Harbor freight compression tester?

[Smoker]

To buy or not to buy? I did a quick Google search and found advice both ways as usual. Figured I'd check with you guys specifically.

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[vanbcguy]

Most folks say it tends to read a bit low.  The real purpose of a compression tester though is to track changes over time and to identify differences from one cylinder to the next.  It'll do those things just fine.

[ORCoaster]

They make several kits so be careful in comparison shopping.  I have one and it seems to do fine.  Like is said, for comparing across the engine and approximate values only.

[Smoker]

Thanks. That was my thought as well... that a compression tester is meant to show major problems, not extremely precise numbers. I think I'll grab one.

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[TimpanogosSlim]

indeed, it seems ok but test it against pressure gauge you trust perhaps?

[Wayland]

I bought one off ebay, but as far as I know, it's the same as the one HF sells. I have used it several times, and while I have nothing to compare it to, the results have always seemed believable. It seems like a decent quality tool.

[vanbcguy]

My understanding is that the reason they tend to read low is due to the volume inside the adapters rather than any issue with the gauge itself.  23:1 compression means the volume of the adapter itself is fairly substantial so it will cause a lower "apparent" reading than a different gauge with less space inside the fittings.