Best 12-Volt Air Compressor for RVs, Cars, and Trucks in 2023

The Viair RV air compressor comes in two versions - the 400P-RV Automatic and the 450P-RV Automatic.

The difference between the two models comes down to two things - duty cycle (run time) and cubic feet per minute (CFM - how much air a compressor puts out in a minute).

Which one you need depends on how large of a tire you will be inflating.

Pick the largest sized tire you will be putting air into, and choose accordingly.

Viair recommends the 400P-RV Automatic for RV tire sizes up to 40 inches in diameter.

For tires larger than 40 inch diameter, they recommend the 450P-RV Automatic.

See the 'what size are my tires' feature in the guide to learn how to measure RV tire size.

To give you an idea of how large of an RV tire you need to exceed 40 inches, only the largest of the 22.5 inch diameter tires (those found on many medium to large Class A's) exceed 40 inches in diameter.

The 'smaller' 22.5 inch motorhome tires still come in under 40 inches in overall diameter.

While you definitely need to measure your tire size, you pretty much can't go wrong with the Viair 400P-RV 12v air compressor for most RVs.

Okay, now that we have Viair's recommendation out of the way, let's dive more into the difference between the 400P-RV Automatic and 450P-RV Automatic.

The 400P-RV Automatic has a lower duty cycle but puts out more air each minute (higher CFM rating).

The 450P-RV has a longer duty cycle (it is rated at 100% duty cycle which means it can run without a break) but doesn't put out as much air.

With 40+ inch tires, you want to go with the 450P-RV that has the 100% duty cycle.

Because, in theory, it will be running longer to inflate the larger tires.

Therefore, duty cycle might become an issue (especially if you have 6 or more tires on your rig).

So why not go with the 450P-RV Automatic, with the 100% duty cycle, for any sized RV tire?

You could, but then you are having to deal with waiting longer to inflate a tire.

Why?

Because the 450P-RV Automatic puts out less air volume per minute (which is one of the reasons it has the 100% duty cycle).

That's why the 400P-RV Automatic, with the higher CFM rating  is the more popular option.

It's more than enough except for the largest RV tires, while giving a faster inflation rate.

However, at the time of writing this review, the 450P-RV Automatic is less expensive.

So it's a trade-off, as are most things in life.

Slower tire inflation rate, but higher duty cycle and lower price = 450P-RV.

Quicker inflating speed with a lower duty cycle, but a higher price = 400P-RV.  

And yes, there is a very noticeable difference in the amount of time it takes these two compressors to fill the same sized RV tire (see RV air compressor fill rates above).

Now that we've covered the differences between the Viair 400P-RV Automatic and the Viair 450P-RV Automatic, let's cover what is the same.

Besides the actual air compressors themselves, everything else is the same.

The 400P-RV Automatic and 450P-RV Automatic air compressors both have a mostly metal body that is mounted to a sand tray. 

The compressor head has cooling fins, while the handle is foam wrapped to protect your hands. 

On the front of both compressors is a foam air filter inside a metal body.

This air filter is replaceable (spares included) and will keep dust from harming the compressor internal components.

You have to install this filter assembly before first use (do not use thread tape).

There is a 1/4" quick disconnect coupler fitting on the back side of the handle. This is where the air hose connects.

Both the 400P-RV Automatic and 450P-RV Automatic air compressors come with two 30' coiled hoses.

Each of the coil hose sections have quick disconnect couplers. You can use just one hose or both.

Though the hoses are 30' each, you would have to use a decent amount of pulling force to get them to a full 60'.

You would also have to make sure the compressor doesn't get pulled along.

No biggie as the two hoses will reach just about any possible tire configuration without needing to be stretched completely out.

Both of these compressors has a tire inflation 'gun'.

It has a trigger that allows you to stop and start the flow of air into the tire you are inflating.

On one end of the air inflation gun you attach the hose and on the other end you connect one of two included air chucks.

The air gun has a bleeder valve that allows you to 'bleed' off air when a tire is over inflated.

To deflate the tire, make sure the trigger isn't pulled (otherwise air will be going into the tire), look at the pressure gauge to determine how much air needs to be let out, and depress the bleeder valve 'button'. 

Let some air out, release the bleeder valve, read the gauge, and release more air if necessary.

To get an accurate reading of the tire inflation pressure, release the trigger so no air is going into the tire.

Then simply read the actual pressure on the gauge. The gauge has a ±3% accuracy and we've found it to not be completely accurate, but is easy to read.

You may wish to purchase a dedicated tire pressure gauge if you want to be more accurate.

As mentioned above, two air chucks come with both RV air compressor kits.

• 45º press-on style air chuck that is primarily used to reach the inside tire of a dual-wheel setup (dually).
• 90º twist-on style air chuck that you use for all other (non-dually) tires.

While it may seem like a hassle to have to twist on the air chuck for each tire, it's actually a very simple process.

There's a high quality 'screw' mechanism easily attached to the tire valve. Barely any air leaks while being installed or removed.

Also included are three miscellaneous inflation tips that screw into the 90º air chuck.

They include:

• One needle style tip that you would us to inflate a ball (football, basketball, etc)
• Two cone shaped tips that are used to inflate items you might blow up with your mouth (inflatable mattress, pool toys, etc).

Both the 400P-RV and the 450P-RV air compressors have 8-foot power cords that have a replaceable, automotive style inline fuse (40 amp for the 400P and 30 amp for the 450P).

The unit comes with heavy duty (rated at 40 amps) power clamps that connect directly to vehicle batteries.

Clamping a compressor to a battery may concern some people, but there is really nothing to worry about if you do it correctly.

Negative gets connected last, disconnected first - make sure compressor is off when doing this.

A nice nylon carrying case is included that perfectly houses all the included bits of the kit.

Viair 400P-RV Automatic RV Air Compressor

While the Viair 84P and 85P truck, SUV and car tire air compressors are great little units, they do have one catch: 

How they get their power.

They use the cigarette lighter style power adapters that you 'plug' into a 12-volt power port.

Pretty easy to use and convenient! With one gotcha.

These 12v air compressors are pretty powerful units and put out a good amount of air flow.

However, this means that the compressors pull a good amount of amps (power) while running and require a cigarette lighter socket that can handle this higher amperage draw.

While we opened the review with this warning, we feel it's REALLY important to point out the power requirements of these compressors, so here is the warning box again:

Assuming that your vehicle tire size is below 31 inches and you have a 12-volt outlet that can support at least 15 amps of power use, the Viair 84P or 85P compressors may be right for you. 

Let's learn more about them.

The compressor body is a combination of plastic and metal.

The piston head has metal cooling fins that dissipate the heat caused by the operation of the compressor.

The handle is plastic, so it won't heat up during use.

There are rubber feet mounted to the bottom of the 84P and 85P 12-volt tire inflators.

These work great on a solid surface (think asphalt) but they don't stop the compressor from 'digging in' to softer surfaces when being used.

This won't be an issue for most people buying either of these compressors.

Also included with both compressors are three miscellaneous inflation tip adapters.

They either clamp into the press-on style air chuck on the 84P or screw into the screw-on style air chuck on the 85P.

They include:

• One needle style tip that you would use to inflate a ball
• Two cone shaped tips that are used to inflate items you might otherwise blow up with your mouth (pool toys, air mattress, etc).

On either side of the compressor body (back side) is a place to store the inflation tips.

The power cord is only 10 feet long, which is the shortest of all Viair 12v small compressor models reviewed on this page.

That may be an issue if you've only got one 12-volt outlet in your vehicle that is capable of handling the power requirements of the 12-volt tire inflator.

Also, the permanently attached air hose is just 3 feet long, so this won't really help with the reach 'problem' that might occur depending on the location of a suitable power outlet.

The Viair 88P, which attaches directly to your vehicle's battery, has both a longer air hose and power cord, generally eliminating any potential reach issues.

There is an optional 6-foot air hose extension that you can purchase for the 85P (twist-on air chuck).

The Viair 84P and 85P 12-volt tire inflator has a built-in gauge that reads up to 100 PSI and is located on the back portion of the handle. This makes it easy to read the amount of air inside the tires.

While Viair doesn't publish accuracy specs for this tire gauge, we chatted online with them and they confirmed that it has a ± 3% accuracy.

You may wish to have a dedicated air pressure gauge on hand to check your car tire pressures quickly.

A vinyl storage bag is included with the 84P and 85P 12v tire inflators.

This 12-volt compressor attaches directly to your vehicle's battery.

It's best for vehicles that don't have a high enough amperage power outlet and cannot use the Viair 84P or 85P.

With a higher cubic foot per minute (air flow) rating than the Viair 84P and 85P, the Viair 88P gives even faster air inflation times for your car, truck or SUV tires.

Viair says that the 88P 12-volt tire inflator can be used on car tires up to 33 inches in diameter.

The vast majority of car tires, as well as most SUV and truck tires, fall within this tire size range.

To see if the Viair 88P 12v air compressor will work for your vehicle(s), determine your tire size by following these instructions in the guide.

Due to the power draw of the Viair 88P, it doesn't use a 12-volt outlet like the Viair 84P/85P reviewed on this page.

Instead it comes equipped with a 10-foot battery clamp power cord that connects directly to your vehicle's battery.

Clamping a compressor to a battery may concern some people, but there is really nothing to worry about when done correctly.

(Negative clamp connected last, disconnected first - make sure compressor is off when doing this.)

The 10-foot power cord, combined with the 16-foot air hose, means that you should have no problem reaching all your vehicle's tires.

At the end of the hose is a screw-on style air chuck, the only option for this model of Viair compressor.

Like all Viair compressors reviewed on this page, three miscellaneous inflation tip adapters are included.

They screw into the screw-on style air chuck on the 88P.

They include:

• One needle style tip that you would use to inflate a ball
• Two cone shaped tips that are used to inflate items you might blow up with your mouth (pool toys, air mattress, etc).

On either side of the compressor body (back side) is a place to store the inflation tips.

The Viair 88P comes with a storage bag that provides a bit of protection while not in use.

The Viair 400P Automatic and 450P Automatic are great portable off-roading air compressor options.

They are built to withstand harsher environments while offering a good air flow rate.

Also, you can move from tire to tire without having to turn off the compressor.

Viair is well known for making some of the best 12v air compressors (heavy duty) that withstand heavy use over time.

They also provide the ability to quickly inflate your aired down off-roader tires after a long day on the trail. 

Viair makes the gold standard when it comes to off-road air compressors.

Viair recommends the 450P Automatic truck tire compressor for 35 inch + tires because these larger truck tires require more air so the compressor will be running longer.

With longer run times, compressor duty cycle becomes an issue, so you generally want an air compressor that is able to handle the extended use (the 450P Automatic has a 100% duty cycle, which means it can be run non-stop).

So why not go with the 450P Automatic, with the 100% duty cycle, for any sized truck tire?

You could, but then you are having to deal with waiting longer for your tires to air up because the 450P Automatic puts out less air volume per minute (which is one of the reasons it has the 100% duty cycle).

Unless you are running with larger off road tires, the 400P Automatic may be a better choice. It is able to inflate tires quicker (it has a higher air compressor output, which results in a lower duty cycle) which means you spend less time airing up your off road tires.

See the off road air compressor fill rate tables to see how much of an inflation time difference there is between these two off-roading air compressors.

Now that we've discussed the differences between the 400P Automatic and the 450P Automatic air compressors, let's cover what is the same.

Besides the actual air compressors themselves, everything else is the same.

The 400P Automatic and 450P Automatic off-road air compressors both have a mostly metal body.

The compressor head has cooling fins, while the handle is foam wrapped so it doesn't get hot.

The compressor bodies are mounted to a diamond plated sand tray that is designed to keep the compressor from sinking into loose soil under use.

Without a sand tray, the vibration caused by a running compressor can cause it to sink into loose soil or sand. The sand tray offers a large surface air to help counteract this 'digging' tendency.

Both air compressor models have a foam air filter assembly that screws onto the front of the compressor body.

This foam filter is user replaceable (spares come with each kit) and helps keep dust from harming the air compressor internal parts.

Before you first use the compressor, you have to install (screw on without using thread tape) the assembly - a simple process.

A 30-foot coiled hose is included with both air compressor kits.

The hose connects (via a 1/4" quick disconnect coupler) to the back side of the compressor handle.

Because the hose is coiled, you have to be careful when extending it out the entire 30 feet.

You have to use a decent amount of pulling force on the air chuck end and have the air compressor itself anchored down (for example, have someone hold it) or else the compressor will be pulled along.

This is only an issue if you are fully extending the hose, which you won't do except in the most extreme circumstances.

Under 'normal' use, the coil hose presents no issues.

A tire inflation 'gun' comes with both the 400P and 450P Automatic.

The 'gun' has a trigger that allows you to stop and start the flow of air into the tire you are filling up.

You connect the air inflation gun to the air hose and then attach the press-on air chuck to the tire you wish to inflate.

The air gun has a bleeder valve that allows you to 'bleed' off air when a tire is overinflated.

To deflate the tire, make sure the trigger isn't pulled (otherwise air will be going into the tire), look at the pressure gauge to determine how much air needs to be let out, and depress the bleeder valve 'button'.

Let some air out, release the bleeder valve, check the reading of the gauge, and release more air if necessary.

Three miscellaneous inflation tip adapters are included, which clamp into the air chuck.

The tips include:

• One needle style tip that you would used to inflate a ball
• Two cone shaped tips that are used to inflate items you might blow up with your mouth.

Both the 400P Automatic and the 450P Automatic off-road air compressors have 8-foot power cords that use a replaceable, automotive style inline fuse (40-amp fuse for the 400P and 30-amp fuse for the 450P).

At the end of the power cord are heavy duty (rated at 40 amps) clamps that connect directly to your vehicle's battery.

Clamping an air compressor power cord to a battery may concern some people, but there is really nothing to worry about if you do it correctly.

(Negative connected last, disconnected first - make sure compressor is off when doing this).

Included is a nice nylon storage bag that houses all the included bits of the kit.