The '78 diesel VW Rabbit got almost 50 MPG. WTF happened?

Question

I knew people that claimed they got almost 60 MPG out of them. So; my question is, with THIRTY years of R&D between then and now, why can't they get even CLOSE to what they had then?

Materials research, powerplant engineering, electronics, they have all improved, but the bottom line is still c**p? Automotive engineers are especially encouraged to answer!

Answer 1

I think you're going to like the new VW's coming out this year and next. The Jetta Diesel will approach or beat that mileage. There are versions of the GTI coming as well that may or may not be Hybrids as well as diesels. It's not clear what form they will take. The next generation Prius will approach 100 mpg. It's all a matter of market demand and various laws throughout the world that car makers have to deal with.

Answer 2

There are many cars in EU and Asia that get that kind of mileage  from their cars. The Diesel motor gets at least 30% better MPG then a regular gas motor. The VW Jetta with a TDI motor gets about 50mpg vs the same car with a gas motor that gets 23city and 33 hwy. The problem with Diesel motors in the 70s and the 80s were emissions. Now because of the advancement of Tech and engineering Tech R&D in Europe they very clean and will give the hybirds a run for thier money.

Answer 3

Diesel powered engines do have better mileage than regulars, but I think 60 mpg is a little exaggerated. It is true that we do not see much progress. But back then, cars are very light, with less powered engine, and with no luxury equiped. Today, in order to meet the needs of consumers, cars have more hp, a/c is a must, auto everything, abs, traction control, etc. It's the weight that make these cars horrible on gas.

Answer 4

I'm not an engineer.  This is mainly a guess of what may have happened.

1) In 1978 diesel engines were not as clean burning as they are today(lots of smoke) and therefor were not welcomed by the American Public.

2) The Prius gets 45 MPG highway so we seem to be pretty close to 50.

3) In the 80's fuel became so cheap we no longer needed fuel efficient engines.

4) The 78 Rabbit is a small car.  The low weight allows for a smaller engine that uses less fuel.  Even with high gas prices the public typically wants to buy a big car.   Bigger cars require more fuel.  Automakers are attempting to make the biggest cars operate as efficiently as possible.  That is what has been demanded of them.  We really shouldn't hold them or the engineers responsible.

Answer 5

Check out the kerb-weight:

1978 Golf L Diesel:     845kg

2008 Golf 1.9 TDI:     1400kg

Nuff said.

Answer 6

Cars today are heavier than cars from the 1970s because of all the safety features that are now standard.  Things like crumple zones, collision cages, airbags, etc.

The 1978 VW Rabbit diesel had a curb weight of 2145lbs.  (the VW Golf was sold in North America as the "Rabbit" if I remember right).

The 2006 Volkswagen Golf Diesel had a curb weight of 2910lbs.

That's almost 800 lbs of extra weight, so fuel economy is going to suffer somewhat.