Gas vs. Diesel Engine Life

[davahad]

I'm waiting for the X5 Diesel due out later this year and have heard that Diesel engines last much longer than gas engines. Curious what owner's experiences are in this regards and what to expect? Also, is it less expensive to maintain a diesel engine?

Any other pros and cons woud be appreciated.

Thanks.

[JCL]

There isn't any public high-mileage experience with the most recent BMW diesels since they are fairly recent introductions. Assuming that there are no problems with the aluminum blocks, they should have good life, similar to previous generations of BMW diesels.

Older-technology heavy-duty diesels that routinely went for hundreds of thousands of miles bear little resemblance to today's electronic/aluminum block diesels.

In general, diesels have higher compression ratios, resulting in higher peak cylinder pressures, which are a factor in faster wear. That can be overcome with a heavier block casting, but we are not seeing heavy blocks in modern automotive diesels. Diesels benefit from lower piston speeds, which is a factor in lower wear, due to their lower relative speeds compared to gasoline engines. Both these factors are theoretical to a certain extent.

In practice, considering the complexity of the rest of the vehicle, the car is likely to become very expensive to maintain long before the cylinders wear out, exactly the same as with a gasoline engine.

Maintenance cost? High pressure direct injection fuel systems are very similar these days for gasoline and diesel. Diesels have no ignition system, but how much do we really spend on spark plugs these days? Diesels will be less tolerant of water in the fuel, or of cold weather, and will likely require urea to be added during services, but all in, maintenance costs are likely to be pretty much a wash.

[deutsch100]

I've had 2 diesel cars, a 1983 Mercedes 300TD and a 1992 300D 2.5Turbo. The 300TD had 190,000+ miles, and the 300D has 90,000 miles. Diesel engines are much more expensive to manufacture, but cost much less to maintain. From a German standpoint, EVERY taxi is Diesel, due to the much higher mpg, and most German diesel engines go hundreds of thousands of miles.

There are A LOT Mercedes and BMW passenger cars with 350,000+ miles on the original engine (but more Mercedes )

[Quicksilver]

Let BMW speak for themselves......http://www.bmw.com.au/scripts/main.asp?PageID=21935

The latest BMW technology in 6-cylinder diesel engines

The latest 6-cylinder diesel engine from BMW recently made its Australian debut in the 530d and the X3 3.0d. This engine has the latest technology from BMW in the form of an aluminium crank case (previously cast iron) which offers weight savings of around 25kg. It also embraces cast iron cylinder liners which are used to ensure strength and durability. The overall weight saving contributes to improved handling with reduced weight over the front axle, an improved weight distribution over both axles and greater fuel efficiency through carrying less weight.

[jimsaq]

3.0d has been available here for a few years, I haven't been following them closely but haven't heard any horror stories about longevity

time will tell for the 3.0sd which has only been here since about december

[Wagner]

Originally Posted by JCL

There isn't any public high-mileage experience with the most recent BMW diesels since they are fairly recent introductions. Assuming that there are no problems with the aluminum blocks, they should have good life, similar to previous generations of BMW diesels.

Older-technology heavy-duty diesels that routinely went for hundreds of thousands of miles bear little resemblance to today's electronic/aluminum block diesels.

In general, diesels have higher compression ratios, resulting in higher peak cylinder pressures, which are a factor in faster wear. That can be overcome with a heavier block casting, but we are not seeing heavy blocks in modern automotive diesels. Diesels benefit from lower piston speeds, which is a factor in lower wear, due to their lower relative speeds compared to gasoline engines. Both these factors are theoretical to a certain extent.

In practice, considering the complexity of the rest of the vehicle, the car is likely to become very expensive to maintain long before the cylinders wear out, exactly the same as with a gasoline engine.

Maintenance cost? High pressure direct injection fuel systems are very similar these days for gasoline and diesel. Diesels have no ignition system, but how much do we really spend on spark plugs these days? Diesels will be less tolerant of water in the fuel, or of cold weather, and will likely require urea to be added during services, but all in, maintenance costs are likely to be pretty much a wash.

Fully agree

Actual motor to motor, with no car involved, in a bench test...the diesel should almost always out last the gasoline variant. But in the real world, with so many other tangibles....it becomes the idea of better mileage and more torque vs a NA gasoline engine.

[chonko]

Originally Posted by davahad

I'm waiting for the X5 Diesel due out later this year and have heard that Diesel engines last much longer than gas engines. Curious what owner's experiences are in this regards and what to expect? Also, is it less expensive to maintain a diesel engine?

Any other pros and cons woud be appreciated.

Thanks.

I can't say I have owned any BMW diesel product because that will not be accurate, however this is what I know from Diesel engines:

1. The engines last longer than petrol engines because of the low running speed when compared to their petrol counterpart.
2. Diesels are more viscous than pertol and then to provide extra lubrication to the piston chamber thus prolonging the life of the engine.
3. Diesel engines do not require spark plugs and they are easy to maintain as well.

[davahad]

Thanks for all of the replies and all of the good information.