In the last 12 weeks I've went from 24.6 MPG to 17.1, I know weather is one issue but WTF I've got new tires, air filter, oil (correct viscosity) regularly use fuel additives amsoil, this is blowing my mind because this is the field I'm used to troubleshooting and nothing is working. I've taken it in to the Honda dealership and they are retards literally I knew more than the (Tech) that performed the audit.
Any suggestions?

 

You said this is the field you are used to troubleshooting. I would be looking to you for help.
For me, the question would be two fold, is it the engine that is the cause or is it something else
Engine would be air filter, oil, Evap, EGR, spark plugs, etc
Take a look at the accessory belt
Is the AC clutch stuck on?
Is one of the pullies hard to turn??

Something else would be tires, brake calipers, etc
I would be looking at the wheels to see if they are bent out of shape.
Are the new tires properly filled up. Poor pressure and instantly poor fuel mileage
Then there is the chance that the brake calipers are stuck
Raise the wheel in the air and spin it.
Then step on the brake and then spin it again
Is it stuck??

But, I am not good at this troubleshooting
So tell me what to do.
I am getting poor gas mileage in the winter too.

 

LOL,
Okay your good, I did the following things you'd stated but failed to list them due to my boss's and senior advisors mindsets LOL I usually list every single thing thus boring the hell out of anyone and then I find you. LMFAO yeah I'm 50+ and have to explain to usually a bunch of retards why their repair is costing hundreds of thousands because their system in place was neglected in response to the management overriding a system set to not fail. 😁

 

Possible winter driving conditions consume for fuel than in warmer weather conditions. milage can be 12% lower at 20 degrees than in warmer climate.77 degrees. and on short trips 3-4 miles can drop to 22% lower. found on Q and A in Google search.