I assume you mean a regular start and not a remote start?
if things are staying lit up, disconnect both batteries, wait a minute or two and reconnect. I had a problem on my 2020 Wrangler where the radio, cluster, and shifter stayed lit up all the time but the Jeep ran. Battery disconnect fixed...
I think my JT and JL idle a bit rougher than the same Pentastar 3.6 I've had in several other vehicles, including JKs.
AT around 35k miles, the JL Wrangler developed a misfire and check engine light. Dealer had to replace one spark plug and coil for it.
You can change to the 7" unit with three things:
1) 7" radio
2) Faceplate for 7" radio
3) Anti-theft code for the new radio
If you do this, the only way to control volume will be with the buttons on the back of the steering wheel. The screen will always be on. It works fine this way as that's...
My Gladiator has shared garage space with a Grand Cherokee, then a JLU Wrangler, and now a Chrysler 300. I wanted something comfortable for long trips, was tired of SUVs like the Grand Cherokee, Explorer, or Durango, and a used 300 was pretty affordable.
My experience with the 2020 JT early in 2021:
Had to ask them multiple times to check. Nothing was on my receipt stating they checked it. I called "oh yes, we did. You are on the list". After 90 days still on the list. Jeep Cares got the parts to the dealer.
My experience with the 2020 JL later...
The solution is to install new TPMS sensors which will have new batteries. Years ago, I read an online how-to about someone cutting open a GM tire pressure sensor, removing the old battery , and installing new battery. It looked like a lot of work. Now maybe that particular sensor cost a lot...
The TPMS sensor stops sending a signal soon after the tire stops rotating to preserve battery life. So the spare tire would not send a signal even if it had a sensor.
I swapped on wheels from a Wrangler and in that application the spare does have a sensor so it would work if I installed it on...
I haven't seen this on my Gladiator, but the 3.6 in my 2012 Challenger and my 2015 JK did this occasionally. No real pattern I could establish and neither really used any oil. The smell was more of unburnt fuel than oil, though it sure seemed like gray smoke. I'd notice when I'd start the car...
The bad part is that for quite some time Jeep itself denied the problem. By the time people started experiencing this in Gladiator and being told "it's a Jeep thing", Wrangler JL owners had already been experiencing it for a year and a half.
It ended up being 3 years form JL introduction until...
The Dodge Hemi police cars don't use engine covers, haven't since they were introduced in 2006 or so (unless they've changed that recently). Therefore, I think the engine cover function is not performance related at all. I haven't seen under the hood of a new 3.6 squad to know if they ever used...
I've had a few other vehicles with the 3.6, including a Dodge Challenger, a Chrysler 300, and a couple Grand Cherokees, plus a long term Durango rental.
I always felt the 3.6 performed stronger in every one of those than in the Gladiator or Wrangler. It's acceptable, just not as satisfactory...
Wrangler JK had 16" wheels standard on the base Sport. With JL (and Gladiator) the base combination was now 17". This probably means 16" would even be unlikely without very specific wheels, let alone 15".