Gas Mileage?
 

I've got a 98 e430 and took it for a road trip over the weekend. I averaged 27.4 MPG on the highway & got almost 540 miles from a tank of gas.... I was impressed, as this is better than my last car a 95 e320...... a V8 that get better gas mileage than a 6...... oh, the car has 56K on it, and I was thinking that around 60 K I would do the spark plugs and the O2 sensor... I'm thinking it may not be time yet.....

Replacing the plugs is a good idea. Your car has four oxygen sensors though, but don't worry about it. The car will tell you (via the Check Engine light) when you need to replace one!

it's got 16 spark plugs..... I didn't know that when I bought it....... 4 O2 Sensors? ouch, thats going to hurt.... I'd still rather do perventive maintenance. I hate getting stranded. In other words, I'd rather do maintenance on my schedule than the car's....

Modern V8s usually have 4 O2 sensors, but only 2 upstream O2 sensors got involved in fuel injection and can affect gas mileage. 2 downsteam O2 sensors are only used to monitor Catalytic efficiency, they only bring up a check engin code/light when CAT efficiency is low.

27.4 mpg is quite impressive, the best gas mileage I got from my 92 400E was 9.5L/100km (24.7mpg) when highway cruising in summer, in winter, the best I can get is 12L/100km (19.5 mpg).

That is impressive. I got 26.1 on the inaugural drive back with my of my latest purchase back from Lexington, KY. Its was an ebay purchase. 97 E420 70,000. I get around 20mpg in the city.