1 router 3 pcs all different download speeds

i have 1 router that connects 3 different pcs and if i do speedtest on them mine which is supposedly the best is the slowest why is this

There are a LOT of variables that wouldn't be obvious. If there are several programs running on your PC at the time of the test, it would affect a speed test. If other PCs have consumed a large portion of the pipe, it would affect the test. I would venture a guess that if you turned off (or unplugged and/or turned off wireless) of all other devices for the test you'd see a big difference in the result, too. To be honest, the speed test should only be used to test your connection to the greater Internet and should be done with as near to zero interference running. Disable all programs, all extra things, turn off *all* other devices, etc. then run the test from one PC.

thanks for the reply,i have done the test heaps of times what i cant understand is mine seems to be capped at 2.6 it wont go past it and both other pcs ,[all wireless connected] do go up to 3,i was running mine through Ethernet cable and it was the same,the only thing different is i have changed to an open dns,others are not ,and im not sure how to change it back do you think this is the difference

what test are you using? Try This site if you are in the US. Post results here (trying to limit of course, and do the test serveral times each.)