From a non engine related area, but it has me shagged. At the power station, we do everything that we possibly can to avoid the exhaust gasses getting to or below "acid dewpoint", at which acids start to condense on steelwork, and eat things up. Keeping the gas temperature high (110C) costs us big time efficiency wise, but allows the ash to flow, and keeps the steelwork where we left it. I've seen the results of an issue where due to air leakage into the gas stream, some rainwater was sucked into the gasses. Created tiny droplets of sulfuric acid. These then started to boil off. Making more and more concentrated acid, which then dropped out in places, and chewed heck out of stuff. So, if during short trip running, acids are being generated, do they really evaporate as temperature gets up ? Or is it simply that high temperature operation simply stops them from forming in the first place ? Higher TBN for around town/short trips/cold weather ?