I used to be super impressed with overseas diesels until I learned the difference in an imperial gallon and a US gallon. There is a considerable difference. Also the cost of diesel per gallon is much higher than gasoline and offsets the 10mpg better fuel economy.
1 imperial gallon is 1.20095042 US gallons.
If you calculate the 50mpg in the US, it is a womping 60mpg in the UK!
For a gas burner, that is really good.
Now for US diesel.
I drive a Prius. Average fuel economy for 169 fill ups is 41mpg (49.238944137UK).
Lets look at the nice Jetta TDI. They get an average of 45mpg (54.042743564999995UK)
With Gas prices at $3.499 and Diesel at $3.799, there is a $0.30 hike in fuel cost per gallon.
If we calculate the difference we come up with:
Cost per year driving 25,000 miles (I drive 25k-30k per year)
Diesel 45mpg @ $3.799: $2,106
Gas 41mpg @ $3.499: $2,128
Even though it gets 5mpg better economy, it only saves $22 per year. Not a huge savings, and diesel uses more barrels of oil to produce. Only 12.7 barrels of oil are used to produce the needed gas, and 14.3 barrels of oil are needed to produce the needed diesel for the same 25k miles.
Another argument is the cost of maintenance. Both vehicles are pretty costly to maintain. Prius batteries are expensive, costing $1500-$3000 for a rebuilt battery. On the other hand, the diesels use high pressure fuel systems. Injectors are expensive and so are fuel pumps which can also be in the same $1500-$3000 range.
I hope this helps the confusion.
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