Is Revving your Car Bad?

Are you trying to warm up your car faster in the winter? We take a look at the myth that revving your car’s engine warms it up faster.

Many ages ago when cars with carburetors were in every driveway there was a practice of “warming up” the car before the morning winter commute. While ice and snow on the car will definitely slow down the morning departure, does warming up or revving the car’s engine help?

By Maurice Rodriguez
March 12, 2022

There are a few reasons why someone would want to rev their engine or idle it for prolonged periods. Some want to warm up their car faster and get some heat. Some are charging a dead battery that was just jumped. Then others are revving their engines for sport, challenging fellow drivers, or impressing a young lady.

We consulted the EPA to get advice on the pros and cons of revving your car or idling for prolonged periods. We will finally test this long-standing myth and put it to rest.

How revving your car’s engine to charge your battery? We find out that there may be some truth to this one.

Finally, we address how legal or illegal it may be in your state to rev your engine which can be considered an “exhibition of speed” in some states.

What is Revving your engine?

What exactly is going on when you rev your engine? Revving your engine is defined as pressing the accelerator when the car is in park or neutral.

The mere act of revving your car’s engine speed while it’s in park or neutral does not harm your engine, as long as you don’t do it for a prolonged period (more than a few minutes), and you don’t go past the red line, which means go into the RPM (revolutions per minute) red zone on your tachometer. If you want to rev your engine safely only got 2K to 3K rpm.

Revving your car’s engine passed the red zone will cause damage to your engine’s internal components like piston rings, rods, and may lead to your engine catastrophically failing. Like the gif below.

Is revving your engine in park bad?

Revving your car’s engine in park or neutral is an acceptable practice. But, it can cause damage to your car’s engine and waste unnecessary gas.

But, is it necessary anymore with modern fuel-injected cars?

According to the EPA’s “Your Car or Truck and the Environment”, “Revving the engine…can increase engine wear…overheat your catalytic converter, making it less effective and possibly damaging it.” Excessive revving (going passed the redline) for prolonged periods WILL cause excessive wear and tear on your engine.

Revving your car’s engine to warm it up faster in the morning is NOT recommended by most manufacturers. This is because most cars are designed to warm up as the car is being driven.

For example, your transmission fluid will only warm up when it’s engaged and running. Idling in your driveway will not circulate the transmission fluid until you start driving.

Another downside to revving your car’s engine is you are wasting gas while idling. “Long idles, and limiting car warm-ups in winter” are also not recommended by the EPA in the same article. The myth of revving your engine comes from the era of carbureted engines and since all modern cars use fuel injection, “warming up” your car is not necessary. Sorry. Myth busted.

What happens when you rev your engine?

Take a typical internal combustion engine the four-stroke engine. This engine has four distinct phases: an intake, compression, combustion, and exhaust. It is a four-cycle engine and when you rev your car’s engine, you increase the speed at which the combustion process is performed inside the engine block.

When you rev your engine, one complete four-cycle is a revolution of the crankshaft. This is why we measure revolutions in your tachometer. So that we know how fast the engine is spinning and know how hard we are pushing the engine. Push the engine too hard and you could cause engine damage. That is why engine limiters are placed on engines to avoid catastrophic damage. 

Does revving the engine charge the battery?

Yes, revving your car’s engine to 2k to 3k rpm will charge your battery faster. The reason revving charges your battery faster is that you are essentially increasing the engine speed that turns the belt that powers your alternator, which in turn charges your battery. This shouldn’t be done for prolonged periods of more than 10 minutes. Driving the car will help charge the battery just as efficiently.

Is revving your engine illegal?

Depends on where you live. Many different jurisdictions (cities, counties, and states) have very different laws regarding this practice. You should consult your local laws to know for sure if you are breaking any noise, or “exhibition of speed” laws.

We did some research in the top states for searches in Google for “Is revving your engine illegal? We found that many people are looking for some legal guidance on revving their car’s engine from Michigan to California. For legal advice, please consult an actual lawyer.

In California; Yes, it is illegal to rev your car’s engine. Under section 23109(c), “A person shall not engage in a motor vehicle exhibition of speed on a highway.” Revving your engine falls under the “exhibition of speed” and can incur a fine of $500 and up to 90 days in jail.

In Texas: Yes, it is illegal to rev your car’s engine. Under section 545.420.5, “A person may not participate in any manner in an exhibition of vehicle speed or acceleration.” Revving your engine falls under the “exhibition of speed” in Texas too. The penalty in Texas for revving your engine is a Class B misdemeanor, which can include 180 days in jail and a $2,000 fine.

In Michigan: Yes, it is illegal to rev your car’s engine. Under section 257.707c, “A motor vehicle must not… exceed…the following limits at a distance of 50 feet… (iii) Eighty-eight (decibels) DBA under stationary run-up test.” In Michigan, you will receive a fine of no more than $100 for violating Michigan vehicle code 257.707c. regarding noise infractions.

In Arizona: Yes, it is illegal to rev your car’s engine. Under section 28-708A, “A person shall not drive a vehicle or participate in any… exhibition of speed or acceleration.” The penalty for violating this code on the first offense is a fine of at least $250.

To get actual legal advice from a lawyer in Arizona check out this video made by the R&R Law group that does a really good job explaining this law more in-depth.

In Ohio: No, it is not illegal to rev your car’s engine. At least we couldn’t find any laws regarding engine revving or exhibition of speed. But, it may be illegal to idle your car’s engine while unattended if you are trying to warm up your car. This is an anti-idling law to stop stolen cars and exhaust emissions.

However, street racing is VERY illegal in Ohio. If you are revving your engine with the intention of racing, you could get your license suspended as a result of racing another driver.

All Other State Speed Laws

For a “Summary of State Speed Laws” in your state from the National Transportation Institute, you can click on the link and you can check out the laws, fines, and imprisonment terms in your state.

_{***DISCLAIMER: We are not legal experts or lawyers and this is not legal advice. We are only quoting the legal statutes found on the internet and do not take any legal responsibility if you break any city, county, or state law***}

Conclusion

Drivers rev their engines for lots of reasons but we have learned that for the most part revving your engine is an unnecessary practice. Nevertheless, is it a cool practice? Does the sound of high revving Italian engine get you excited? A resounding YES.

We are all things cars.