I usually like to run my steam locomotives without smoke. However today I ran an engine I don't think I'd ever run with the smoke unit on. It is a Rio Grande Berkshire Jr. cab #8624 (6-38624). I put a few drops of smoke fluid that came with it (#6-02920), and flicked the smoke switch to "On". Once I gave the engine some power, I immediately smelled the smoke. However I could barely detect any coming out from the smoke stack visually. I read the instructions and they stated, "Smoke production is greater at high voltages and when the locomotive is pulling a heavy load or a long consist." So, I slowed it down until it was in front of me, and I lifted the front end until the wheels started spinning fast. I gave it more power and then I was finally able to see the smoke puffs coming out. That made me think the smoke unit must be okay.
My question is whether Lionel has changed the formulation of the smoke fluid over the years or not. When I've used other locomotives in the past with a bottle of Smoke Fluid #909 & #6-2909, I'd see smoke immediately at average speeds. I didn't have to run them at their top speeds to get a decent bit of smoke out of them. I was going to try using the older smoke fluid in the #8624, but I didn't know if the smoke unit was different from the units in the older engines. I didn't want to accidentally screw up the smoke unit in #8624 using the older fluid. If, however the smoke fluid formulation hasn't changed, then what can I do to increase the smoke production in #8624. I want to smell AND SEE smoke when I run it, but it'll run off the rails if I increase the speed all the way to maximum power. Right now I have it pulling its die-cast tender, 4 cars (including coal dump car and gondola with covers), and its lighted caboose around the tree. I don't want to increase the amount of cars by much more, because then it'll be chasing its own tail.