[gmcvt]

DRIVEN OIL was kind enough to respond:

Hello and thanks for your email!



I agree with Blackstone, the reported TBN is at the low range. Based on the amount of calcium present in the used oil analysis you were at the point of needing to change the oil, which appears to be 5,000 miles.



I noticed in your email you mention that you have been running E-85 but the Blackstone report has Unleaded Gasoline. I would suspect the acidic condition that has depleted the TBN of the oil may be based on the use of e85. The oil did not go acidic per say, however it was exposed to high levels of more acidic by-products probably from running E85. That’s one of the things we may encounter with biofuels in general. In actuality the TBN did it’s job – but the 5,000 mile interval was the true maximum point of effectiveness. I was surprised as well but we need another sample to establish any sort of trend. The viscosity is good and the fuel dilution looks OK as well – so I would really like to see the next sample.



Based on the wear metals I would suggest a shorter interval for your next oil change. This will get some of the particulates out of the engine and you will be past the wear in phase. We can then look at the TBN retention sooner in your drain interval (without the wear contamination).



Thanks! Please send me a copy of the next sample so we can continue.