My first Infiniti was a 2007 M45 Sport Base with 180k that I bought for $6200. This car had no records and was being driven by a teenager. I drove it until 239k when it was rear-ended and totaled. I had to replace the spark plugs, valve cover gaskets, tie rod ends, the headliner, the AC clutch and the power steering hoses. That’s all I did for the couple of years I drove it until the AC compressor completely went out. Then I had to replace the compressor, condenser, and dryer. The headliner was BY FAR, the worst of those repairs. It had the usual cracked dash but never had the Takata recall. It did not consume more than 1/2 quart of oil in 5k miles. Ran great until the day it was pummeled into submission.
I replaced it in January of 2018 wit a 2006 M45 Sport/Tech Package with 98k, for $9000. This car had only one owner who had all service done at Infiniti of Austin and had all records. This one is in much better shape but I still had to replace the spark plugs, the valve cover gaskets, the battery, the power steering hoses, all the radiator hoses, the belts, and all the tensioner/idler bearings. The headliner is just now starting to fall right at the windshield. I had the Takata recall done on this car so I got a new dash to replace the old cracked one. She doesn’t consume any oil that I’ve noticed.
Things to look for:
1). Pull down the Splash Shield under the motor and look for pooled fluids.
2). Check all power steering hoses but pay special attention to the high pressure hose. It is expensive and can only be purchased from Infiniti.
3). Check under the exhaust manifolds for oil stains. If the valve cover gaskets haven’t been replaced you’ll have to do it anyways. Just make sure you don’t have really bad leaks.
4). Start car when cold with hood up and really listen for ticking (not injector tucking.). You don’t want any, not even faint clicking, coming from under the valve covers. Also listen for timing chain noise.
5). Turn AC on and off. Make sure clutch isn’t noisy
6). Make sure engine comes up to temp quickly, doesn’t fluctuate temp, and that there is no odor of coolant. Check overfill bottle and make sure fluid level is good and fluid is good color.
7). Sit in drivers seat and push back really hard to see if sear moves or creaks.
8) check sunroof operation. Both of my cars had some issues with it not opening in one single movement. Never looked into it.
That’s all I can think of at the moment. They’re good cars. A lot of people talk about oil consumption but I haven’t seen it myself.