Piston Slap: MKV GTI Daytime Lights: Running Out of Time?

Sajeev Mehta
by Sajeev Mehta

TTAC commentator talkstoanimals writes:

The recent TTAC flap over the Priapus’, er, Prius’ potentially failing HIDs got me to wondering if turning of my MKV GTI’s daytime running lights would lead to any meaningful gains in HID bulb longetivity. Historically, I only tend to keep cars for approximately 80k miles. I also like the fact that DRLs mean I never forget to turn on my headlights in the rain—a requirement in many states in my neck of the woods. However, I like this GTI so much that, the car gods willing, I may keep it longer than my other cars.

So is it worth it to shut the DRLs down and possibly keep the bulbs in action for a longer period of time? Or would the potential gain be so small that it fails to offset the potential for forgetting to light the Xenon fires in the rain? (I never had a problem remembering to turn on the lights before my cars came equiped with DRLs, but I’m not getting any younger and neither are my memory banks.) Lastly, how does one turn off the DRLs in a MK V GTI? My owner’s manual sheds no light (groan) on the subject.

Sajeev answers:

Conspiracy theory alert! When the DRL issue came to “light” (double groan), I thought the battery lobby pushed hard to bring this supposed safety feature stateside. Which worked great in frozen Nordic countries, but has little to no statistical benefit to car accidents in the mostly-thawed US. And demanding more electricity on a regular basis has some amount extra wear and tear on the car’s charging system. Hence my paranoia.

Back to your HID + DRL dilemma. I cruised VW forums and the best way to kill DRLs without hacking wiring (usually not a good idea in a VW) is to buy a European headlight switch, and then reprogram the computer to accept said Euro-toggle device. FAIL: that’s pricier than a new pair of HID capsules, so . . . leave well enough alone.

Bonus! A Piston Slap Nugget of Wisdom:

I’m no Daniel Stern, so when in doubt, I ask Daniel Stern.

“You won’t realize any practical increase in HID bulb longevity by deactivating the DRLs. What is hardest on HID bulbs is turning them on, not leaving them on.

If you nevertheless wants to turn off the DRLs or alter any of the car’s other lighting parameters, it’s done with VAG-COM, the VW computer interface. A Google search focusing on the VW forums will give full info.

As for DRLs in the rain: Sure, but while most VWs turn all the exterior lights on full-time with the DRLs (or have an ambient-light sensor to turn the parkers, markers, and tails on when needed), lots of other DRL-equipped cars don’t, so it’s important not to put too much faith in the DRLs.

In most cases, you still have to turn the headlight switch all the way on when it’s dark or stormy to display low beams, sidemarkers, and taillamps for adequate visibility and safety.”

[Send your technical queries to mehta@ttac.com]

Sajeev Mehta
Sajeev Mehta

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  • Toasty Toasty on Aug 19, 2009
    ttacgreg: Personally I believe if some one is not mentally prescient enough to see an approaching vehicle in broad daylight, a set of head lights won’t matter. Since we're fairly sidetracked anyway... Many drivers may not be "prescient enough to see an approaching vehicle in broad daylight", but what about the wide variety of lighting conditions other than daylight and complete darkness? A major complaint of DRL opponents has been addressed by modulating light output to 30% or so while operating in DRL mode. This solution (or using the forementioned LED solution) seems to address concerns on both sides of the debate. There's a problem with relying solely on statistical analysis to discuss the efficacy of DRLs, or any other safety measure. There are instances where a smart DRL system has been effective, and to those people that avoided accidents, DRLs had a meaningful impact, regardless of the statistical significance. If a smart DRL system is designed to minimize glare, fuel economy impact, production costs, etc., I see it as a net benefit, even if it only has "a negligible effect" on accident rates. There are good DRL systems, so rather than condemn all DRLs, we should support the good ones.
  • Gman37 Gman37 on Aug 21, 2009

    I had the same concerns as the OP for my MKV GTI so I used VAG-COM and use my fogs as DRLs. I could have disabled the DRLs entirely but I like the look of the fogs and they are cheap to replace (bought some Nokya yellows on ebay for 15 bucks).

  • Scott What people want is the Jetson Car sound.This has come up before.
  • Joerg I just bought a Corolla Cross Hybrid SE a few weeks ago, and I regret it. But not for any of the reasons stated so far. It drives well enough for me, gas mileage is great for a car like that, the interior is fine, nothing to complain about for normal daily use. I bought this relatively small SUV thinking it is basically just a smaller version of the RAV4 (the RAV4 felt too big for me, drives like a tank, so I never really considered it). I also considered the AWD Prius, but storage capacity is just too small (my dog would not fit in the small and low cargo space).But there are a few things that I consider critical for me, and that I thought would be a given for any SUV (and therefore did not do my due diligence before the purchase): It can’t use snow chains per the manual, nor any other snow traction devices. Even with AWD, snow chains are sometimes required where I go, or just needed to get out of a stuck situation.The roof rack capacity is only a miniscule 75 lbs, so I can’t really load my roof top box with stuff for bigger trips.Ironically, the European version allows snow chains and roof rack capacity is 165 lbs. Same for the US Prius version. What was Toyota thinking?Lastly, I don’t like that there is no spare tire, but I knew that before the purchase. But it is ridiculous that this space is just filled up with a block of foam. At least it should be made available for additional storage. In hindsight, I should have bought a RAV4. The basic LE Hybrid version would have been just about 1k more.
  • MaintenanceCosts Looks like the best combination of capability, interior comfort, and subtle appearance can be achieved by taking a Laramie (crew cab, short bed, 4x4 of course) and equipping it with the Sport Appearance, Towing Technology, and Level 2 packages as well as a few standalone options. That's my pick.Rebel is too CRUSH THAT CAN BRO and Limited and up are too cowboy Cadillac.
  • Xidex easier to buy a mustang that already sounds like that. love the coyote growl
  • Oberkanone Shaker motor on an EV. No thanks.
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