If they already know the identity of car and driver, receiving such "tips" on identity of car and driver would cost them no time whatsoever. Any incoming tip that "X might be the car" simply and quickly gets discarded, because they already know the answer. And such a choice would neither undermine MPD's integrity (as they said CLEARLY and REPEATEDLY right up front that they have "no reason whatsoever" to link this person to the crime), while also serving to get the SM busybodies out of their hair, leaving them chasing something that won't get in MPD's way or make them spend time.
Respectfully, I think you have a bias that has led you to minimize the Altima since back when all we had was one still pic.
IMHO, MPD looked upon the Altima with great suspicion. It would be against LE instincts to discount a car driving slowly around the perimeter of SWFA and flashing its lights, then sitting there for 4 minutes - not when a murder happened practically next door a couple of hours later. I doubt they would echo your belief that "it's probably just a mechanical malfunction". They would follow that lead like a dog chasing a bone.
The problem is, they couldn't read the plate or see inside the vehicle. If they couldn't get anything from SWFA's cameras, it's a safe bet that on that dark and rainy night in a rural area, no other camera would have given them anything.
So - they can't identify the vehicle or its driver. They don't have anything that ties the vehicle directly to a murder 1/4 mile away two hours later. Thus, they don't have probable cause.
And because they don't have probable cause, their best recourse is to put the info out there asking for help, but making it clear that the person is NOT a suspect - because probable cause is necessary in order to name someone a suspect. So they said what they had to say "no reason whatsoever" for CYA purposes.
I find it a bit shocking that you think MPD would have identified the car and driver and STILL put info out there as a distraction? It seems you take their words literally when it helps your point, but then you claim they are lying when THAT helps your point.
By the way, if MPD really wanted to feed us something to distract us, why not give us the entire SWFA video instead of just that still image back in May?
Edited to Add: you also seem to be expressing great confidence that MPD has "other video" - when there hasn't been one peep from them directly or in MSM that would lead us to think they have such evidence.