Will people think negatively of owning a nice car in grad school? I graduated from college 5 years ago, and I was very fortunate to graduate with no debt. For the 3 years after graduating I worked hard, had solid employment, and saved very carefully. This afforded me the opportunity to use a portion of those savings to buy a used car that people comment on while I am driving down the street which I have owned for 2 years. It looks a lot nicer than the cost because I bought it after a large portion of the value depreciated. I love the car, it is very reliable, and I very much want to keep it. 

I know I am supposed to be a "poor graduate student", and my offer included funding plus a stipend, so I consider myself very fortunate.

I was very adamantly told by someone that owning such a car would make me look bad, and that if funding became tight I would get the short end of the stick because my car was too nice. He said the exact same thing happened to a fellow graduate student when he was in a PhD program at the same school 30 years ago.

If it really would reflect poorly on me to have a certain car I'm willing to take a step down, but I wanted to hear from others. Is this perception accurate?
[This answer is based on my experiences in the U.S., specifically in math grad school but I think many fields would be similar.]

Your fellow graduate students will initially take your car as evidence that you're rich.  They'll probably wonder whether you'll be a snob, but personal interaction should allay those fears.  Once they get to know you, there will still be comments and jokes about your car for the entire time you're in grad school, but I don't think it will be a real problem.  In the program I was in, most grad students didn't have cars, and the ones who did gained a little popularity if they took their fellow students on road trips (or even trips to get groceries or see movies), so your reputation may even benefit from having a fancy car.

Faculty don't necessarily know whether a student even has a car, let alone what sort of car, but this sounds like a car that will lead to rumors going around the department.  You may get similar reactions from faculty as from students, but they are less likely to care about social interaction with you (for example, whether you're a snob).  Your apparent wealth could theoretically play a role behind the scenes in allocation of funding, but I don't think this is likely, and it would be inappropriate for it to be a factor in most decisions.  The most plausible scenario might be if money were tight and you requested extended funding beyond the years you were promised.  If the department head is deciding which requests to approve, there's not enough money to approve everyone, and your car leads to a reputation of being rich, then the car could work against you.  However, I don't think this is likely enough to be worth worrying about, and you can always address any rumors about your wealth with your advisor early on in grad school if you think they might be a problem.

The main disadvantage I see is that your fancy car might be your most salient, defining characteristic, forcing you to work a little harder to establish yourself in people's minds for your research rather than your car.  Once again, I don't think this is a big deal, but it might make you feel a little uncomfortable knowing that half the department thinks of you primarily as a person with a car.  (On the other hand, this is far from the worst thing you could end up being known for.)