Board Thread:Questions and Answers/@comment-33062853-20171016141954/@comment-33062853-20180224121751

I don't think Quicksiver's top speed has ever been mentioned, but I assumed he was faster just because I have seen articles and videos on it and also by interacting with other people from the community I thought that it has been accepted. But I do think Flash would be faster just because we have seen him greater feats of speed, and with Quicksilver, we just don't know.

Also, not having something that even resembles the SpeedForce would mean that when Quicksilver runs, he wouldn't be able to take the pressure and would die painfully and cause a lot of destruction while doing it. The faster he would go, the more he would burn down and completely destroy everything behind him. So Flash does have an advantage there. The SpeedForce also allows him to throw lightning (at least in the TV show it does), turn into pure energy, and he can also enter the SpeedForce itself and exit it from wherever he wants, so basically teleporting. I don't think Quicksilver would be able to do that since his super speed comes from his mutant DNA, which means he is just fast, like an athlete would be, where as The Flash gains power from another dimension (I am not exactly sure what the SpeedForce is, but I think it is another dimension of sorts).

So even though Quicksilver can't do stuff Flash can, we still (at least I don't) know wether he can time-travel.