For my visionline and legacy steamers with the wistle steam effect I will only use lionel premium. It is thiner and flows better through all the various tubes and funnels to the various smoke units and out the appropriate holes for each feature. Now for just plain single stack smoke units like mth or older lionel tmcc or legacy I will use megasteam for all those. Mostly due to the size and cost factor. I can order bigger ounce bottles of megasteam vrs. The small lionel bottles that are less than full when brand new.
How I know lionel fluid is thinner than megasteam you say. Go to youtube and watch laid off sicks video on 20 drops of smoke fluid. It will give you some good advice about smoke units and fluid comparisons. Then you can decided what will work for you. Every engine and smoke unit is different so one size fits all does not exist or apply here. There is know right answer. Just what works best for you in your particular engines and what amount of smoke output is acceptable to you.
