What happens if I use a non-Honda brake fluid?

I have a newer Honda that is low on brake fluid. Manual says I need to use Genuine Honda fluid which is way more expensive and only recommends using a non-Honda fluid equivalent in an emergency situation, only if it's new and sealed.

So what could happen if I use a non-Honda fluid? Does it damage the system so I have to get it drained As soon as possible? Or is this just a scare tactic to sell more Honda products?

As long as you use the correct rating for your vehicle it is fine. The ratings are based on boiling point temps. Almost all manufacturers of products suggest their own products in order to boost revenues. It is nothing new!

You shouldn't ever need to add brake fluid because the level is supposed to go down as the brake pads wear and when the pads are replaced the fluid returns to the reservoir unless you have a brake fluid leak which is a serious problem that needs to be fixed as soon as possible. So you should never add fluid unless you are servicing the brakes and if so it it not necessary to use genuine fluid all that matters is that you use the correct type of fluid that it calls for such as DOT 4.

For brake fluid, it is the DOT number that is important, not the manufacturer. It should say on the cap or manual that you need DOT _ (usually 3, 4, or 5). As long as the bottle you buy has the matching DOT number, you're good.

I would highly recommend you only use genuine Honda Automatic Transmission Fluid but you can use any brand brake fluid as long as it meets the requirements of Honda. It will more than likely be Dot 3 but could be Dot 4. If you have to add fluid then you either have a leak or your brake pads are worn bad enough that they need replacing. As the pads wear the fluid level goes down. Once you replace the pads the fluid level will return to the full mark.

Look at the brake fluid reservoir cap. It likely says DOT 3 brake fluid. If it says DOT 4 or DOT 5 that is what you need. Any brand with the correct DOT rating number that matches the reservoir cap rating is fine to use. The brake fluid goes lower as the brake pads wear. You shouldn't need to fill it unless there's a leak in the hydraulic system. If the red brake warning light comes on and the parking brake is not on you likely need a brake job.

You ask what could happen? You will have a few more dollars in your back pocket

It is depending witch type of fluid you use
Dot 5

The bigger worry is why you are low on brake fluid.
The spec is what matters on the fluid.
Old fluid takes in water and this reduces it's boiling point and makes it dangerous in some situations
Brake fluid is very flammable