  We give results for the Upsilon spectrum from lattice QCD using an improved
version of the NRQCD action for b quarks which includes radiative corrections
to kinetic terms at O(v^4) in the velocity expansion. We also include for the
first time the effect of up, down, strange and charm quarks in the sea using
'second generation' gluon field configurations from the MILC collaboration.
Using the {\Upsilon} 2S - 1S splitting to determine the lattice spacing, we are
able to obtain the 1P - 1S splitting to 1.4% and the 3S - 1S splitting to 2.4%.
Our improved result for M (Upsilon) - M (eta_b) is 70(9) MeV and we predict
M(Upsilon) - M(eta_b') = 35(3) MeV. We also calculate pi, K and eta_s
correlators using the Highly Improved Staggered Quark action and perform a
chiral and continuum extrapolation to give values for M(eta_s) (0.6893(12) GeV)
and f_{eta_s} (0.1819(5) GeV) that allow us to tune the strange quark mass as
well as providing an independent and consistent determination of the lattice
spacing. Combining the NRQCD and HISQ analyses gives mb/ms = 54.7(2.5) and a
value for the heavy quark potential parameter of r_1 = 0.3209(26) fm.
