I e-mailed Rotella about the oil drain interval, this was their reply. It sounds like what Cary says.
"Both ROTELLA T SAE 15W-40 and ROTELLA T Synthetic SAE 5W-40 are extended drain capable.
Recommending a drain interval for a specific engine is risky, without knowing the oil system capacity, what oil filtration is used, the current condition of the engine, how it has been maintained, what duty cycle it operates in, what fuel economy it gets, how well the engine is operated, and what engine life the owner expects.
A decision to extend oil drain interval should balance expected benefits against risks that might accrue. The engine manufacturer recommends a drain interval that in their experience provides optimum engine performance and durability. To maintain warranty coverage, you should follow their recommendation. Choosing a longer drain interval invariably involves some compromise.
You may want to consider extending drain interval once your engine is beyond warranty, especially if you operate in light duty service. But understand risks you might incur. In the process of protecting your engine from excessive wear and deposits, oil additives are consumed. At some point, no matter what oil you use, oil will reach a condition where its performance is compromised. Finding that point requires used oil analysis. To find the optimum drain interval for your engine and your duty cycle, with the oil you plan to use, I recommend used oil analysis as a tool.
Oil may also be contaminated in the crankcase. Fuel, coolant, and dirt are all contaminants that compromise lubrication. The longer you leave oil in the crankcase, the more risk of exposure to these contaminants. This is another reason used oil analysis helps.
Here’s a way to determine optimum drain. Switch to the oil you plan to use, and operate for two oil changes at the interval you’ve been using. Sample drain oils and have analyzed. If for both samples viscosity stays in grade, TBN remains several numbers above three, contaminants aren’t present, and wear metals are acceptable, then extend drain interval by 25 percent. You may keep increasing drain until one of the indicators shows distress, but the longer you go the more risk you incur. Keep sampling and analyzing drain oils, because normal engine wear and tear will cause increasing stress for your oil.
I hope this discussion helps.
Regards,
Peter"
I was thinking of doing the two short oil change but it was a cold winter and I was lazy
"Both ROTELLA T SAE 15W-40 and ROTELLA T Synthetic SAE 5W-40 are extended drain capable.
Recommending a drain interval for a specific engine is risky, without knowing the oil system capacity, what oil filtration is used, the current condition of the engine, how it has been maintained, what duty cycle it operates in, what fuel economy it gets, how well the engine is operated, and what engine life the owner expects.
A decision to extend oil drain interval should balance expected benefits against risks that might accrue. The engine manufacturer recommends a drain interval that in their experience provides optimum engine performance and durability. To maintain warranty coverage, you should follow their recommendation. Choosing a longer drain interval invariably involves some compromise.
You may want to consider extending drain interval once your engine is beyond warranty, especially if you operate in light duty service. But understand risks you might incur. In the process of protecting your engine from excessive wear and deposits, oil additives are consumed. At some point, no matter what oil you use, oil will reach a condition where its performance is compromised. Finding that point requires used oil analysis. To find the optimum drain interval for your engine and your duty cycle, with the oil you plan to use, I recommend used oil analysis as a tool.
Oil may also be contaminated in the crankcase. Fuel, coolant, and dirt are all contaminants that compromise lubrication. The longer you leave oil in the crankcase, the more risk of exposure to these contaminants. This is another reason used oil analysis helps.
Here’s a way to determine optimum drain. Switch to the oil you plan to use, and operate for two oil changes at the interval you’ve been using. Sample drain oils and have analyzed. If for both samples viscosity stays in grade, TBN remains several numbers above three, contaminants aren’t present, and wear metals are acceptable, then extend drain interval by 25 percent. You may keep increasing drain until one of the indicators shows distress, but the longer you go the more risk you incur. Keep sampling and analyzing drain oils, because normal engine wear and tear will cause increasing stress for your oil.
I hope this discussion helps.
Regards,
Peter"
I was thinking of doing the two short oil change but it was a cold winter and I was lazy
), and so far no issues I can trace to, or even suspect may be from, my oil change procedure.
