leaving car in Mexico

It is no longer possible to keep a foreign plated vehicle in Mexico once you start the process of temporary residency. You are correct in that it was legal in the past before they eliminated the FM3.

I think that with a Temporal you can have a foreign plated car. It is the Permanente that causes problems. A temporal is more like a one year FMM. But after so many renewals you either have to go to a Permanente or start the Temporal all over again. Like many we dropped our FM3 when all the changes began and just use a FMM.

Insurance is another potential problem.

The one time we had to make a claim with our carrier, we had to show proof that we had a temporary visa because we were insured as a tourist. Fortunately at that time we were not residents.

Your vehicles may not be insurable once you have your temporary residency because the policies most people buy are written for tourists.

As residents, insurance is readily available and is also valid in the US, probably Canada. Just have to have the correct policy.

That is definitely something you need to check.

All the airlines care about is collecting a form from everyone getting on the plane. They don't care if it shows a vehicle.

Once you have either your residente temporal or permanente card, you have to stop at the little immigration office in whatever airport, and they will have you sign a ledger and issue you part of a visa just to satisfy the airline.

Remember, when you fly back to Mexico, you can via e mail, provide a picture of your residente card and simply ask for a refund of the approximately $27US visa fee that is included in your plane ticket. Very easy to do.

Legally, once you register your residente temporal (congratulations!) you aren't allowed to have a vehicle on a TIP in country. Will you get caught? Very very probably not. IF you were, you could have your vehicle impounded. The same goes for the RV on the 10 year permit.

I will admit that we drove our RV down and back one time after we had our residente permanente, knowing the potential problems, and did fine.

Good Luck!