with an "acceptable lifetime" factor.
In the end, how long do you want it to last and how much are you willing to spend to make it last that long, and is the cost vs. benefit factor worth it to you?
