kev, if I am reading your OP correctly, you only live off $2200 to 2300 month on your $135K gross income ($26,400 to $27,600 annually). Your rent must be very reasonable. I live alone and have never been able to do that on my ~$45K income. My best month (expense-wise) was $2750 and that was a month where I had no (bimonthly) water/sewer bill and BEFORE Obamacare came into the picture. However, I am a homeowner with all the attendant expenses that go with that dubious honor :=0.
I love the Lexus F-Sports (mainly their looks and the fact that they have an 8-spd transmission with paddle shifters) :=) However, if I ever bought one, it would be the RX. The IS is quite small and I haven’t looked but I’m sure its “trunk” is useless. I’m not sure it needs premium gas (the 2015 RX doesn’t) and I can’t imagine that an oil change for it costs $100. I could see $50 because the price of full synthetic oil has gone up a bit in recent years. The 2014 CPO sounds like a very fair deal if you really want an IS. You mentioned you would keep the Lexus for 15 years. If truth be told, it will very likely last more than 25 years or >300K miles, especially at the 9600 typical miles per year you state you would drive it (800 miles per month) before needing any major work on its engine or transmission. Of course, the years you take road trips with the vehicle, your mileage could easily go over 12K. This is all assuming that you maintain the vehicle properly, including replacing its timing belt and water pump every 90-100K miles (a pricey repair). And if you’re not going to get an AWD model, stay off rutted dirt roads, etc, which will tear up your CV boots, over and over. (Learned this lesson the hard way … my next vehicle will be an AWD/4WD :=0)
Seriously, if you like to ski or go hiking in the mtns, I would get an AWD RX (new or used) if I were you, unless your existing pickup is a 4WD model.
I don’t see any reason why you shouldn’t get a passenger car (or “crossover”), since you don’t have one. Your “girlfriend” can mind her own finances and choose her own vehicles. The Lexus is a great choice. Toyota products (new or used) are the most reliable vehicles in the world, IMO. I’ve owned 9 of them in my lifetime and have no regrets, whatsoever.