It is not so much the gear selected but the engine revolutions. Clearly if 5th gear at 30mph is more economical it is because of lower revolutions. Having said that 5th gear at 20mph is not saving petrol, it used to be 56mph being the optimum speed for fuel economy, now we have rev counters. Even Traffic had restrictions and I would suggest when just patrolling instant acceleration was not always the order of the day. Surprisingly fuel consumption WAS watched very carefully when I was wearing my posh blue suit. In fact on more than one occasion we had to park our cars and walk. NOT TOO far was the order in case we need you. Incidentally when I was selling our Renault, I took the buyer for a run and he queried why I missed out gears, was there something wrong with the gearbox. I told him why, on the flat it was often acceptable to change from say 2nd to4th because 3rd was unnecessary. Here in the West Country The coppers in the Cafe to meet the public being the latest idea. Backfired it seems as nobody wanted to. I was constantly told as a Rural officer, I was an unnecessary expense and so all the graduate 'managers' and their number crunching got rid of the Bobby on the beat. NOW they are all whining as the street is where the intelligence is. Each station had a collator who was often an injured copper. He took all our intelligence and sifted it. All gone, I believe it's all pumped into a computer to sort it which will never work. Sorry well off subject again.