Piston Slap: Vee-Dub Sludging While Hypermiling?

by Sajeev Mehta

Published: June 1st, 2009

piston slap vee dub sludging while hypermiling

Stewart writes:

The Jetta sludge issue had me wondering. I hyper-mile my 2003 Jetta TDI 1.9L which, of course, has a turbo. [Side note: if anyone wants to tell me what an idiot I am for mooching along at idle in 5th gear to get 70MPG, feel free to tell me why that’s bad. I am exquisitely sensitive to all the Type A drivers (going 15 MPH over, screeching to a halt at the next red light) and let them go by safely.] I change the oil every 5K miles with the recommended Castrol from the VW dealer. Here’s my question: I make my change just after a run of at least 20 miles and I use a suction pump to get the old oil out, a Pela PL-6000. I’m wondering if, by not draining the oil out the crank case plug, will I have sludge buildup in my Jetta?

Sajeev answers:

Mooching is fine, but I’d worry about unnecessary engine load in your fifth-gear-at-idle scenario. Maybe pop the Jetta out of gear and coast to more stops instead? It’s been debated before, and I still think coasting is better than staying in gear simply because you maintain higher speeds for longer time, keeping the numerator of the miles/gallon equation quite happy. Coasting is even better on cars that roll effortlessly because they are light on engine braking.

Back to the sludge:

Given the quality of today’s oils and the stellar reputation of the TDI, I doubt sludge is a big problem for you. Even if I’m wrong, at your oil change intervals, whatever sludge accumulated is small enough to suck through the Pela’s plumbing. My only concern with “sucky” oil extractors is where the tube rests: they won’t pick up all the old oil unless it by the drain plug. Unless you can see the tube when you remove the drain plug (good luck with that) can you be certain you’re getting all the old oil out?

Aside from that assurance, I use the drain plug (or plugs on dual sump systems) for oil changes so I can do a visual on mechanical bits I can’t see under the hood: check for leaks, inspect pulleys, poke a bushing, clean radiator fins, etc. That’s less important on newer cars, but your six-year-old Jetta is no spring chicken anymore.

Overall, I think you have nothing to worry about . . . unless the B&B says otherwise, of course.

Sajeev Mehta

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Chuck Goolsbee on Jun 01, 2009

The 1.8T is the known sludger in the VW engine lineup. The 1.9TDI is not. Turbos on gassers run a lot hotter than those on Diesels. The intake clogging on TDIs can be prevented by replacing the factory MAS with an updated one, specifically part # 0281 002 757. It is literally a 3 minute job requiring a screwdriver and a pair of pliers. I highly recommend the procedure. Otherwise plan on spending a full day prone atop your engine getting the intake off to clean it. As for oil, my TDI is an earlier one so I don't have to blow big bucks on exotic synthetics. I just use Delo or Rotella, and change my filter every time I change oil. I have a lift in my barn, so I always do it out of the bottom with the drain plug. I also let it drip out overnight... because I can. Like the others have said, I like the contemplative time under the car looking up at it. Gives me a chance to check for other issues and be aware of the car's overall health. --chuck

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Brettc on Jun 01, 2009

As others have said, the TDI doesn't suffer from sludging problems like the turbo gas engines. However, if you're lugging it in 5th gear a lot, you probably need to have an intake cleaning done. My 2003 Jetta TDI is at about 107000 miles, and I cleaned my intake about a month ago. It was hard to comprehend how much gunk was clogging it. And after cleaning your intake, do the EGR adaptation via VAG-COM. I have two questions for you. Why are you changing your oil every 5000 miles, and why are you going to the dealer to buy Castrol oil? The oil change interval for the ALH TDI engine is 10000 miles. Any VW 505 00 compliant oil will be fine, which means you have your pick of Mobil 1 European formula (0W40), Mobil 1 Turbo Diesel-Truck (5W40), or Rotella Synthetic 5W40. All 3 of these oils are available at Walmart and other auto parts stores. I use a Pela extractor to change my oil. I've only done it via the drain plug once before I bought my extractor. I put it up on ramps every once in a while and check things out, but I find there's no need to take the belly pan off and drain it via the plug, unless you love laying on your back.

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