Forget MPG ... Best Long Term Option 50i or 35d

[4MoJoe]

I had the 'old' 3.0i, 4.4i and now the diesel. My 3.0 gave me less headaches than my well cared for 4.4i did but the V8 gave me more smiles. However, at the end of the day the constant repair issues of my 7 year old 4.4i broke the deal. I couldn't depend on it (and I may have been one of the few that is just kept nailing me to the wall on repairs).

I bought my x35d with significantly less options than I had wanted but really it's quite adequate for me; a V8 was not on my list because of past experience. But I think you'll have fun with either vehicle.

[David Mc]

V8's are fun, but everything that is expected to work and last is diesel - large trucks, tractors, trains, heavy equipment. The reason is simple, assuming proper routine maintenance (i.e. regular oil/filter changes and clean fuel), the answer to engine longevity comes down to getting the highest possible engine torque at the lowest possible rpm, using the least amount of moving (and therefore potentially wearing) parts. If BMW had released the X5 with their V10 engine and I were to vote for the V10 in preference to the V8, it would be purely on the basis of fun to drive factor. Sorry guys, but based on reasoned logic, my vote has to be for the diesel.

[JCL]

Originally Posted by Quicksilver

Seriously:
Your saying "A far better comparision to an automotive diesel would be the Oldsmobile V8, with the diesel that was made out of a gasoline engine. That didn't work out so well. Or consider the Smart diesel." Are you comparing BMW diesels to Oldsmobile V8 diesels? If so (I'm no expert) but I find that hard to believe...

I don't think a BMW diesel is much like an Oldsmobile diesel. But it is more like that engine than it is like a 15 litre medium duty truck diesel in a Kenworth, which is getting broken in at 80,000 miles. Automobile engines have more in common with each other than they do with much heavier truck engines.

[diesaroo]

Due to all the modern engine complexity, hpfp and others, and increased engine output, I would be very careful to say either way which would last longer. I think all modern car engines' longevity pale in comparison to their forebears.

Your particular vehicle with its particular set of circumstances would likely be a larger determining factor in determining longevity.

For instance, if you do alot of short trips (which isn't good in general) the V8 would be preferable to the diesel since it takes longer for the diesel to reach operating temperature and burn off the condensation in the oil.

Do you have an excellent fuel supplier for gas (low to no ethanol good qc) or diesel (high cetane, no contamination, high turnover)?

Are you an aggressive driver that demands fast acceleration from you car, or are you content to cruise with the torque?

As others have said, pick the one you like the most and if it doesn't last quite as long, that'll be ok too...

Reminds me of my purchase process in buying the 35d. I was intially torn between the ML320CDI and the bimmer since the benz engine uses a duplex timing chain and the BMW uses a simplex. In the end I liked the way the 35d drove better, so I bought it.

Enjoy your life and your purchases and don't worry too much about absolute longevity.

[BGM]

Here is the data supporting (or not supporting) long-term durability of those 2 motors:

1) 35d: None
2) 50i: None

What we do know:
1) Non-aspirated I6: BMW's bread and butter and is bullet-proof
2) Non-aspirated V8: Not as reliable as I6

[Matt_UKTX]

Honestly, I don't think you could go wrong with either. There will be many other components that are likely to fail long before either of these engines does.

[JCL]

Originally Posted by BGM

Here is the data supporting (or not supporting) long-term durability of those 2 motors:

1) 35d: None
2) 50i: None

What we do know:
1) Non-aspirated I6: BMW's bread and butter and is bullet-proof
2) Non-aspirated V8: Not as reliable as I6

Agree with your conclusion, but let's call them naturally aspirated, as compared to forced induction.

[140.6]

Originally Posted by BGM

Here is the data supporting (or not supporting) long-term durability of those 2 motors:

1) 35d: None
2) 50i: None

What we do know:
1) Non-aspirated I6: BMW's bread and butter and is bullet-proof
2) Non-aspirated V8: Not as reliable as I6

Not sure I completely agree with the "None" for the 35d. My understanding is that the M57 engine in various incarnations has been around for awhile. I will grant you that it has not been around nearly as long as various iterations of the I-6. At then end of the day I think Ard had it right early in that BMW has the numbers that would support a more accurate conclusion but the public is not likely to ever see those numbers.

So it looks like I will be making my decision based on "smiles per gallon." In which case I think we can all see where this is headed, I'd place the odds at 3:1 for the 50i at the moment and trending higher.

[Penguin]

I'm surprise no one has mentioned the diesel's SCR exhaust fluid injection system. This is rather new, and was introduced first for the U.S. market, e.g., no long term real life experience at all, unlike the basic diesel engine design where BMW has been selling many diesels in Europe for many years.

I expect that the newly-designed SCR system introduced for the first time with the U.S. diesel has the most risk for long-term problems vs. the V8.

[Matt_UKTX]

Again, I reiterate what I said before... There are many other components on these cars that will fail YEARS before their engines do... Pick whichever you like best, there isn't enough data to make an informed decision either way.