Quick (most likely stupid) fuel line question...

Redoing some of the fuel lines on my truck. Correct me if I'm wrong but a single flare on a fuel line is sufficient, no? I always thought you only needed to do a double on brake lines. Thanks for any input...

 

If you are doing AN 37deg with the nut and seperate sleave then its a single flare
If you are using inverted flare fittings then you go double.Inverted flare crushes the flare into the fitting to make the seal whereas the AN sandwiches the flare between the fitting and the sleave

 

Don't waste your time with single, they split and leak, if your going to take the time to do it, I'd do it well.