No matter how litter u used, it's depends on how Capistance generated by fule sensor . When tank is filled at height h by fuel , there will act two capacitors with capacitance C1 and C2 and they are in parallel. Here C1=LA1k1ϵ0=d(wh)Kϵ0 and C2=dA2k2ϵ0=dw(L−h)ϵ0 (for empty space k2=1) now Ceff=C1+C2 or dwLKeffϵ0=d(wh)Kϵ0+dw(L−h)ϵ0 or Keff=LKh+L−h=L(K−1)h+1 If h=43L,Keff=L(K−1)3L/4+1=4(3K+1)