Comparing a VW TDI to a MB diesel is not going to work. Different cars for different markets. If you can afford a MB you can afford the fuel to run it, period. Nobody buys a MB diesel to get 50 MPG. MB's idea of economy is to build a car that will have a real usable lifespan of 20 years or more. With MB you buy longevity. Also, in North America we can't compare MB's new CDI technology against VW's TDI or PD technology yet.
I will compare VW's old IDI diesels with my MB IDI diesel. The MB IDI diesels are superior to every other IDI diesel in every way. Nobody built an IDI diesel as well as MB, not VW, not Pugeuot, not Renault, nobody. MB simply over built those engines and then undertuned them. The engines last because they are understressed. MB always built the cleanest running IDI diesels too.
MB builds heavy luxury cars so the engines are scaled up to handle the weight. An old 240D is as slow as any old VW 1.6L diesel but even it will cruise forever at its top speed without any risk of accelerated wear, and it will do this year after year after year. I don't think we could do this with our TDIs.
A VW TDI engine might last 400K miles, but a VW body will not. A MB diesel engine will last 400K miles and there is a good chance the body will too. I just turned over 100K miles on my Passat TDI. The Passat is holding up well but the body will be junk in 15 years. My 85 300D still has many good years left in it.
The last generation of MB's IDI diesel engine was state of the art for IDI technology. The US spec 98/99 E300 got a 175HP out of a 3L 6 cylinder engine. Performance was 0 to 60 MPH in 8.5 seconds and a top speed is 135 MPH, in a car that weighs around 3,700lbs/1682kg. When driven reasonably the E300 could return up to 35 MPG. Not bad at all for a heavy car with a lot of power accessories.
MB timing chains easily last 150K miles but start to stretch after that. Most AWARE MB owners replace the timing chain between 150K to 200K miles. It's very easy to check the timing chain stretch. I have heard some tragic stories of owners whining about the engine just locking up with over 200K on the original timing chain. Dealer cost of replacing a timing chain is about the same as replacing a timing belt on a TDI.
MB's design philosophy was to engineer the car, and then assign a price to cover the cost to build it plus a good profit. Everybody else picks a selling price, and then designs the car to maximize the profit at the selling price. As has been said here before, you get what you pay for.
Brian, 97 Passat TDI, 85 300D-T
