Hey Everyone!

Recently I was driving a 200KM trip down to Geelong, and for some reason my fuel economy dropped when i stopped to fill up. One tank I'm on 450-500Ks (which i suspect was still too low anyway?) and now its down to 300-350 at best.

I got under her today, checked out the filter/pump and they're fine, cleaned the oxygen sensor while I was at it, and then had a quick look for leaks anywhere in the engine but nothing.

I'm fairly stumped as to where to look next, the obvious causes would not usually apply in such a quick manner? I always use premium unleaded fuel, (even at $1.60 a liter!) and run some injector cleaner through every few months (did run some through last fill up but still at the 300-350Ks per tank...)

Anyone improved economy with any different methods out there? Id be interested because I do usually long distance drives in the 300E, and I really like to keep her in tip top shape.

Thanks in advance folks!

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1971 280SE - The S Class
1974 280CE - Sterling
1988 300E - Stanley