Goo Gone. Then wipe it all down with a cloth soaked in Windex to get the last bits of of the Goo Gone oil. Goo Gone used to be mostly citrus oil, but the last few years it's clearly being augmented with some petroleum distillates; however still my solvent of choice for adhesive on plastic. No evidence that it isn't just as safe on plastic as it's always been, but it is now a bit petroleum stinky. I just tried some on the lens on my 189; yup, safe as ever.
Citrus oil is principally limonene and I know from experience that limonene is a highly effective dissolver of polystyrene, acrylic and ABS so caution is needed. Brief application may dissolve label adhesive before it dissolves the plastic underneath the label but please, please, don't leave difficult labels soaking in the stuff on plastic surfaces or you may well return to a gooey mess. A cautious approach is strongly advised.
Be careful with IPA; it can cause some plastics (like polycarbonate as used on Fluke meters) to go cloudy, especially with age.
Be careful of any solvent on polycarbonate, it's very prone to a phenomenon known as solvent crazing, which is a close relative of of stress corrosion cracking. Be especially careful near any polycarbonate that's used for safety purposes (guards, helmets, anti-projectile barriers) as solvent crazing can make it fail spectacularly in stress without being obviously apparent beforehand.
I've used Goo Gone for decades on every kind of plastic you can imagine. They used to advertise "100% oranges for a natural clean" or somesuch crap. It is DESIGNED for getting sticky stuff off of plastic, and recommended usage is to soak stubborn labels off with it. I spent most of a decade in the recycled electronics trade where I went through a bottle or more a week, and never had a single casualty due to the stuff. The same cannot be said of alcohol or WD40, which will peel up applied vinyl coatings commonly used on steel & aluminum equipment covers.
WD-40 used to be mostly benign a Pat says; but it has become somewhat malodorous in recent years, just like Goo Gone. I suspect the original formula has been similarly supplanted due to the artificially low cost of many petroleum products right now. Again, you have to be prepared to wash it right off to get rid of the stink.
mnem
*Not yet ready for Prime Time*
And this stuff is DESIGNED to solvent weld polystyrene:
I don't wish to get into a battle with you about this, but at the same time I would feel remiss in letting you leave an impression that something orange oil based is harmless to all plastics.
You may have been lucky over the years but anything that is principally orange oil is principally (>90%) limonene and it is well known, and well documented, as an effective solvent for a range of common plastics and is also used as the basis for a number of paint strippers. There are many plastics that are tolerant (polyethylene) to highly tolerant (nylon) of limonene but there are many that aren't, polystyrene, acrylic and ABS being the commonest. Using a limonene based product indiscriminately can and most likely will lead to grief.
I am not saying don't use limonene or limonene based products; I keep it as part of my own collection of problem solver solvents:
I'm just saying that understanding and caution are required in using it.
Clearly, the product is designed for use on plastics, particularly the kinds of plastic used on electronic equipment. Therefore, it is your understanding of the product that is at question here. You ASSUME it is full of limonene, therefore you assume it is hazardous to plastics. You ASSUME that the manufacturer has somehow formulated a product for use on plastic without neutralizing it to be a safe product for use on plastic.
Now which is really more likely here; that your understanding of the product is faulty, or that it is dissolving people's electronics all over the world ever since it was introduced and hasn't been pulled from the market?
I am fully aware of the chemistry you speak of; I am NOT ignorant. I'm telling you that decades of use on all manner of plastic cabinetry, most of which is in a production environment is valid empirical evidence that in this case, you don't know what you're talking about as well as you think you do.
In general, Goo Gone is safer to use for cleaning than IPA, which will remove and smear many types of coatings and paints commonly in use today on electronics; Goo Gone just makes them shiny. I used to use IPA to clean up after Goo Gone; then we started getting gear with micro-rubberized coating that IPA just turns into a flaky mess. Even that is unaffected by Goo Gone unless it's already turned marshmallowy; but by then there's no saving that stuff. The only solution there is to strip it all off, and IPA is good for that, IF it doesn't turn the base plastic hazy.
Yes, of COURSE there will always be the exception to the rule. Yes, you should ALWAYS test on an inconspicuous area FIRST.
But consider this...
due to my extensive EXPERIENCE with the product, I am confident enough in the safety of Goo Gone IN GENERAL that I didn't hesitate to smear it all over the lens of my just-acquired Fluke 189 to make SURE before recommending it to Greg. mnem
mmmm.... solvent....