My distance traveled script is inaccurate, why?

part = script.Parent

lastPos = part.Position

store = 0

while true do
	local distance = part.Position - lastPos
	lastPos = part.Position
	store = store + distance.Magnitude
	wait()
end

This script does not reflect at all how far the part has moved, based off on another script how fast it is going (the script is on a car)

Not sure why, but any help would be appreciated! (I am aware it is in studs)

Use Magnitude with the subtraction (assuming store is the total distance in studs)

local total = 0
local lastPos = part.Position

while true do
	local distance = (part.Position - lastPos).Magnitude
	total = total + distance
	lastPos = part.Position
	wait()
end