OK, time to humble yourself. Name your biggest automotive mistake. Whether it was a part you bought or work you did, lets hear 'em.

Scott, you can use the story about taking your car in for an oil change if you'd like

Here's mine:

On my last mustang, I was installing a new 8.8 rear end with disk brakes and 3.73 gear. I got all the control arms mounted up, jacked the rear into place, and the shocks wouldn't line up. I tried everything, eventually bending the shit out of the shocks. So I bought 2 new shocks and went back at it. It just didn't look right. It took me about a week or so before I finally realized my screw up. I was trying to mount the shocks to the quad shock brackets . It was bending the crap out of the shocks splaying them way out since the quads mount a few inches outside of the regular shocks. Once I figured this out, it was easy putting it back together. I really felt stupid since that was a pretty boneheaded move,

Another one with the new Turbo 2.3 motor. When the headgasket went, I had some loud valve clatter. My bright idea was to pull the valve cover and start the motor to identify the noise. Much to my chagrin, the 2.3 uses a pressure fed cam with a tiny hole in each cam lobe for lubricating the rocker. You can imagine how neat it was seeing oil spraying in a lovely fountain as it streamed all over the engine compartment and front fenders


OK, now its your turn

 

Letting Penzoil change my oil because I was to lazy to go dump my used oil before hand.

Honestly I have not made any huge mistakes on the Mustang since I always try to plan things out. Sure I have had parts I later changed out but I have been fery lucky to sell them for about what I paid.

Good thread.