Get out or get in, that’s the question…

Servus people, I’m talking to my brother about fuel consumption. And it’s all about getting out of gear to roll longer. Now my brother thinks that’s crap, because then the (have forgotten the exact word) “empty injection” would start and I would have consumption with it. But if I let the gear in and let it roll, nothing would be injected and therefore no consumption. However, I think that if I would take out the gear without the engine brake more Since I am quite de facto oriented, I would like to see this in numbers! What sizes do you think I would have to include in order to get a benchmark? I was thinking for the time being: – Current speed – possibly gradient – Power of the engine brake – Air resistance of the Audi 80 B4 and later maybe still rolling resistance of the tyres Where could I get the power of the engine brake? Or varies the speed of the vehicle. r Speed? Questions about questions mfg Chris