I've always have done UOA's on my cars since the early '80's. Here's the trending summary for my '07 Boxster S. Although I agree with JFP regarding the TBN test, I only had it done once since I change my oil at approx 7500 mile intervals (to minimize the fuel dilution -- keeps it under 2%). Most people believe that the TBN is only needed for monitoring long drain intervals (time to change the oil when TBN is either less than 2% or 1% depending on which ASTM method the lab uses), but I think that JFP was eluding to the fact that weird things can happen inside the crankcase (excessive acidity) that would delete the additive(s) faster than expected (I've seen this happen before in a friend's car).
The bottom line is to have the UOAs done and trend the data to keep an eye on what's going on in your engine.
Also, some labs to use are Blackstone, Staveley, Polaris, Bently and many others.
Regards,
paul...
PS: If anyone wants my Excel spreadsheet to use, send me a PM with your email as I can't post it here.
Linear Mode
