I must admit, I use pattern parts pretty often, but I do sometimes worry about quality - particularly on safety-critical ones or ones that could have expensive consequences.
I tend to keep my cars for a long time, and keep detailed records of what I do to them. From these, I know that (for example) I can spend (say) £20 on a genuine CV joint gaiter and have it last about 80,000 miles, or get a pattern one for a quarter of the price, but I'll be lucky to get 20,000 miles out of it. I bought a cheap eBay pair of top front wishbones for the wife's car once (about £30 per side compared to something like £120 a side for genuine ones) but the bushes were knocking again in barely 15,000 miles, whereas the genuine ones lasted 80,000.
I don't mind buying a "Fram" or Coopers filter, but I recently got a pattern fuel filter for a diesel car. It cost about £14 but came in a plain cardboard box and had no name or markings of any kind - no batch code, date code, part number etc. No blanking caps on the pipes. In the end I decided that the potential damage I could do to the rest of the fuel system wasn't worth the risk, so I cashed out £43 on a genuine one.
All these are just a pain in the backside to change, but when it comes to the new generation of aluminium suspension arms and the like, I do sometimes wonder whether they've been made in some Chinese foundry out of recycled Coke cans and are going to suddenly "wilt" on me one day at high speed!
