I have noticed a "slight" engine knock on cold start that goes away after a few minutes. It's a deeper knock than the usual lifter noise. It reminds me of the old "piston slap" engines use to get years ago on cold start. My X has 25k on it(3.3L V-6). This winter I decided to keep 10W-30 in the engine instead of running 5W-30. I did this based on my owners manual which states that 10W-30 or 10W-40 may be used in the ambient temperature is above 0 degrees F. Since I live in Tucson, this doesn't appear to be a problem. The temperature has taken a dip though to just under 32 deg F this past week. This is when I noticed the knock had started. I'm wondering if I should switch back to 5W-30 for the winter???

Certainly easy enough to try eh?

Might be your exhaust manifold starting to go though. I heard my driver's side one making some noise for the first time this morning. Experienced tech told me it was just starting to go a couple of months ago, and I heard it when he pointed it out from under the hood, but this is the first time I've heard it from inside the truck. Ho-hum...

Brent

Thanks! I'll check for the . Is the something I can see? What's the best way to check for this?

There's no good way to check short of pulling the heat shield off the top of the manifold and looking for soot on it where the crack is below it, but that's a bit of trouble. Otherwise just have a dealer check for you, an experienced tech will know the sound. Trouble is, if it only does it cold, you'll have to drop it off overnight, or in the morning on a really cold day.

Brent