S
stupar
Guest
Of the cars i have driven of recent (mix of 5 and 6 speed boxes) just under 30 is achievable in 4th without labouring the engine.On a multi lane road it doesn't matter so much unless of course you are travelling slower than lorries meaning they are going to be overtaking and then backing up the traffic and causing congestion. If you'r going to be driving at 25-28 in a 30 chances are you will be using more fuel and more pollution than at 30 when you could be in a higher gear. Your car may just manage 28 in the higher gear but chances are the engine will be on the border of labouring so you wouldn't doing the engine any favours.
Its rare for me to use 5th/6th at 28-30mph unless its a dead flat road with little in the way of obstacles that force you to change your momentum/direction.
Thats my driving style but others will do things differently.