The check engine light. Good grief. [/SPOILER]
GORL-CHU is in bad shape since they don't do the normal maintenance required and put the minimum effort into everything.
You don't do an "oil change", you do an inspection that includes filters at least.
Even oil change always includes the oil-filter, it appears that this doesn't hold true for Wommart, changing the oil whilst keeping the old clogged filter (which has all the impurities and dirt in it) is about as effective as doing no change at all.
Even though it's 2019, I don't know why you guys honestly expect two morbidly obese lesbians to know about cars and auto maintainence.
The clerk or mechanic would usually be able to tell them what they need, but that was probably some 20yo stoner who nothing about cars since they went to Wommart, known for their master mechanics
Also that car has to die soon. She's 600. Becky has to be 300 now right? That's 900lbs. What's the limit on her car 1200-1400? Something like that? That poor car.
The Elantra has a curb weight of 2844 lbs. with a gross weight of 3924 lbs, that leaves 1080 elbees for payload such as GOOORLS and hauls, as you've already said Becky plus Amber are already 900 elbees, with Dustin and the Child and the linebacker and some haulage they're comfortably 630 lbs. over the limit.
Running a vehicle at its gross weight limit is taxing and shouldn't be a normal thing, let alone 630 lbs. over, no wonder it's complaining.
Amber 600 + Becky 300 + Dustin 250 + Dana 400 + child 60 = 1610 elbees of GORL power in one car excluding rotissery chicken and 20 lbs worth of journals