No harm will come from switching back to mineral (dino) oil. As a matter of fact, I often switch back and forth on my Isuzu Rodeo. Due to a sticking hydraulic lash adjuster that makes the valve tick occasionally, I switch to a Mobile 1 0-30W oil for an oil change, which according to the factory is supposed to relieve the problem. The only thing is this: I don't care what the oil manufactor SAYS their oil can do for change intervals, I go by the manufacturer's recommendation for extreme service, which is 3500 miles. Changing with synthetic every time is expensive....

I have been very happy lately using Rotella 5W-40 synth, or Rotella 15W-40 dino oil, available at Walmart in gallon size.

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On the plains of hesitation bleach the bones of countless millions who at the dawn of victory, sat down to wait, and waiting -- died