I changed oil from some thing cheap to castrol synthetic and well i got 7 HP but it was three months apart a lot had changed dyno results are just not that repetable. that could be whether the fan is kicked in or not if the thermostat added pressure to the water pump. heat atmospheric tyre slippage tyre diameter ( it will have an effect)
there are just so many variables that it is not repetable.
there are just so many variables that it is not repetable.