A week ago I bought gas April 17, and a few days later my 1999 LHS 3.5 liter started running rough like mis-firing. It has happened before if I buy gas from certain stations. I avoid those now but I bought this from a station who I have never had problems before, but quit buying from them because of the brand (comes from a country that starts with a "V". I defiantly will not buy form them again. Well the reason I did this time was they were 10 cents per gallon cheaper than the other stations in the area. They had a lot of business that day. I guessing that I got there when they were getting down to the bottom of the tank. Now here is the kicker....I also filled my old 92 F-150 there just a half hour later. I have no problems with it. It runs just fine. Is the LHS just more sensive to bad gas?? I took it to Auto Zone and had them put their tester on it and it came up with misfire #2, the same thing it has done before when I run into this problem. The guy said that this does not mean that that is the problem. He said no diagnostic equip would say what was wrong with it, but the only way besides draining all the “old” gas was to drive it all out and change the fuel filter.