Lemme take a swing.
This $45 ozone generator from Amazon has helped quite a bit when unfathomable smells have taken over the garage and I need to start fresh with a clean slate of no-stink. Eg. say, 400,000 mile-old gear old (you know, that special kind of "fart" smell?

) spilled all over the floor....even after a good cleaning up of the source of the smell and disposal, the smell still hangs in the garage. And in 90 degree heat in an enclosed garage, that kind of hanging scent does not smell good. It just aggravates you more when you are trying to change out wheel bearings, lol.
Caution though, you can only use these in an UNENCLOSED space, no plants, no animals, no people. It will kill any smells, bugs, bacteria, mold, plants etc. ANYTHING living. But with the garage door sealed and closed, it is a non-issue to allow it to run overnight for a few hours. Appreciate that it has a timer so I don't need to buy a secondary one.
I give it a few days, because it takes a while for ozone to break down (in the summer, it breaks down faster). After about 3 days or so, it's all gone, and I can walk into the garage and smell nothing but "fresh garage". The way it should smell.
Ozone has its caveats but it is the ONLY thing that actually
destroys odors, it doesn't cover them up. And after multiple used gear oil spills, there's no covering that up anyway. Ozone, imo, used carefully and properly, is the only option!
Other than demolishing the garage and starting over
Works great on cigarette/cigar-smoked cars too (probably the ONLY thing that works on that) but you need a LOT of ozone to get
anywhere with that kind of situation. Seal of the car and run it for a week to get results IME.
If you have a garage that stinks, this is your ticket. But make sure you clear it out of living things, and stay out of it for a few days. Recently I ran it 2 hours the night before we left for a weekend trip. The following monday, clean and fresh. No ozone smell either.