Originally Posted by jzwu
Using fluid color/small for assessment is not very scientific. Do you agree? That's the rudimentary method used decades ago on the fluids belonging to that era.
Has anyone smelled the new ATF? It smells really bad when brand new. Color alone cannot be used to assess how usable the fluid is, either.
Blackstone lab has done many engine oil analyses on Mobil 1 synthetic oils from many different owners. I have never seen one report stating that the oil was bad within 10k miles. Changing synthetic engine oil at 5k miles is a total waste.
And Yes, I do engine oil change, ATF change, differential oil change, coolant change and spark plug change, among other car work, myself indeed.
You do seem to have a problem with reading comprehension. My words in my first post were “Initial guide” with the word initial underlined (that mean special emphasis). Examining the ATF color, blotting a paper towel with fluid (looking for pattern spread to indicate excessive oxidation) and smelling the fluid to see if the fluid smells burnt are universally
(emphasis here again) used by auto shops the world over.
Apparently you haven’t looked at many Blackstone reports either. The additives in oil are for the most part sacrificial. If brand new oil is added to a brand new engine the drop in additives (commonly referred to and measured as the TBN or total base number) is fairly linear as the oil ages. However, if new oil is placed in an older engine (especially one that has not been well maintained), the drop in TBN in the first few hours of operation is dramatic as the additives sacrifice themselves against the existing sludge and debris in the engine.
Plenty of report exist showing additives used up well before 10K miles with synthetic oil. It is a common misnomer that synthetic oil additives last much longer than conventional oil additives. While some (like viscosity index improvers in dino oi) are not needed in synthetic, many of the additives are very similar or exactly the same. While synthetic base stock withstands heat better, most additives in synthetic oil are chewed up at the same rate by acid, water, antifreeze and rust.
Being more expensive, synthetic oils have traditionally been sold as lasting longer than dino oil, and while to an extent that is true, by far the biggest advantage to synthetic base stock oils is their ability to withstand high heat while still maintaining a hydrodynamic film in large bearing surfaces, and their cold pour point characteristics which means engines receive relatively fast lubrication at -20F. These two characteristics alone dramatically reduce engine wear and extend engine life.
When I use Blackstone I am not looking to extend my oil changes, but for signs of excessive metals, fuel or antifreeze, suggesting either excessive journal bearing wear or early stages of gasket failure.
For my BMW, my last Blackstone report was with 5197 miles on Mobil 1 0W-40. TBN was 3.2 (objective is to keep it above 1.0) with no excessive metals and no measureable fuel or antifreeze. The comment from Blackstone was to try extending the oil drain interval to 7000 miles the next time.
For my SC430, the last Blackstone report was with 5333 miles on Mobil 1 0W-40. TBN was 2.8, metals were good and fuel, water and antifreeze were all zero. As expected the kinematic viscosity of the SC430 sample at 100C was slightly higher than the BMW, as my wife doesn’t drive the SC430 nearly as hard as I do the BMW. The comment from Blackstone was that there was still active additives left and to try and extend to 7000 miles.
Changing your oil while the additives are still present is the whole idea!!! Could I extend my oil changes to 7K or even 10K? Maybe. But exactly when does the TBN go under 1.0? I simply don’t have the time to mess with it, and I understand the effects enough (I am a graduate engineer) to know I don’t want to guess and be wrong. The savings in extending my oil changes would be the cost of one cup of Starbuck’s coffee per week! Really? I couldn’t care less.
Glad to hear that at least you do your own fluid changes. Now read some more!