Let us remind ourselves that foreshadowing is when the author plants hints in earlier chapters about what is to come later on in the novel. You might want to consider the description of Randy's car that we are given at the beginning of the second chapter of this great novel. Note how the one negative element about his car seems to point towards some kind of future problem with it:
Randy got into his new Bonneville. It was a sweet car, a compromise between a sports job and a hard top, long, low, very fast, and a lost of fun, even though its high-compression engine drank premum fuel in quantity.
Given what we know is going to happen at this stage in the novel, we therefore are given grounds to suspect that this might be an issue with the car, as the nuclear holocaust will undoubtedly make securing fuel for Randy's car difficult.