Quote:
Originally Posted by KnudsonsM3
A diesel will ALWAYS be better for towing. Anyone who says otherwise is ignorant. The low end of the diesel and massive torque coupled with the better mpg while towing make gas engines look obsolete.
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That is an ignorant statement, IMO.
Low end torque is good for towing. A turbocharged direct injection gasoline engine has good low end torque as well. Torque peak on the 35i obviously isn't as high as the 35d, but it comes in at a lower rpm on the models I checked. And the torque band is much wider, meaning less shifting.
The peak torque number that matters is at the wheels, also known as rim pull. Engine torque is a good starting point, but that is why we have transmissions, to create rim pull. Flywheel torque is good for winning magazine comparisons though.
High diesel mpg is a good starting point, but an economic analysis will include the local cost of diesel fuel, and the higher purchase price of the diesel. I can make the economics work based on my local fuel prices, but given that the breakeven point is around 80,000 km without even considering the time value of money, it isn't a very attractive investment, towing or not.
Finally, diesels typically have little retarding capability unless they are fitted with an exhaust brake or similar retarding device. Basic science, and very important for towing any significant weight. Not sure how the latest BMW diesel performs here (I haven't towed with one) but it is a point to check on if you live near hilly areas (and if you don't, why would torque matter so much?).
I think port injected naturally aspirated engines look obsolete. The use of the Otto cycle vs the Diesel cycle doesn't dictate which one has direct injection and turbochargers these days.