There are a couple things I would have done differently in the photos you shared. As you take more pictures you will notice some little things that make good photos, great.
For example if you permit me, 
I would have put the railroad tracks in the center of the photograph . Kinda like the diminishing returns of the parallel lines. And the rail in the other photo adds nothing but obstruction. Still your photos are very nice and there will always be "critics"!
Besides your equipment, the Canon T4i and a 24-105mm f4 L, the addition of some post processing software would be a fine idea. Photos are not solely made in the camera!
Hi "grandma"! I am a grandpa and I worked for Hallmark Cards for 40 years. I am still taking pictures so don't worry too much about 'burning out'.
I looked at you flickr page and it looks like you don't need too much help. 
The only thing I would still recommend is watching the background.
Secondly, the Canon 75-300mm f4-5.6 is not in the same class as the 24-105mm f4 L. If you get the "L", look further for a bigger zoom. Unfortunately as the zoom ratio gets bigger the lens gets worse in picture quality, if that is important to you.
You know you can always get "two feet" zooms? Yes, you can get some very nice prime focal length lenses and walk to zoom them!
Some "better" choices would be the Canon 70-300mm f4-5.6 IS USM or even better the 100-400mm f4.5-5.6 L IS USM.
They are going to cost you more but from your flickr page and what you have said, I believe you would get your good use out of lenses of this quality. Because it sounds like you really enjoy photography.
Sigma, a series of lenses I have come to like lately, has some zooms in this same price range that go up to 500mm. Their
50-500mm f4.5-6.3 APO DG OS HSM is a really nice lens and is on sale right now. Keep in mind, however, it is not a Canon "L" but it doesn't cost like 'L' either. (Pun intended!)
Al the best,
EB
These were taken with the Canon EF-S 10-18mm f/4.5-5.6 IS STM Lens
@AliceBell wrote:I am also interested in this. I would like to take such photos!
I have photographed a few car shows, just to give myself a reason to use my cameras. Using a full frame camera, I have photographed cars over a range of 14mm to 100mm. I like the results at 35mm the best.
As noted above, a slightly wide angle lens works well on cars. A Canon APS-C sensor body with a 22mm lens is equivalent to a 35mm on a full frame body. [The standard 18-55mm lens would be almost ideal on an APS-C body, which is roughly equivalent to a 24-70mm lens on a full frame body.]
Getting good exposures on super shiny cars in bright sunlight can be tricky sometimes. You will frequently get blown highlights, because the camera’s metering can easily be fooled. So, I dial in a bit negative exposure compensation when i take the shots, and just accept the fact that there will almost always be small reflections of blown highlights. After all, that is pretty much what you eyes see when you look at the shiny cars, anyway.
