Is synthetic blend oil in over 200,000 miler TDI good or bad or indifferent?

norbert77 said:

What is this oil life sensor, is it magic?

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Almost.
Not sure how the VW system/sensor works but in the wife's former Cadillac the system monitored number of starts (cold and warm) operating temps and load, as well as other data. I doubt it tested the acidic content but I think the VW and other new tech system sensors actually monitor chemical changes to advise when a change is needed. Or...just change it on a normal extended interval.

SRHeer said:

I have a 2001 Beetle TDI and needed to change oil so all I had quick access to was a Valvoline Heavy Duty Diesel 15-40 Oil now I changed the oil filter like I always do but should I be concerned about using this instead of the Rotella 15-40 fully synthetic diesel oil that I usually use?

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thought synthetic was required in turbo cars because regular oil cokes up in the turbo after you shut down the car. Since the turbo is extremely hot, when oil circulation stops the oil literally burns and turns to carbon.

True. But thats from shutting it down immediately after driving hard or longer highway driving. In those situations, just let it idle for a few minutes. If you’re just driving the car normally or even gently, you don’t have to worry about it at all. Plus, compared to a gasser, diesels idle burning barely any fuel, so there’s barely any heat in the exhaust. Actually, isn’t diesel exhaust generally lower temp than gasoline?

15w40 isn't good for a TDI. You should run 5w40 synthetic that meets VW's 505 spec. Easy to find. When TDIs were launched they didn't recommend synthetic, but they had issues with piston rings coking and jamming, so they switched the recommendation to synthetic.

Zak99b5 said:

True. But thats from shutting it down immediately after driving hard or longer highway driving. In those situations, just let it idle for a few minutes. If you’re just driving the car normally or even gently, you don’t have to worry about it at all. Plus, compared to a gasser, diesels idle burning barely any fuel, so there’s barely any heat in the exhaust. Actually, isn’t diesel exhaust generally lower temp than gasoline?

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This is really a non issue on TDI's as the exhaust temps are simply not hot enough to cause the oil to coke on the turbo. I have pulled apart plenty of abused ALH engines and never seen one with a coked up turbo or rings.

IndigoBlueWagon said:

15w40 isn't good for a TDI. You should run 5w40 synthetic that meets VW's 505 spec. Easy to find. When TDIs were launched they didn't recommend synthetic, but they had issues with piston rings coking and jamming, so they switched the recommendation to synthetic.

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I'm not going to say that I'm right, or that you're wrong, but I will say my Alh will hit 420k this weekend, ran for right around 200k on 15w40, dino oil at that.

ghohouston said:

I'm not going to say that I'm right, or that you're wrong, but I will say my Alh will hit 420k this weekend, ran for right around 200k on 15w40, dino oil at that.

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15w40 in a tdi is probably fine in the TX climate. Wouldn't recommend it here in the Northeast. Or anywhere that sees regular snowfall in the winter. The starter in my 7.3L Ford sure didn't like it when temps got well below freezing.

I would agree with that. The freak occurance when it got down to I believe 0 degrees here I think 2 winters ago, it definitely was cranky, but did start. I'd also like to state I've been doing 10k oci's as well as long as I've had the car. When I pulled the cam at 371k (due to a timing belt tensioner failure) it looked great, as did the lifter tops, and they were all original.

And I've personally witnessed in the cold how much better a 7.3 starts with 5w40 vs 15w40. I had 7 out of 8 gp's go bad on my 2002 back when I had it. It killed the starter as it started to get cold that winter. I then swapped to 5w40, as an oil change was cheaper than buying new glow plugs, and there definitely was a difference. At the same time, h.e.u.i. injection is a completely different injection system, that I'm sure you know uses the engine oil to fire the injectors, so I'd say in a real cold climate, 5w40 would be more important in a 7.3 than an Alh, or anything mechanically injected.