How to Get Better Gas Mileage on a V8

Since being patented in 1902, V8 engines have been a staple of sports cars, muscle cars and pickup trucks.  They provide awesome power and acceleration and are loved by drivers everywhere. At least until they pull in to their local filling station. 

V8s have certainly become more fuel efficient with many new engines getting up to 26 mpg on the highway.  Of course, with basic Hondas and Toyotas getting 40 to 50, that improvement doesn’t feel all that great.

Can you do better?  Certainly.  Here’s how to get better gas mileage on a V8.

How to Get Better Gas Mileage on a V8

We have identified 15 tips to help you improve fuel efficiency and 5 that you probably think will help but won’t!

Driving Tips

Don’t Speed

Driving at a little lower speed makes a huge difference, as in a 10% to 20+% improvement in mpg.  Consumer Reports took a Toyota Rav 4, Ford Fusion and Honda Accord and drove them steadily at 55 mph, 65 mph and 75 mph.

The savings were pretty stunning.  Going from 55 to 65 cost 4 to 8 miles per gallon.  Punching it up to 75 mph resulted in losing an ADDITIONAL 5 to 7 mpg.  That will add up over the course of a year.

I was basically able to replicate these results in a Jeep Grand Cherokee with a much larger engine:  30 mpg at 55 mph; 24 mpg at 65 mph; 19 mpg at 75 mph.

The moral of the story: leave a little early and don’t speed if you can help it.

No Hard Acceleration or Deceleration

This one is also a big deal and can be worth as much as 2-3 miles per gallon.  The reason is not surprising.  The harder you accelerate, the harder your engine works and the more fuel it consumes.  It’s simple chemistry and physics.

As far as decelerating goes, try gently coasting a few hundred yards or meters before coming to a stop.  During this time, your engine is idling while still covering ground and getting 3x – 4x its normal mpg.  Stopping quickly means you lose this benefit.

Smooth acceleration and deceleration have the added benefit of being better for your brakes, transmission and tires.

Plan Your Trip

There are several parts of daily commutes that are bad for gas mileage.  Examples include traffic jams, streets with a lot of stop lights, and roads with hills, just to name a few.  A related point is sequencing your stops to reduce total miles driven.

If you take a few minutes to plan your trip each day, you can avoid the worst of the obstacles.  It will also save you time and a lot of frustration.

Use Cruise Control

Cruise control helps remove some of the human foibles that hurt both fuel efficiency and safety.  For example, without cruise control the natural tendency is to match the speed of the car in front of you.  If that person is speeding, you tend to speed as well.

Another issue is distraction.  People tend to speed up or slow down when playing with the radio, retrieving something from the console, etc.  This results in taking your foot on and off the pedal which hurts mileage.

Don’t Let the Engine Idle Too Long When Stopped

Many cars these days have start-stop systems installed.  Basically, these systems cut fuel automatically when they sense a vehicle is at rest (e.g., at a stop light).  The logic is why burn gas while stopped?

Edmunds surveyed engineers who pegged the savings of such systems at 3% – 10%.  If you don’t have one of these systems, you won’t save that much fuel. However it does provide some idea of the mpg cost of running while idle.

While doing this at stop lights would be dangerous, consider turning off your engine when parked for a prolonged time (e.g., drive thru’s, waiting in a parking lot).

Reduce Weight

No, we’re not trying to get you to diet.  That said, it is easy to have weight accumulate in your car.  The more weight you have, the harder your engine works, and the more fuel efficiency drops.

It’s not unusual to have up to 200 pounds or more of unnecessary cargo in cars and even more in trucks.  Common culprits include golf clubs, kid’s toys, large bags of pet food, luggage…the list is endless.

Do a quick inventory.  This is one of the easiest savings to implement.

Draft Like You’re in NASCAR (legally of course)

We surveyed the internet and not surprisingly, there’s disagreement.  Some argue that you want to follow cars at a greater distance than the legally required minimum.  This prevents having to speed up and slow down in synch with the vehicle in front of you, which as we noted earlier, harms mpg.

Others argue that by following vehicles, especially trucks at a safe minimum distance, allows drivers to draft and save fuel.  Basically, the vehicle in front blocks the wind and reduces the resistance of the trailing car.

Our take is that you should always follow the law and drive within your comfort zone.  If on long freeway drives, you follow someone who is going a constant speed, then this may make a moderate difference.


Engine Tips

Optimize Your Engine Oil

First, change your oil as recommended by the manufacturer. If oil gets too dirty, the contaminants in the oil will increase friction, which increases strain and lowers fuel mileage.  It’s also very bad for your engine.

The second thing to consider is using synthetic oil.  I will say that this point is controversial. Motor oil companies claim that synthetics will save up to 10% or more in fuel costs.

However, a Canadian police force tested both types of oil in identical make and model cars with V8 engines.  After 60,000 miles, the cars with synthetic oils got 2% worse mileage.  Although this was a long-term study, which is good, it was not conduct to scientific standards.

Personally, I use Mobil 1 Synthetic and the best oil filter available in my cars.  I think it helps with performance and durability.  Any boost to fuel efficiency, if it happens, is just a bonus.

Clean Fuel Injectors

Fuel injectors spay vaporized gasoline into the engine.  A finer mist and more controlled spray improve efficiency.  Over time injectors will develop carbon deposits that can result in more coarse mist and less precise injection.  This will lower your mileage.

Having your injectors cleaned can cost $100 or more.  Unless you’re having engine problems, we suggest sticking to the maintenance schedule outlined in the owner’s manual.


Tire Tips

Keep Your Tires Properly Inflated

This tip is not controversial, and there is widespread agreement.  Underinflated tires get worse traction and make engines work harder.  They also significantly increase the risk of losing control of the car and of having tire blowouts.

The National Highway Traffic Safety Commission estimates drivers with properly inflated tires will see a 0.6% to 3% improvement in gas mileage.  That is 7 to 9 cents per gallon on the high end.

Keeping your tires properly inflated is a no brainer.  It is also easy to do at home.

Use the Right Tires

This one is a bit complicated.  There are several aspects of tires – tire size, tire weight, tread pattern – that may have opposing effects.

Tires with a larger circumference can improve mpg when traveling at highway speeds.  However, those tires may be heavier which hurts mileage.

Generally, for most cars the difference between one brand and another will likely not be all that great (we’re talking fuel efficiency, not handling).  Trucks with off-road tires may be a different story however.

Our view is that while there may be some fuel efficiency savings to be had, there are other factors to consider first when purchasing tires, like handling, safety and cost.


Other Tips

Use the Air Conditioner Sparingly

This gas saving tip is pretty much conventional wisdom.  It is also controversial.  Consumer reports argues that running the AC has a negligible impact on mileage.  Edmunds, in an older study, puts it at a negative 10% hit to mpg.

By my reading, the CR test was more rigorous and used more modern cars.  Our take is if you’re hot, use the AC.  Other tips we’ve discussed offer more proven upside with less pain. 

In short, don’t sweat it!

Be Careful with Roof Racks

Putting anything bulky on top of your car will seriously increase wind resistance and lower fuel economy.  Simply having rails with no cargo is not that big of a deal (~1% decrease in mpg). 

However, strapping down blocky suitcases or anything similar will have a big effect.  Edmunds, in the same test noted above, estimates up to a 21% percent reduction.  Carrying bicycles would have less resistance than something solid like luggage but would still reduce mpg.

If you’re going on a road trip and have a roof rack, you may have no choice but to use it.  However, make your cargo as low profile as possible and remove as soon as you can once you get to your destination.

Five Things that Don’t Matter!

Warming Up Your Car Before Driving

This has no impact on modern engines with fuel injection systems.  Even on cold days, 30 seconds to 1 minute is sufficient for oil to cover all moving parts in your engine.  If you’re like me, it takes 2 minutes to get my seatbelt on and find the right radio station.

If you have an older carbureted car, then a 5 minute warm up on cold days is advisable.  This is true not just for better MPG but also for overall engine health.  In older cars, gasoline doesn’t vaporize well in the cold.  Any that goes into the cylinder in liquid (vs vaporized) form, is being wasted to a large degree.

Replacing Dirty Air Filter

There seems to be no question that a dirty air filter will hurt acceleration, but what about fuel efficiency?  The Environmental Protection Agency actually shoots this one down.  This is another example of an old car versus new car phenomenon.

Dirty air filters restrict air intake.  That’s not really debatable. However, most newer cars have onboard computers that optimize the air-fuel ratio.  So, if air intake declines, the computer adjusts fuel flow accordingly.  MPG is not affected.

Using Gas from Branded Stations

Branding is a powerful thing.  Many people insist on brand name drugs at a 30%- 40% premium despite generics being chemically identical.  Not to mention the exasperated looks you get from your pharmacist.

Regarding MPG, many people feel they need to buy brand name gasoline (e.g., Exxon) versus filling up at their local Uncle Fred’s Quick Stop.  Many independent stations buy from big oil companies.  Often it is the exact same gas.  At worst, the gas may lack some fuel additives that have no real impact on miles per gallon.

Refueling in the Morning

In all honesty, I thought someone was pulling my leg here, but this notion is somewhat prevalent.  The hypothesis is that cooler gasoline is denser.  Denser gas in turn provides more fuel energy, better performance and better fuel efficiency.

The problem with this take is that gas is stored underground at all stations.  This keeps it at a reasonably constant temperature at all times.  So, don’t be late for work just to save some gas.  It’s probably not worth it.

Driving With Windows Down

This is another myth shot down by Consumer Reports.  The theory is that wind blowing in through the driver and passenger windows will increase resistance and make the engine work harder.

They tested a Honda Accord on a track at 65 miles per hour.  The difference between windows up and windows down was so small that it could not be measured.  If you like to drive with your windows down, you can do so guilt free.

How to Get Started

We have provided a lot of material, and it is easy to get overwhelmed.   Fortunately, a few of the tips are both easy to do and have a big impact on MPG:

  1. Don’t speed
  2. Practice steady acceleration and deceleration
  3. Inflate your tires properly
  4. Remove unnecessary excess weight (e.g., golf clubs from the trunk).

All these require are just a little practice and discipline. Seeing a 10% to 20% improvement is absolutely feasible.

Once you have these down pat, then you can tackle some of the more involved items on our list.


V8s are absolutely wonderful engines and a lot of fun to boot.  While they are known for being thirsty at the pump, getting better mpg is absolutely possible.

We have laid out several ways on how to get better gas mileage on a V8.  Don’t let this list overwhelm you.  Start with the easiest ones that provide the most bang for your buck.

A 20% or more improvement is absolutely achievable with a little bit of effort.

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