Differences between gas and diesel?

[Bill K]

I admit to not knowing much at all about diesels so here's my question:

My wife has a 2009 X5 with the gas 3.0. We want a new 2015 X5 with diesel due to the increase in MPG. We've never owned a diesel before so I have some basic questions. 1) does it take the same oil/filter as the equivalent gas model? Same for coolant/water pump/thermostat? Is the only difference (maintenance wise) that the diesel has no spark plugs, but glow plugs that need to be changed and obviously the gas is different. Is there more maintenance required for the diesel, ie, fuel pump, filter?
Also, is there a safety in the filler to prevent the use of regular gas?
Sorry for the many questions.

[JCL]

There are far fewer differences than there used to be.

The gas isn't different, the fuel is different. Fuel pump nozzles are different sizes.

No spark plugs, but some additional items, I'd call it a wash on maintenance costs. Owners have reported more frequent oil changes on the diesel models as called for by the condition based monitoring system; that is likely due to contamination of the oil with combustion byproducts. The diesel uses a different spec engine oil than the gasoline model. The component parts may be different due to the different engine model, but they are similar in concept. If you want to check specific part numbers go to realoem.com and look up the two models. The prices shown won't be exact, but they will be indicative.

Diesels can be more sensitive to water in the fuel; with clean fuel it may never be a problem but if you get a tank of bad diesel fuel every now and then you will be doing fuel filters more often than with a gasoline model.

Early X5 diesel models had some issues with the pollution control system (DEF), mainly due to first adopter issues. Seems more reliable now. Similar issues that gasoline engines had when they got new and more complex pollution controls years ago.

Before you jump, recommend you do a basic cost analysis on diesel fuel in your area. The better mileage is an obvious plus. However, depending on the price of diesel you may not see any savings. When I have analyzed it, it has taken in the order of 80,000 km to 100,000 km to break even, because we have more expensive diesel fuel than some areas. Diesel is the same as #2 heating oil, so is subject to seasonal price fluctuations when it is furnace season. For resale, diesels are not trading at any higher price here compared to 35i models, so the original purchasers took a hit on depreciation (the 35d was a $4500 option). If diesel fuel is not relatively expensive where you live, and you can get a vehicle priced similar to a 35i, it can make a lot of sense.

[Quicksilver]

+1 what JCL said,

However in addition to the questions you asked why not go drive one several times to see if the driving experience is any different.?

[Bill K]

Thanks JCL. In my area diesel goes for abou $3.85 while super runs about $4.10. Since BMW recommends a minimum of 91, the fuel price is a bonus along with the mileage. When you say water in the fuel and filter replacements, are the filters easier to change since it might be done more often? Also, I've been using Mobil 1 0w-40 for my wife's current X5. Can I still use the same oil (when the warranty expires)? If there's water in the tank, is it ok to put a few bottles of gas dryer (that yellow bottle stuff) or will that harm diesel?

[Bill K]

Also, are glow plugs a regular maintenance item, if so how often?

[JCL]

I have read that glow plugs are a 50,000 mile item but can't guarantee that. Call it the same as spark plugs.

If your diesel is cheaper than gasoline that's great. Is that the summer or winter price?

Changing filters is the same as the gasoline version.

You need an LL-04 oil.

If you are leaving the vehicle stored you can use special diesel fuel stabilizers in the tank.

Don't overthink it.

[motordavid]

An interesting Thread on gas vs diesel, from the auto section on City Data Forum...

Some of the posts, esp later in thread, are the usual arm wrestles, but there are some very thoughtful opin posts with pros & cons, need for, rationale, etc, imo.

No dog in this fight, but Bill K may find the opins in this thread food for thought.
GL, mD

The more I read about Diesels... - Automotive -Sports cars, sedans, coupes, SUVs, trucks, motorcycles, tickets, dealers, repairs, gasoline, drivers... - City-Data Forum

[Quicksilver]

Looked at the City Data Forum... and IMO it still boils down what someone wants to drive.
Prius vs VW vs Audi. One thing I can agree with is who want's to drive a boring Prius or a another 2 cylinder egg beater just to save fuel. I want a driving experience. So please someone tell me is there a difference in the driving experience gas vs Diesel?

[JCL]

Originally Posted by Quicksilver

I want a driving experience. So please someone tell me is there a difference in the driving experience gas vs Diesel?

I think there is. The diesel revs low, and uses its torque. The gasoline engine (now that it is turbocharged) can also rev low, with lots of torque but not as much as the diesel, but it can also be run up through the rev range.

Some don't mind the diesel engine characteristic at all. I purchase BMWs partly for the sensation of running a straight six engine up to (less than) redline regularly. I would miss that with a diesel.

I have owned two diesels (not BMW), and they were fine. A bit of a nuisance to refuel, but fine. Good mileage. Just not as engaging as a free revving gasoline engine is.

I tried to make a diesel X5 work in an economic analysis, but couldn't given my local fuel prices. I still like the F15 diesel because it comes with the stronger version of the ZF 8HP transmission than the 35i, but that only matters for heavy towing.

Everyone will have a different version of the above. You've got to drive it and see the difference.

[Bill K]

Thanks for all the comments. Honestly, for me I'd probably pass on a diesel. I drive a 95 M3 and an '11 M3 convertible. This is for my wife who finds the bells and whistles entertaining. Going from a regular gas 3.0 to a twin turbo diesel will definitely be a thrill from 0-60 and certainly a noticeable improvement. Currently, she does about 80%highway driving and averages about 22mpg. Diesel is about 10-20 cents cheaper around here so the savings should add up. I was also always told that a Diesel engine would outlast a gas engine. We typically like to keep cars a long time so she understands this will have to last her at least 10 years till the next car.
To add, we just got back from a European vacation and found that gas over there runs about $10/ gallon. It seemed most people drive a car with a tiny engine (I think I actually saw a bmw 516....a 1.6 liter 5 series?) or a diesel. This presidents mentioned before that we should be paying the same as Europeans for gas, and it appears that we're being styled more and more so like Europe so preparations for future high gas prices seems logical.

I forgot to add that her commute is about 90 miles round trip and we take her car for any significant road trips. So the car will get lots of miles racked up. The extra MPG attained would quickly add up. I think the extra cost for the diesel was only about $2500