What are the risks of doing this?

Just how dangerous is this? A good way to get Interpol on your ass? Probably not, but you could have your weekend severely inconvenienced, end up spending a considerable sum of dough, be barred from Canada for life, and maybe tip off the FBI to other things you might be up to.

I don't want in any way to dissuade anyone from lying their way into Canada, I just want you to be armed with the facts.*

Canadian immigration law mandates procedures for U.S. citizens crossing in is as follows: Everyone at every border post will be met initially by a customs inspector. The initial customs inspector is authorized to
1) let you in,
2) interview you individually and/or search your vehicle then let you in, or
3) demand that you be held for further questioning by an immigration official at a hearing.
No reasons have to be given for any of these actions. The customs official cannot just demand that you leave without further hearing.

You are entitled to this hearing within 48 hours, and the said immigration official is authorized to
1) let you in,
2) interview you further individually and/or search your vehicle then let you in, or
3) demand that you be held for further questioning by a SENIOR immigration official.
You are entitled to your hearing with the Senior official within another 48 hours. The immigration offical cannot demand that you leave without further hearing.

The senior official can either
1) let you in,
2) interview you further individually and/or search your vehicle then let you in,
3) Deny you entry, or
4) hold you for trial and imprisonment/deportation for a felony criminal offense.
Since we have supposed in this node (see above) that no weapons, drugs, or illegal immigrants are involved, we are going to assume that nobody is in dander of facing #4. If you are, you are on your own. Merely lying to a customs or immigration official about the plans for your visit is NOT a felony in Canada.

And so, we see that the most you risk as far as time goes is as total of 96 hours in detention. Usually, they want to adjudicate things sooner, but then again, since they legally can be deeks about it and keep you there for the maximum, they just might.

At any point during detention you are free to give up your attemptt to enter Canada say you will turn around and leave if released. They may release you, but they don’t have to until after your meeting with the Senior immigration official. If you look like you might be doing some sort of serious felony, or that you might have some information to ‘share’ if enough pressure is applied, or if holding you for 96 hours will prevent you from engaging in whatever activity they think you will, they might just make you sweat it out for the full 96.

If the end result is that you don’t get in, whether you are explicitly denied entry or agree to give it up in exchange for release from detention, you can
1) be banned from Canada for eternity (unlikely but possible) or
2) for a set period of time (more likely), or
3) you will go on a ‘red flag’ list and will be under increased scrutiny at the Canadian border for the rest of your life (most likely).

Anyway, your car will have been kept safe the whole time and you will be free to leave. You cannot be denied entry back into the states (again, assuming no weapons or drugs), but operate under the assumptions that all ‘incidents’ (detentions) will be shared with American law enforcement. If you don’t want to start a file at the FBI, this is something to consider.

Something else to consider: What if you are in a group, and some of you get detained and some don’t? Or some get detained for a long time and some for a short time? That’s potentially up to 96 hours that you are separated and don’t know what’s happening to the rest of your group. They might keep you updated on the status of your friends - on the other hand, they might not. What if the driver, or the person with the keys is detained and the rest aren’t? What do the rest do? What if everyone but the driver is detained? As you can see, the possibility might arise that a hotel room or sleeping bags are needed. Contingency plans should be worked out for every situation. As far as I know, only the driver who entered customs is allowed to drive the car out. So if you’re not the driver and the driver is detained, only plan on getting as far as you can walk until he is released.

If you are making the crossing by bus or train, if detained the bus/train will not wait for you. You are responsible for securing your own transportation out of there upon release. They don’t let you ‘crash’ at the customs house and there are no refunds.

Now let’s talk about where you want to try your crossing:

Many posts are on secondary roads in rural places and are so small that the customs inspector is the only staff. Others, such as those along major highways in unpopulated areas, may have several staffers, including an immigration official in addition to the customs officers. The largest crossings (Detroit/Windsor, Buffalo/Fort Erie, Port Huron/Sarnia, and Seattle/Vancouver) have a staff of hundreds. At a one man post, you have the advantage that it is a pain in the ass for him to hold you there and wait for an immigration official, so he might be more pressed to let you through. On the other hand, he might not have anything better to do than watch you squirm. At large crossings, immigration officials are present in spades, so your wait might be less, but then again that just makes it all the more likely that your suspicious ass might be held for questioning. On the other hand, they might be too busy trying to intercept real smugglers and murderers to care about you. There are a lot of variables.

One more variable with a small crossing is that there is a small possibility that if you make it to the stage where you face a senior immigration official, this meeting might take place at a distant location, such as in a major city. As far as I’m aware, they will provide you transportation back to your crossing point upon release.

All of this sounds daunting and is a lot to consider, and we should always plan for the worst, but we shouldn’t lose site of the fact that it is damn easy to get into Canada.

Just remember:
Look like you’re not a threat
Give every indication that you are going to spend money
Give every indication that you have money to spend
Have an air tight story that everyone is well versed in
Have a reasonable explanation for everything suspicious

And, perhaps most importantly:
You haven’t actually lied until your vacation is over and you didn’t actually do what you said you would.

* It should have been stated, and cannot be emphasized enough, that the whole discussion in this node applies only to American citizens crossing into Canada overland from the U.S. Citizens of other nations crossing to Canada from the U.S., or Americans coming in from a third country, or foreign nationals going directly to Canada face much more intense scrutiny, and possible stiff life altering penalties. On the other hand, citizens of the U.S. flying or taking cruise ships to Canada face almost no scrutiny.