Hello everybody

I have just bought a Mercedes-Benz 260E (W124 series), European Sportline model, in very good shape(the car is from 1990), with 97,000km(about 60,300 miles) on the odometer.

The sole problem is the fuel economy - MB gives 14-16 liters per 100km (16 to 14 mpg, roughly), yet in city traffic it took up to 23 liters / 100km (10 mpg, for our American friends).

What can cause the problem? Faulty oxygen sensor or clogged air mass sensor can give a false signal to the ECU and "ask" for more gas, but shouldn't the idle increase and the engine operation become erratic? The engine works just fine, at all rpm ranges, and no warning light comes on.

There is an economy indicator on board, yet I've not revved up the engine until it shows "high". How is the device wired, and which gas flow does it indicate - at the fuel pump or at the injectors?

~Thank you

Nautilus

PS I've changed the oil upon purchase, and put 10W40. IS it suitable?

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1990 260E Sportline (that's 300E 2.6 for our American friends) -> sold
2001 E320 4Matic Elegance -> my Dad's daily drive
2005 Seat Leon FR 1.8T