Put Non-Energy Conserving Oil In...Any Issues?

I switched to full synth at 120K miles and I saw the Mobile 1 5W-30 for high mileage. Not wanting oil leak issues I was going to try this for 1 cycle before switching to the regular one...

Is there any problems or will it cause any issues? The only thing I can think of is that I may lose a bit of fuel efficiency but it shouldn't cause any wear or anything right?

 

Won't hurt anything.

But even with the 120k, that's not a lot for a Toyota that has been properly cared for. You don't need the high mileage, and go by the weight indicated on the oil cap and the weight/temperature range in the manual.
Use the recommended 5w30, 5w20, or 0w20 as indicated.

 

I've lost about 2 mpg because of it.