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I was told the old diesel engines would run much longer than a petrol engine. However, modern diesel cars have turbo's which seems like a component that could easily blow.

I am actually interested in a rough generalized answer, but if the question is to broad I would narrow it down to:

What are the maximum expected km/miles that one can get on a turbo of a well maintained and properly driven VW T4?

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  • "properly driven" = Which ever way one should drive to extend the life of a turbo. I was thinking about asking another question on HOW should one drive to extend the life of a turbo as well, but I guess that should be a separate question on this website. Sorry, English is not my first language. Should I use a different term?
    – Jasper Citi
    Commented Oct 27, 2016 at 6:30
  • You're doing fine - it makes sense but there were two ways it could be taken. Your comment shows its about maximising the life span, and not how long will the turbo last if you "drive it like you stole it"
    – Criggie
    Commented Oct 27, 2016 at 6:37
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    I have posted my second question here: mechanics.stackexchange.com/questions/37979/…
    – Jasper Citi
    Commented Oct 27, 2016 at 7:20

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You've asked a general question that has a few too many variables to answer concretely (e.g., type of turbo, application, environment, maintenance schedules, etc.) I'm going to propose a variant of your original question and answer that:

Is it possible for an original equipment turbo to live as long as the rest of the car?

The answer to that question is: yes, it is possible but not if you're careless.

Let's think about a turbo system at its very highest levels and try to find possible failure points:

  1. Hot exhaust gas spins the turbine blades (can your exhaust temperatures exceed spec, e.g. due to a bad tune?).
  2. The shaft connecting the turbine side to the compressor side spins incredibly fast (bearings properly lubricated? Using what source of oil? Are the bearings cooled via another mechanism as well?)
  3. The compressor side compresses the intake air (is the intake air well filtered? Is there any other possible material that could get into those blades and chew them up?)

Those are some obvious ways to break a turbo. However, there are no magic spells. It's possible that your particular turbo will have an engineering flaw that breaks some thousands of miles before the engine falls out of the car. You can only work the variables under your control.

On my car, for instance, I have 180K miles on the original turbo. I have a good air filter and have removed a piece of the piping that has been known to fail and get chewed up in the turbo. I watch my oil consumption and let the engine take a cool down lap after boost (a relaxed drive through the neighborhood does wonders). While this might not prevent all possible failures, it has certainly avoided dumb failures that I can prevent.

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    Would this answer vary between a diesel and a petrol engine turbo? Suspect not, the turbo shouldn't care what fuel made the exhaust gases.
    – Criggie
    Commented Oct 27, 2016 at 18:55
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    @Criggie at this level of detail, no. If you really want to get super granular, you should be talking details of a specific vehicle. I tried to keep things casual for this exercise, though, and provide decent useful guidelines for a non-expert.
    – Bob Cross ♦
    Commented Oct 27, 2016 at 19:33
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    For what ever it's worth we have two VW TDI diesels with over 250,000 miles on the original turbos. I've had more problems with the turbo controls than with the turbos themselves.
    – dlu
    Commented Oct 28, 2016 at 23:12
  • I have heard of anecdotal failure prevention methods that deal with "spool down" which is allowing the turbo to slow down with the engine idling thus providing lubrication or use of an oil accumulator which essentially stores oil under pressure that bleeds down through the turbo after the engine is shut off maintaining lubrication as the turbo slows down. Another issue was coking of the oil (baking it to carbon) in the lines eventually blocking the flow and leading to bearing failure.
    – mikes
    Commented Feb 8, 2022 at 22:38
  • @mikes, I'm not sure what you mean by spool down. The turbo is going to spin down right quickly as soon as there isn't an excess of exhaust energy for it to ride on. If you mean letting the engine idle after reaching your parking spot, yes, this was a practice on older turbo cars. This would keep oil flowing past the bearings while dissipating heat from potentially quick hot spots in the turbo.
    – Bob Cross ♦
    Commented Feb 10, 2022 at 1:36

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