It depends on what walmart you're lookinat cuz theyre all different...bigger ones may have it, but here where I live (and I work) we do not...
Example, the Waverly Walmart does not have Lucas Oil additive in single quarts, just one gallon jugs...25 minutes away at the Cedar Falls Walmart, they have a bunch of choices for Lucas products...we just have the one in Waverly.
Your local walmart MAY have it, and it may not. Prices of products and products they stock all depend on the store...every walmart is different for products and even has different prices for the same exact product many times...it depends on the local market...
All services in the Tire and Lube Express do have a nationwide standard I believe, and should be the same price...
....as far as the walmart gumout service goes....
The Gumout treatment they do at walmart is very similar. It's 19.88 Plus tax, and we add a fuel treatment to the gas tank, and use an intake vaccum line (usually the brake booster or PCV valve) and add an engine cleaner...you start the car and let the engine suck up all the engine cleaner, and then turn it off when its all sucked up...then when you start it again (after re attaching the vaccum line) you sit back and watch all the crap fly out of the exhaust

sometimes a lot comes out, sometimes very little....depends on the driving style of the owner, year/mileage of the car ect...lots of times it does trip the Engine light, but usually goes off within a few miles...
(did you guys forget you've got a veteran Walmart Tire & Lube Express Technician here?

)