Yeah, people assume the 400E / E420 gets much worse gas mileage than the six cylinders, but the decline in mpg is only 1 mpg less, both in city and highway driving.
And I agree with blackmercedes, I think the 400E / E420's are the best of the W124's. The 500E / E500's are obviously worth more and are faster, but considering value for your money, you can't beat the 400E. You're getting 85% of the performance a 500E at less than half the price. And the premium of a 400E is only about $1k more than a similar year 300E / E320.
2001 E430, Bourdeaux Red, Oyster interior.
1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".