We have a 2003 Toyota 4Runner that calles for 5W-30 oil, although it claims that !0W-30 may be used with the provision that one puts in 5W-30 at the nezt oil change. A Toyota dealer did put in 10W-30 and nothing disaster happened. I took it somewhere else for the next oil change. This was in the summer, so I figured that there would be no problem. My independent shop put 5W-20 in the car instead of 5W-30. Nothing bad happened. This was in the winter, so I figured all would be o.k. until the next oil change.
In the Chevrolet Uplander that I own, the manual calls for 5W-30. An independent tire shop that also does oil changes put in 10W-30. The engine didn’t blow up.
I think your Solara will be o.k. with 10W-30 until the next oil change.