Nico Rosberg setting the pace in the first practice session and Lewis Hamilton topping the second at the Circuit de Spa-Francorchamps.
McLaren's current car is a "rolling laboratory" for the start of the works Honda era beginning in 2015.
Eleven races down, eight more to go in the 2014 Formula One season.
"No team orders" to settle the outcome of the title battle.
Mercedes has vowed to stick with Michael Schumacher as the F1 legend continues his recovery from a skiing fall last December.
Niki Lauda has put his mind to the problem of F1's dwindling television and spectator audiences.
Mercedes' title-warring drivers have been told they must follow team orders over the remaining eight races of 2014.
Mercedes has moved to put the intensifying battle between Lewis Hamilton and Nico Rosberg behind closed doors.
Felipe Massa finished fifth and Valtteri Bottas eighth.
Toto Wolff: "Obviously, we need to sit down, discuss and analyse the moment when Lewis was asked to let Nico pass..."
Eric Boullier: “We tried our best, but it didn’t work out.”
Nico Hulkenberg: "We need to be flexible with the strategy tomorrow as it’s usually difficult to overtake here.”
A fuel leak saw Lewis Hamilton eliminated in the Q1 phase without setting a time.
Friday practice in the scorching Budapest heat.
Kevin Magnussen: “I may have ended FP2 fifth-fastest, but I think our job is going to be a little more difficult than it was last weekend."
Felipe Massa: "We have run both cars with the new rear wing and it's very positive so far."
Lewis Hamilton narrowly edging Nico Rosberg to top both practice sessions at the Hungaroring Circuit.
Championship leader Nico Rosberg insists he is not worried about racing on 'a Hamilton track' this weekend in Hungary.
According to Autospring, Max Verstappen has decided to team up with Mercedes.
Two top teams have admitted they considered lodging a protest against Mercedes at the German Grand Prix.
Niki Lauda slammed the cars produced by Mercedes' grandee rivals in 2014.