kdbgoat said:
Changing oil at 3k, even with conventional, went by the wayside decades ago. BTW, the recommended Motor Craft oil is a synthetic blend and is no more expensive than any other oil.
Yeah, ever since I started changing oil in my daily driver silverado based on the onboard computer, I've kicked myself for all the extra work and money over the years changing religiously at 3,000 miles. Just the work of keeping track of it is insane in a way. Supposedly the computer algorithm considers many variables such as temperature and time, not just miles. Granted, the older engines may not have been as well designed, and the oils are probably better now, but still.....
My E-450 motorhome isn't sophisticated enough to have such a computer indication, but I figure it isn't really so different. The thing is though the time component. It sits a lot between miles.....so just like with tires, miles isn't really a great variable to consider.
A long time ago I was working as a Maintenance Engineer in a large pulp and paper mill. My group was responsible for predictive and preventative monitoring and maintenance of pretty much all the rotating equipment in the mill. Lots of motors, pumps, gearboxes, fans, etc.... A lot of what we did was to oversee maintenance based on condition, and not just time or 'miles'. One of the things we did was to work with our lubricant vendor, which at the time was Texaco. Texaco would periodically send in an engineer who would sample oil form some of the larger or more critical equipment, and take it to a lab for analysis. I learned from them the reason for the time element.... remember the old guideline was something like change engine oil every 3 months or 3,000 miles? Well I was told that the oil is a blend of molecules....some long chain and others are short. The short chain molecules would evaporate out over time, leaving the long chain stuff.....'sludge'.
Anyway, my point is this.... when I was faced with this question, I decided to go with the synthetic, figuring that I'd not usually get to the miles limit even over a long time.... not even close, so I would ideally want to use that oil over a longer time to get more out of the $ spent..... so I wanted to be able to consider that I had a better performing oil so I wouldn't feel so guilty about pushing outside of the 'time' specification. I'm not saying this is the best way, or even correct. I really have no idea how the synthetic performs in regard with evaporation or any other time consideration when compared against mineral...It's just the justification I used when considering this question.