I have an '04 F150 with around 165K on the clock. Bought her going on 3 years ago in 2010 with 117K. Running great til now, hell she still runs great, plenty of power, no weird noises other than a brief rattle on startup.

Today I noticed a nasty blue oil puff on startup. I saw it once before but it was nasty and rainy outside so I attributed it to the condensation in the exhaust.

I checked the oil and it was about a quart low after 4000 miles. So I dropped a new quart in.

Checked the antifreeze, I haven't changed it in a year or so, so it's pretty ugly looking. I'm thinking about replacing the antifreeze and checking to see the color in a week or so.

I've always had a bit of a rattle on startup on this thing, I keep Motorcraft oil filter on it, and I run Platinum Pennzoil 5w20 in it. No other weird noises other than the usual Triton noises, nothing damaging sounding. I'm thinking valve guides/seals?

Am I looking at a full on engine replacement/rebuild soon?

 

A puff of smoke on startup is probably a valve seal leaking a little oil into the cylinder when the engine is sitting. A quart of oil in 4k miles is not unusual. I don't think either one is serious, just normal for an engine with 165,000 miles on it. I wouldn't be thinking about replacement or rebuild yet.

 

I have suddenly noticed a larger amount of oil usage in the past few months.
Normally I'd get about a half quarter in a 5K oil change.
And while the motor runs fine, it does seem to have less power. I've heard of bad catalytics causing excessive oil usage, is it possible my oil usage is connected to bad catalytics and I have compounding minor problems?

And finally -- how bad are valve seals to replace?