19mpg (US) mixed driving, about 50%-50%. once got as high as 27mpg on a long drive on a hot day at about 3000 feet altitude (Nevada to Idaho), with the A/C on. sedan gets slightly better mileage.

1991 300E, 136,000 miles. I too keep a log and receipts of every fillup, etc. and closely monitor my car's performance. I consistently get 20 mpg in stop-and-go city traffic and 25 mpg on the highway. That said, if I drive very aggressively with the headlights and A/C on, I might on rare occasion get as low as 18 mpg.

Usually in the range of 18-24 depending on the mix of in-town and freeway. High 20s on extended highway trips and have exceeded 30 on a few legs. The EPA estimate for my car is 18/26; 20/23 for the automatic.

A manual trans with its overdrive fifth definitely improves the highway mileage.

You can find the original EPA fuel economy estimates for your make and model at the following web site:

http://www.fueleconomy.gov/feg/bymake/bymanuNF.shtml

Duke

126 car with the small motor gets 23mpg - USA.

I do mostly highway driving and travel at speeds around 65mph.

103 Fuel Consumption
 

I too have been monitoring this closely in a well tuned 89 300ce.

In city driving with AC always on I was getting 12-13 litres / 100km which equates to 19.7 - 18.2 mpg

That was running steadily on Premium Fuel i.e. BP Ultimate.

I had to fill up one day at a station with no premium fuel and used regular. Since then I have used several tanks as the car feels like it is running better??

Fuel consumption is now around 11 litres / 100km = approx 21mpg or better.

In this time I have also had the EHA adjusted drastically improving driveability and performance. It would seem that it was set on the rich side and is now back to stock. I don't think this has an effect at cruising speeds though.

In country driving I see 9-10 litres / 100km = 24/25 mpg.

Is it possible to have better fuel economy on standard ULP rather than premium? This is not what the promotion says.

300e mileage
 

On a recent long (500 mile) trip, my '92 300e 2.6 got 26.7 mpg one way (into the wind) and 29.3 coming home with a really strong tailwind. This was driving 80 mph.

Does the 2.6 liter really get that much better gas mileage than the 3.0?

I also have a '88 260e and get about 26 mpg highway, 23 mpg city. It gets better gas mileage than my 4 cylinder Volvo.

300E 2.8 M104 Engine 25MPG hwy and 21 city
Also if I am using the cruise control on 80mph constant driving for 200miles I get about 27mpg. It is kind of strange that driving at 65-70mph the mileage is around 23-24mpg

I have a '90 300SE.

On the highway, at 70 - 75 mph straight cruising, I net about 22 mpg. If I drive like a jerk, 17 mpg.:eek:

Thus, I try to show respect for the law.

I get 20 -22 mpg, mixed driving ( about 65% highway), in a 88 300ce

I switched our 300's over the mid-grade and saw a slight improvement in mileage. The cars run the same. I was told that the performance may degrade in hot summer temps. We'll see. Premium just doesn't make sense if the car gets better gas mileage with mid-grade. Someone on the board said there was also more energy or some such in lower grades. Go figure.

The only difference in commercial fuel grades for a given region is octane, and you only need enough octane to keep the engine out of detonation. Most M103s will run on lower octane than premium, but detonation tendency increases with higher air and coolant temperatures, so higher octane may be necessary during the summer months than the winter months.

I have seen reports that some lower octane fuel blends have slightly higher energy content, but this is only 1-3 percent, and the effect on fuel consumption would be about the same percentage as the energy delta, so it would be tough to measure.

Oxygenated fuels have lower energy content that non-oxygenated fuels. and the difference in fuel economy is, again, about equal to the oxygen content.
In California we have about 2 percent oxygen (by mass) in our "RFG II" gasoline, year round, which degrades mileage about two to three percent from the non-oxygenated fuels of ten or more years ago.

Duke

Lower octane fuels burn faster and release slightly more energy. In addition to detonation they will make the engine somewhat hotter. I use 89 in both my M103's

And your point is?
 

And your point is? Better fuel consumption with 89, and what is it?

Same here.
 

Have noticed this with my Saab - if I drive constant at 60 mph I don't get as good mileage as if I cruise at 75-80 mph. Wonder why?

Utter nonsense!

Within the range of normal automotive fuel blends there is no significant difference in flame propagation speed for normal (detonation free) combustion.

Duke