Anyone used an auto insurance comparison tool that actually works?

I am pretty sure I am overpaying but every time I try to shop around I end up on four different websites entering the same information over and over and still cannot tell if I am actually getting a better deal or just a different number… Is there one that actually pulls real quotes side by side without just selling your information to every carrier and flooding your inbox? And did it end up saving you anything meaningful or was it more hassle than it was worth?

thanks everyone