Depends on the type of spark plugs. Factory plugs around 70 - 100k depending on the condition of the plugs. I would replace the spark plugs out with some AC Delco iridium plugs they will last you 100k+.
How to change the spark plugs
Change the plugs at 100,000 miles or earlier if the engine is not performing as it should.
According to the owners manual, they have platinum plugs that should be changed at 100,000 miles.
If they are platinum plugs, should be every 95,000 to 100,000 miles.
At 100,000 miles or 160,000 kilometres you change the spark plugs. www.trailvoy.com All the answers for your Envoy/Trailblazer from true enthusiasts!
ac delco spark plugs are type that originally came with 2003 GMC envoy
The original plugs should be good for around 100,000 miles ( 160,000 ) kms. Take it from there.
Change the plugs and wires at 100,000 miles unless you experience poor performance or a drop in MPG. In that case change them sooner.
Generally I change platinum plugs at 100K and regular plugs at 50K.
AC Delco Iridium spark plugs.
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