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Gentlemen, I present for you a mystery. The short version is; The tank of Shell 98 that I used last week, pretty much right from the beginning of the tank, until I filled it back up on Wednesday, ran really high EGT and in a really odd way. About 450km of this behaviour. I have EGT probe installed through a hole in the top of the turbine housing. Has been there for years. I'm very familiar with what sort of EGTs the car makes. It will settle to <400°C at idle. It will run at ~500-600°C just driving around. It will run >800°C when stomping it hard or driving it fastish up a steep hill. All normal. When it has had a problem in the past (like a bad batch of fuel I had once that caused it to detonate), the temperatures would go spastically high under load, as you'd expect when it's detonating. Last week, it would run up to 900-1000°C at odd times. Sitting at the lights it would continually climb until it got up there. Driving around it would do it. Stomp on it a bit and it would sometimes stay high, sometimes it would settle back to the ~600-700°C territory you might expect. It would also sometimes run normal EGT and sometimes idle down to the <400°C I like to shut it down at. Other times after pulling up to park it, the EGT would just continue to rise through 800°C. I must stress that I did not hear it ping at all. It also felt very normal. It drove the same, it idled at 600rpm, it was just as fast. It wasn't as if it was running a blocked injector and missing some of its fuel, etc etc. As soon as I put 50+ litres of fresh fuel in it, the car went 100% back to normal. So, theories on what would cause it to happen on a single tank of fuel? What could possibly be wrong with the fuel that would make the car seem normal in all other respects but run such high and odd EGTs? Back story on the fuel. I pretty much only use Shell 98, in Adelaide. Occasionally it gets BP98, but I can tell there is a tiny difference in how well it runs, so choose Shell. I use a number of Shell stations and maybe 10-20% of the time I use the one at Golden Grove. This tankful came from GG. The replacement tankful came from the Shell on Churchill Rd. I have occasionally been suspicious of the operation of the engine after fills at GG. Some fluffiness at idle, maybe some pinging (in fact, I think the tank that caused it to ping like a meth addict last year came from there). That sort of stuff. But only vague suspicions, nothing quite as convincing as last week. Has anyone else had a weird result from there, or any other servo in particular?