Switch back to synthetic blend after using synthetic

[baespey]

For the first time in my car's history, I used synthetic oil. Can I switch back to synthetic blend the next time I change my oil? Some people say no and other say that's just a myth, that it's okay to switch back. What about for a 2007 Ford Edge with 85K miles on it?

[WWWPerfA_ZN0W]

You can switch back, no problem, as it is OEM requirement anyway. Why did you put in synthetic and why do you want to switchback, just curious.

[TheWizard]

Oil comes in three types in ascending order of efficiency... dino oil, synthetic blend, and true synthetic. Depending on manufacturer's recommendations, there is no reason you can't switch back and forth between any of the three. Synthetic blends and true synthetics are better at cleaning but any oil of a given viscosity will lubricate the same as any other. Dino oils break down much quicker than the synthetics due to molecular sheer so the change interval is lower. It is not a good idea to use a dino oil if the manufacturer recommends blend or full synthetic because the manufacturer is taking the extra cleaning capability and longer change intervals into consideration and the dash oil monitor is calibrated to match. But you could use dino oil in an emergency (what would constitute an oil change emergency?) without any harm to your engine.

 

The one big exception is older, high-mileage engines that have been running dino oil exclusively. Switching to one of the synthetics can cause leaks at some seals. This is not because the synthetic oil is capable of getting through spaces that dino oil can't (common misconception) but rather because the extra cleaning action removes some dino oil gunk that had been effectively plugging a leaky seal. The synthetic oil is merely revealing the existence of a marginal seal. You don't have to worry about that - 85,000 miles is not considered high mileage with today's engines. In the 60s and 70s, 85K would be almost ready for the scrap yard... odometers didn't have six digits because so few cars ever reached 100,000 miles.

Edited August 1, 2014 by TheWizard

[frebrd18]

Good info, I'm running MotorCraft Syn Blend at 6-7k Hwy interval (w/ filter) and I have 95k on my 07 Edge with no sweat. I know that doesn't answer your question regarding switching back but I think the two previous posts have cleared that up. I'm hoping to get 200,000 on my Edge and the way it's running I don't think it will be a problem.