Changing oil brand/type & UOAs

[Al]

Its certainly possible if the engine is dirty and you put Redline in with Esters that do more cleaning. Obviously if you don't dompletely drain you would see it. Its a valid question but I don't think its a real big deal. I think you will at least see a trend-up or down. But should be able to sort it out somewhat. Certainly Terry could. It makes sense though for the sake of confirmation and better trends to get several samples of the same oil at different seasons/driving conditions. Again-very valid question.

 

[Cutehumor]

seems like the rule of thumb around here is at least 2 runs of the same oil brand before doing UOA; my first UOA, I ran the same oil brand for 2.5 years so I consider my results pretty accurate

 

[Eiron]

How valid are UOAs if the same oil's not run for more than one interval? Are we really seeing what's going on, or are we getting false info from the previous oil's run? For example, what if one oil creates more wear, but also creates a hint of sludge/varnish? Will that sludge/varnish trap the telltale wear indicators? If the next new oil brand/type protects better but dissolves the previous oil's crud, will it appear to be worse than what came before? (This doesn't even consider oil "trapped" in coolers & hoses.) How many intervals of the same oil should we be running before the data is considered accurate? Is one interval enough? Two? More?