I bought my wifes 2007 300 SRT 8 on the last day of the month and on the last day of the year 2009. It only had 16000 miles and loaded out and a 1 owner car. I had been watching this car for over a month. Between the economy and the constant snow and bad weather I had an advantage. Went in a test drove 3 different 300's. They were and had been asking 32,000 for this one. Went and drove it with the dealer. Came back in and offered him 20,000 cash. He told me that he couldn't do it, no way, no how. I asked if he would take the offer to the sales manager, he said he would, but told me to expect the same answer from him. He came back with the sales manager, the sales manager said they couldn't let me have it for 20,000, but if I bought today they would let it go for 21,200. I told them to write it up. Last day of the month works really good. I bought my Daughter's BMW, they were asking 6,600 for it. We discussed the price, I told him I thought it was to high, he told me to make him an offer, I told him I would give him 2,500, ended up getting it for 2,800. This was at one of Tulsa's biggest Chevy dealers. Last day of January. My wife about fainted when they gave it to us for 2,800, after elbowing me for offering 2,500. the Beemer had a loan value of over 7,000.
Wait till the last day of this month go in and really lowball them, if not, wait till the end of July. These trucks aren't blowing out of the dealers with the gas and economy the way it is. It never hurts to ask, you just might get what you want.