I own a 2018 Subaru Outback, 2.5L engine with 48,000 kilometres on it. Subaru recommends changing the spark plugs at 100,00 kilometres or five years, whichever comes first. I can understand specifying a time interval for fluids which degrade over time regardless of whether the vehicle is driven, but I can’t understand why time should be a factor for spark plugs. A search on the internet suggests that over time galvanic corrosion between the steel spark plug threads and the aluminum cylinder heads could make removal of the plugs difficult but the anodic potential difference between steel and aluminum is so small I can’t see that being an issue.
The cost of spark plug removal is substantial (around $1,000) because of the amount of shop time required, so I’d prefer not to do it unless necessary. Thoughts? – David S.
Preform an internet search for Ford pickup spark plug breakage and read decade-old scary stories of cab-off engine repairs because of a simple broken spark plug. While no longer a huge issue for Ford, it put a chill in the air so to speak when thinking about spark plug intervals.
Manufacturer maintenance literature at the time then changed to recommend removing and lubricating at spark plug half-life intervals to prevent seizure and breakage. Which in my mind was silly because if one is forced to spend labour dollars accessing spark plugs to lubricate them, then why not just change them at that time. You are in the same sort of situation as the manufacturer must make these recommendations just in case things go wrong when you haven’t changed them at the five-year interval.
As you noted, the labour is significant to replace the spark plugs on your model because their placement is low in the engine bay. It is this awkward placement that causes technicians to get frustrated and potentially break the spark plug when their tool is not aligned properly. This can happen on both the removal and the installation. This, however, is irrelevant to spark plug age.
In my shop, we work on a lot of Subarus and I can’t remember the last time we broke a spark plug because of it being seized. Sure, they are often tight, but not so tight that a little bit of patience can’t get them out. It’s your call obviously as I would hate for you to be put into the I-told-you-so dealer situation, but I wouldn’t panic to get them done right now.
Lou Trottier is owner-operator of All About Imports in Mississauga. Have a question about maintenance and repair? E-mail globedrive@globeandmail.com, placing “Lou’s Garage” in the subject line.
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