Reducing the Fuel price will simply put the Pz4 on the field faster than any counter part. It is why the sherman has been buffed in first hand. Both unit are hitting the field around the same time today.
Actually a rushed Panzer IV (no light vehicles) will hit the field a bit later than any other faction's stock medium tank. Ostheer and OKW have to spend the most fuel to get their first Medium Tank (315 / 382 (equivalent cost) respectively). Soviets followed by Ostheer spent the most necessary Manpower to get their first Medium Tank (1310 / 1260 respectively). Soviet medics and medic bunker are included in the Manpower costs.