Oh, Time travel’s one of those tough ones to figure out the right way to do things.
First and foremost, the car that should be brought back needs to be something that could somewhat blend in. For those who’ve seen it, Back to the Future shows an excellent problem with time travel in a car: If your car looks too modern for the year you’ve gone back to, it’s not useful.
Second, the year makes a huge difference in what you need, as fuel availability may pose a bigger problem than you originally thought.
Third, assuming we’re doing this type of time travel as a casual thing, not to change the future, but to observe the past, it’s important not to bring anything back that could theoretically give a jump-start to the technology of the time.
Alternatively, if you’re going back in time to change the future, you’d want to bring back things that could right the wrongs of the future, like bringing back a clean-running diesel to show the Detroit Three in the US how to do diesels in the 70’s and 80’s, or bringing back a high-flow three-way catalytic converter in the dark days of forced emissions equipment.
Fourth, you have to keep in mind that any repairs that you need to do to your choice of car has to be able to be done with period-correct materials. So, the best material your car could be made out of is steel, as most cars for the longest time have had a steel construction.
Effectively, the best car for the job would be a car from the era you planned to go to. Though, to do things properly and recommend a car from this time to go back, assuming Alternate Timeline theory (thereby avoiding potential paradoxes from doing this), you go back in a vehicle that could handle just about anything, and will run on commonly available fuels.
My choice would be a diesel-powered pickup truck. Why? Given my location (the USA), we’ve had diesel for a long time, just not used in cars. It’s used in trains and large trucks, as well as in tractors. It’d be a commonly available fuel, free from lead, requires little change of the components in the truck itself after removing the emissions equipment, and being a truck, you know they’re steel body on a steel frame.