2007 LS, 2.2L, auto, 286,123 miles. Note all of the numbers that I give are from the onboard dash display, I have not verified these numbers by other methods. Ok here goes. Before the timing chain started going bad most likely due to my error of not keeping up with making sure that the car had enough oil. I was getting high 23’s low 24’s mpg and water temps between 172 and 210 high. The mileage dropped off to 21’s and 22’s and the temps went between 178 and 220. My fan does run. Now after doing the timing and balance shaft chains and water pump the mileage crept back up to 24.1 but then quickly dropped back into the low 22s mid 21s. Temps are between 175 low and 222 high. I do know that I have blow by and I am not sure if it is just valve guides or rings yet. I did borrow a compression tester so hopefully tomorrow I can check that. I am getting oil through the pcv system and am planning to put in an oil catching system in the very near future also. Question about that item quick. Someone suggested using an oil/water separator for air lines. Can that be installed laying on it’s side? Also, the car has picked up a “miss”. I have sprayed out the throttle body real good with cleaner and put marvel mystery oil in the oil to help clean things. It also seems like it’s losing power. It seems like the catalyst is getting clogged up but I don’t know. Interesting thing is that through all of this the CEL only illuminates in the bulb test mode and no codes are in the system so I am totally confused. 1 last thing. With the engine/transmission combination I have does anyone have any inkling on what rpm I should be turning at 55mph assuming I am running stock tires/wheels? Thank you to all who can give me some advice and suggestions.

 

Here's one interesting piece
I was having a sometime P0101. Even when the code was in pending status, I would get a driveability issue, namely, the turbo would shut down. CEL would not be lit at that point. Then after 15-20 miles, the turbo would come back, but not usually in 1st gear(manual transmission) and often not even second. Shift to 3rd gear, boost back! Code still pending.

Moral of the story, even pending codes, CEL not lit, can cause issues. It's good to have a code reader in the car, check for pending codes.

 

I finally found my code reader and indeed there is a pending 0300 code. Any ideas what might be causing this? I do know from the reader that it says multiple/random cylinder misfire. Everything I can think of would’ve caused the CEL to make its presence known. Thank you so very much for your guidance this far.

 

A P0300 can be many things including a burnt exhaust valve, wrong spark plugs, bad coil

https://www.obd-codes.com/p0300

 

P0300 means "unidentified misfire detected" not whatever nonsense the reader "says". It won't light the CEL until the catalytic converter is in danger.
If you have air brakes you might want a oil/water separator, more Farcebook nonsense.
Coolant temp should never get below 180F, bad t-stat. Fan does not turn on until 219F then off when the temp gets to 180F.
Blow by is from rings. Lots of blue smoke from valve guides.
Any oddities with oil or water levels? Check the water under the pressure cap, not just the bottle.