First, Mobil introduced MX4 to the offroad motorcycle and wheeler segment in North America, so the MX4 moniker actually made sense.
Second, Mobil put the MX4 in Racing 4T bottles and sold it to the rest of the world. MX4 and Racing 4T were exactly the same product.
Third, the V-Twin oil was introduced in North America with the V-Twin moniker a reflection of the most popular engine type in the market. V-twinners tend to like heavier oil viscosities, not that they actually need them. The V-Twin oil rated favorably in independent testing, right up there with the best specialty brands like Royal Purple and Amsoil, far better than any other commonly available brand. V-Twin lacks JASO MA certification because the standard did not exist when the oil was first formulated.
Fourth, MX4 was renamed Racing 4T because the rest of the world calls the stuff Racing 4T. Same stuff.
With the passing of time, MX4/Racing 4t (same stuff) needed to be upgraded to new additive technologies already applied to the newer V-Twin oil to maintain its performance level above the commonly available competitors. The oil changed, the label name didn't. Essentially, the V-Twin additive package was used with a 10W-40 base oil instead of a 20W-50 base oil.
Hence, we now can choose from two of the best motorcycle oils available anywhere at volume prices. Choose which to run based on riding conditions and type of riding to be done, then pour with confidence.