Avoid opening engine before UOA?

[wirelessF]

When planning to do a UOA? I've been planning to change/pull the spark plugs in my truck since I've might have went over the service interval but I've been wondering if it might skew UOA wear readings.

Current fill is Nextgen 5w20 in a toyota truck. Got 3,600/3mos on the oil and plan to sample at 5,000mi. Probably extend to 6,000 or 6 moths max.

 

[gathermewool]

Changing the plugs will not affect your UOA, unless the plugs you're replacing are so worn that one or more cylinders were firing incompletely.

The short answer: not one iota.

 

[Gene K]

I cant even see any difference when I pull the valve cover on my DD60 to run the valves and injectors. Still see Silicon barely above native just like always. Native was 8 ppm in my Rotella T3 on reference sample.