Not to side-track too much, but that’s kind of a neat device! I always carry a multimeter in the car (plus some small pliers, set of spare fuses, analog-dial tire gauge, plus jump starter, and cordless tire inflator, and probably some other stuff I’m not thinking of…flashlight and hi-viz vest…I dunno…stuff).
Cool device, though.
The last time I went to JiffyLube (might have been the first? dunno…definitely the last!) probably ten years ago the dude actually showed me an engine compartment air filter which was very much so not from my car. As in they brought in a filter not from my car to show me. That is some brass balls, but not much else, on the part of that jackass.
I don’t feel like changing the oil filter myself on my newer car, so I go to Valvoline for one of their express sit-in-your-car and wait for a full synthetic change. I find them reasonable, and you can keep an eye on them. They might chide you if you wait longer than 3K miles for another full synthetic oil change, but they can blow me! Really, dudes, you just signalled that your “premium synthetic” oil is garbage and needs to be changed that regularly?
Well, that’s just business, and whatever…easily ignored, and they tend to be pretty nice and have a good coupon discount every day of the week and twice on Sundays.
One thing that bothers me is various places, including tire shops, reading the tire pressure on hot/driven tires. I had a screw in a tire causing a slow leak, so I went to the place I bought my tires (“lifetime guarantee”), and the tech/mechanic wasn’t quite grokking when I wrote out a diagram of what the cold readings of each tire was that morning, and therefore the amount the tires should be inflated at to compensate for the fair bit of driving I’d done that day.
It seems like something tire people, of all people, should know, or even Valvoline quik-fluid-change people. Of course they can tell if something’s super low, but so can I. A mystery.
For all I know there is a standard chart for properly inflating tires to their “cold” correct PSI pressure, but I just take cold readings and inflate accordingly myself, before waiting for the ECU (or whatever it’s called) to signal low pressure. All about the gas mileage and good performance OTR.