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How dependable is the twin turbo engine in the 2015 435i?

ASKED BY:

​Tim Bromley

FSC MEMBER:

Yes

CATEGORY:

Maintenance

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Question

Hey Gil,

How dependable is the twin turbo engine in the 2015 435i. I have one with about 13k miles and I’m just wondering what to expect after my warranty is up and free maintenance is gone. Any electrical issues? Any turbo or oil consumption issues to be concerned about?

Answer

Hello Mr. Bromley, I’ll try to make this answer as straght forward as possible, but it will get a little technical. Just about all engines today will go to 300000 miles, the more appropriate question is how much will it take to get there. Some engines will require more maintenance than others due to things like design, purpose, etc… Your engine being one of them. I like to say that engines don’t usually “die”, they are murdered, with the lack of proper maintenance.

There is a big discussion in the industry now about factory maintenance schedule and how the manufacturers have been extending the service intervals but the fluids and materials have not really evolved to their requirements. It’s such a long winded topic that I’ll leave that for another time. Just know that their schedule falls short of what you should actually have done to the car if you plan to own it long term. First, oil changes should be done at 5000 miles or 6 months, extending the oil change by only having it done when the car’s maintenance monitor says so will come back to cause issues later. I have had lab tests done to oil from different cars (high quality German oil, not the cheap stuff) and it shows that at that interval the oil is well within it’s usable life span. As an example my wife’s 2002 BMW 530 has 189000 miles and passes an oil lab test with flying colors, which means that there is no wear in the engine. I can go over all of this in detail but to keep this more succinct I’ll refer you to Mike Miller’s old school maintenance guide, it is very detailed. He’s the tech writer for Roundel magazine, you can get the latest version by emailing him at techtalk@roundel.org.

There is another very important item on your car and most newer engines. It uses a fuel injection system called Gasoline Direct Injection or GDI. The main difference is that this system injects the fuel directly inside of the cylinder as opposed to the intake manifold as it is with “traditional” Multiport Fuel injection, the issue is that now the valves do not have fuel going through them and the fuel is what kept them clean from carbon build up. We have seen a very large amount of failures, specially with turbocharged engines with this design. I have spoken to Bosch engineers about it and they said that this is an inherent design flaw and there is nothing that can be done at a design level to change this, the answer is proper maintenance. In this case the issue is a buildup of carbon on the back of the valves and a buildup of oil based residue inside of the intake manifold. There are 2 ways to handle the issue; the first and most widely used is the removal of the intake manifold and you blast the intake ports in the cylinder head with walnut shells. This service is very time consuming and therefore expensive. The other solution is what is called an “induction service”, this type of service has been around for many years and there are a few ways to accomplish it, but it basically involves spraying a cleaner into the intake manifold as the engine is running, the chemical combined with the heat from the engine will “burn off” all of the residue. The problem with GDI engines is that the buildup comes from oil and not fuel, therefore, the most chemicals in the market today will not be effective. There is one company, called BG Products that makes an induction service for GDI cars, they do not sell to the public but any good shop will have access to it, BG recommends that the service be performed every 7500 miles, it should cost in the neighborhood of $100.00. It is the only chemical solution that I know of at this time. The other important item is the fuel, make sure that it is 93 octane from a higher market gas station, Mobil, Shell, Chevron, etc… There is a chemical difference between the fuel from those brands as opposed to lower tier brands, avoid discount club gas stations at all costs, the fuel quality is usually terrible.

In closing, if you keep the maintenance up to date you should be very happy with the car. Also you may want to look into a reputable extended warranty company, a policy from them will invariably save you money during the length of the policy, repair to items like a/c and suspension can get expensive very quickly due to the price of the parts alone.

I know the answer is not short but I hope that it informs you. If you have any questions please feel free to contact me.

Thank you.,
Gil Neves

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This Post Has 3 Comments

  1. Hey Gil,

    Thank you so much for your lengthy and very detailed answer to the question I posed about maintenance. Great information about the BG product and oil change interval.

    I need to find a good independent mechanic as near as I can find assuming the dealer will not perform the BG engine cleaner for the valves.

    One other question I have is related to having oil changes out of the scheduled “10k” or once a year service prescribed by BMW. As I’m still under the free maintenance program. If I have my oil changed I can’t let them reset my computer or it will not register correctly for my free oil service interval. I still have another year but I’m going to start having it changed as to prescribe at 6 month intervals. I only have managed 13k miles since new on my 2015 435.

    You mention having an extended warranty – is that something you would recommend I purchase from the dealer?

    I really like my car and I want to do preventative maintenance as you recommend. I’m glad to hear that it will go 300k miles. I don’t think I’ll ever hit that but I’ll try…

    1. Do you have a recommendation for a good independent BMW mechanic near TheVillages, FL.
      Thanks a lot for your help. You are a great resource.

    2. Hi Mr. Bromley, there are a lot of dealers that use BG products, so your local dealer may be able to do it for you, you likely will have to ask for it specifically as it is a very new product on the market.
      I have a customers that are on the BMW maintenance plan, we just perform the oil changes or other services needed and do not reset the maintenance reminder.
      As far as the warranty is concerned, you will have to do your research on the companies, a lot of them are not reputable, a Google search will reveal a lot of information but an easy way to know if it’s even worth your time is to know how they handle the claims. There are two ways, first they can give a shop approval over the phone, they are the best to deal with. The second if they will send out an adjuster to verify the diagnosis of the shop, stay away from those companies, they try their best not to pay a claim, your car usually has to be at the shop for 2 to 3 days waiting for the adjuster and that person has the final say.
      I’ll contact you on Monday with some referrals for your area. Thank you.

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