No, I don't think anyone will counterdict me saying that crush washers should go on both sides. Other than that you can find out the tightening torque spec, and make sure they are tight enough. Once on another car the new fuel filter leaked, I really had to tighten the heck out of it but it stopped. The risk of this is stripping the bolt or the threads of the hole. I'm just saying I did this once and it worked, not that you should do it. The crush washers won't be good if it is super tight and still leaks, don't reuse them if it is already really tight and still leaks. I notice that crush washers are made of different material sometimes, if you end up getting new ones mabee a different material will work better.