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A Tale of Two Engines: V6 Versus V8

Most police vehicles are available with a base V6 engine and a more powerful optional engine, either a twin-turbo V6 or a big V8. The choice between standard and optional engines is the biggest alternate fuel decision a fleet manager will make.

The turbocharged Ford 3.5L EcoBoost V6 is an incredible engine, but has a low take-rate with the PI Sedan and popular PI Utility. The Charger is the most popular police sedan and the take-rate is split between the standard 3.6L Pentastar V6 and the 5.7L Hemi V8. Depending on gas prices, the take-rate varies from 50-50 to 30-70 in favor of the V8.

In making a decision between a standard V6 and an optional, more powerful engine, you must know the real differences in fuel use during actual patrol. The EPA City, Highway and Combined estimates are almost useless for predicting gas mileage during police use. For example, it is common for police admin vehicles to get the EPA City rating, but patrol vehicles may only get 70 percent of the EPA City rating. Consider these figures from the New Hampshire State Police and the Lake County, Ind. Sheriff.



EPA City




EPA Combined





3.6L V6          

18 mpg

27 mpg

21 mpg


17.9 mpg


12.7 mpg

5.7L V8          

15 mpg

25 mpg


18 mpg


15.1 mpg


11.3 mpg


The EPA estimates may not apply enough to make a sound decision between two different engines. The EPA estimates may point to a difference in fuel use where, in fact, there is no difference whatsoever in police patrol use.


Myth of Cylinder Deactivation

Equally misleading for police use is the cylinder deactivation feature found on many V8 engines. While it varies manufacturer to manufacturer, cylinder deactivation only takes place at light throttle and at steady throttle. Think for yourself how often your police vehicles are driven with either a light throttle or a steady throttle. Never. That is how often cylinder deactivation is being used.

Cylinder deactivation is virtually useless in law enforcement. An engine with an EPA City rating of 15 mpg actually gets 11.3 mpg in patrol. That is a good indication that the cylinder deactivation is rarely if ever engaged. On the other hand, it is engaged at times during the EPA Highway lab tests, which partially explains a 25 mpg estimate.

While engagement or non-engagement while driving is arguable, there is a slam-dunk argument against any hope for cylinder deactivation helping the police engine. Cylinder deactivation does not engage during idle, either at idle in Park or at idle in Drive. At idle, all cylinders are operating. At idle, a larger engine uses more fuel than a smaller engine. More on this later.


Maintenance and Repair

The comparison of ownership costs between a V6-powered vehicle and a V8-powered vehicle can help justify the decision of which ‘alternative fuel’ to choose. Ownership costs, not counting depreciation, are typically divided into two categories: 1) operating costs and 2) maintenance and repair costs. Operating costs generally mean gasoline. Maintenance and repair include everything else like tires, brakes, oil changes.

Different engines may have different amounts of maintenance and repair costs. That said, these terms are frequently confused. Maintenance is scheduled, preventative care. It is all planned, predictable and expected. Repair is unscheduled, and perhaps sudden and nasty surprises. Repairs can be guessed at but not predicted. Maintenance involves an expense but repairs can be very expensive, starting with a tow in the middle of the shift.

Preventative maintenance is the same for most police engines today. Oil change intervals are all extended past 5,000 miles. The antifreeze is all good for 100,000 miles. The transmission fluid change interval from the same manufacturer is the same. Specific to FCA engines, the older 5.7L Hemi V8 required new spark plugs every 30,000 miles—but no police department followed that maintenance schedule. Today, the Charger’s 3.6L V6 and 5.7L V8 both use 100,000 mile plugs.

Repairs are different. The problem when comparing repairs between V6 and V8 vehicles is that many repairs are not fully documented as to the cause, and most repairs are due to something other than the engine. With the Charger Pursuit, the front A-arms immediately come to mind. Of course, the front suspension (including the brakes) has nothing to do with whether the sedan has a V6 or a V8.


Latest Technology Engines

In comparing the V6 to the V8 in the Charger, it is important to gather data only from the latest engines. Engine technology changes all the time. The addition of variable valve timing or direct injection all effect fuel use.

Dodge made a huge change to the 5.7L Hemi V8 for 2009. They upgraded to the “Eagle” version, which has Variable Valve Timing. This boosted horsepower, but especially torque, so much that the rear gear ratio was dropped from 2.82 to 2.65 with no change in performance.

The 2.65 axle, however, improved fuel economy. The 5.7L ‘Eagle’ Hemi V8 used since 2009 is very different from the older 5.7L Hemi V8. Ignore any fuel or maintenance data from the pre-2009 V8-powered Chargers.

Likewise, Dodge dropped the very old technology 3.5L V6 after 2010 and introduced the 3.6L Pentastar V6 in 2011. The 3.6L V6 used since 2011 is a totally different engine than the old 3.5L V6. The ‘Ward’s Ten Best Engines’ 3.6L Pentastar V6 is superior to their 3.5L SOHC V6 in dozens of ways. Ignore any fuel or maintenance data from the pre-2011 V6-powered Chargers.


New Hampshire State Police

The New Hampshire State Police have been running Charger Pursuits since 2006. They have extremely detailed ownership data on almost 150 Chargers for every model year since then. Their excellent fleet documentation includes the make, model and year, of course. However, it also includes V6 or V8, starting and ending odometer readings by quarter, and fuel use by vehicle for every quarter.

From this, their spreadsheet calculates total miles driven, total fuel use, average miles per gallon, and annual fuel costs. For maintenance, they track total routine maintenance costs and total unexpected repair costs per vehicle. With all this data, it is easy to calculate total operating costs and total cost per mile.

The vast majority of their Chargers have the 5.7L V8; however, they have 11 2012 to 2014 Chargers with the 3.6L V6. We took the data from those 11 2011 and newer V6-powered Chargers and exactly matched them to 11 2009 and newer V8-powered Chargers. That is, we pulled data from 11 V8-powered Chargers that had virtually the same odometer readings and the same miles driven that year.

A new 2014 V6 Charger with 9,600 miles on the odometer was compared to a new 2014 V8 Charger also with 9,600 miles on the odometer. A 2012 V6 Charger with 65K miles on the odometer that logged 37K miles the previous year was matched to a 2010 V8 Charger with 67K miles on the odometer and 48K miles put on the same year.

There was a wide variety in the vehicles sampled. The V6-powered Chargers had ending odometer readings as low as 10K miles and as high as 72K miles. The V8-powered Chargers had ending odometer readings as low as 10K miles and as high as 74K miles. The miles logged that year ranged from 10K miles to 37K miles for the V6 cars and 10K miles to 48K miles for the V8 cars.

There was an equally wide range of fuel economy readings for each engine. Some of the V6 Chargers averaged 14 mpg, while some got 21 mpg. Some of the V8 Chargers averaged 13 mpg while some got 20 mpg. The maintenance and repair costs also varied widely by engine. The combined costs for the 3.6L V6 ranged from zero dollars that year to $1,400, while the 5.7L V8 costs ranged from $8 to $2,200.

The 11 V6-powered Chargers had an average odometer reading of 39K miles and 21K miles logged that year. The 11 matching V8-powered Chargers had an average odometer reading of 40K miles and 21K miles put on that year. That is as apples to apples as it gets when trying to decide between powertrains.

Based on the NHSP experience, expect the routine maintenance costs to be identical between the 3.6L V6 and the 5.7L V8. With these 22 NHSP Chargers, the annual total maintenance cost was $405 (V6) and $408 (V8). You may also anticipate the unexpected repair costs to be identical between the V6 and V8 engines. The 11 V6 Chargers averaged $93 per year, while the 11 V8 Chargers averaged $49 per year. When maintenance and repair are combined, there is no real difference in this aspect of ownership costs between the V6 and V8.


The Big Difference

The increase in residual value of the vehicle will almost certainly offset the initial cost for the optional engine. In some cases, the increased residual has proven to be much more than the cost of the bigger engine. To keep it simple, assume these figures cancel one another. The maintenance and repair costs associated with the V6 and V8 engine are also the same. That leaves just one area where there is a clear cost of ownership difference between the V6 and V8: fuel use.

These 11 NHSP V6-powered Chargers averaged 17.87 mpg over a combined 229K miles. The matching 11 V8-powered Chargers averaged 15.14 mpg over a combined 226K miles. In NHSP use, the 3.6L V6 engine gets an average of 2.7 mpg better mileage than the 5.7L V8 engine. At 25K patrol miles per year, that is 250 gallons of gas per car.

As we go to print in January 2016, the national average price for unleaded regular is exactly $2.00 per gallon. In mid-2015, it was $2.80, while in mid-2014, it was $3.70. When gas is over $3.25 a gallon, the fuel expense becomes the largest piece of the total ownership cost. Not just the largest piece of total operating cost. Above $3.25, it costs more to fuel the vehicle over its service life than to own it. Gas was over $3.25 for most of 2014.

Based on the police average of 25K patrol miles per year, 17.87 mpg for the V6 and 15.14 mpg for the V8, a realistic engine comparison can be made. (Of course, you can fill in whatever numbers you have for any of this calculation.) At $2 gas, the V8 uses $500 more in fuel than the V6. At $3, it is $750 a year. At $4, the difference between running a V6 and a V8 is $1,000 per year, per vehicle. At the critical $3.25 per gallon mark, it is an $820 difference. That is not the total fuel cost; instead, it is just the difference between running a V6 and a V8 using NHSP data.

For all practical purposes, this V6 to V8 comparison also applies to the Ford 3.7L V6 versus the 3.5L turbo V6 used in both the PI Sedan and PI Utility. When the twin turbo EcoBoost V6 is driven hard, which is all the time in police use, it has the same fuel use as a typical V8. Of course, the increased residual value is also the same as a typical V8.

A special thanks goes to New Hampshire State Police Captain Christopher Wagner and Equipment Supervisor Wendy Langlitz and also to Lake County, Ind. Sheriff’s Department Commander Matt Eaton and Police Garage Supervisor Bill Laviolette.


Wendy Parenti is the Marketing and Sales Manager at of Adamson Industries, the major emergency vehicles upfitter and aftermarket component supplier located in the Boston area. She may be reached at Lt. Ed Sanow is the editorial director of Police Fleet Manager magazine and may be reached at




Lake County, Ind. Sheriff: V6 Versus V8 in Urban Patrol

Cmdr. Matt Eaton, fleet administrator with the Lake County, Ind. Sheriff’s Department, and Bill Laviolette, the police garage supervisor, helped us tabulate the fuel and repair costs between the two Charger Pursuit drivetrains. Lake County, Ind. is a heavily urbanized suburb of Chicago that also includes some rural unincorporated areas.

The V6 Charger is typically used by patrol supervisors, but they patrol along with the road deputies and respond to assist across the entire county. The V8 Charger is typically used by patrol deputies. The tasks are more for calls for service and less for dedicated traffic enforcement.

Of the four Chargers in the data set, one of the V8 Chargers is driven by a very active K9 deputy, a supervisor who carries hundreds of pounds of cargo. The other V8 Charger is driven primarily by a drug interdiction deputy, a combination of cruising, brief periods of acceleration, and long periods of idling during stops and searches.

One of the V6 Chargers is driven primarily in unincorporated and rural areas. The other V6 Charger is driven primarily in urban and suburban areas, i.e., traffic lights and uneven traffic patterns. The two V6 cars are driven by field supervisors. While these are not driven as hard, nor carry as much cargo as the V8 cars, they are constantly driven cross-county to respond with and assist patrol units.

Laviolette has been with the police garage for 15 years, and has had experience with both generations of Charger Pursuit, the new ‘Eagle’ Hemi V8, and the older Hemi V8. Due to budget issues preventing the purchase of new vehicles, Lake County puts about 200,000 miles on their vehicles. 

With an average of 35,000 miles on the 2013 Chargers, they have experienced zero unexpected repairs on the 5.7L V8 drivetrain. With an average of 17,000 miles on the 2014 Chargers, they have experienced zero unexpected repairs on the 3.6L V6 drivetrain. The only maintenance of any kind has been routine oil changes every 5,000 miles. The brakes, which were a sore spot on the older Chargers, are lasting 18,000 miles. Pads and rotors are replaced at the same time. Lake County uses Raybestos Police Pursuit pads and rotors.

With a range from 12.45 mpg (urban) to 12.87 mpg (rural), the 3.6L V6 Chargers are averaging 12.66 mpg. With a range from 10.49 mpg (K9) to 12.06 mpg (interdiction), the 5.7L V6 Chargers are averaging 11.28 mpg. That is a difference of 1.4 mpg. “It is surprising to see that the two engines were so close in average fuel consumption. And surprising to see how low the actual numbers were,” Cmdr. Matt Eaton said.

The decision-making process may be that the mileage with all V6 and all V8 police sedans and SUVs is so bad that the engine size just doesn’t matter. Given the big difference in performance, there may be no practical difference in fuel economy between a V6 that gets 12.7 mpg and a V8 that gets 11.3 mpg.



Why Are the V6 and V8 So Close?

The patrol officers we spoke to were equally divided between the V6 is “enough” and the V8 is “required.” We did find one common thread: the launch from a stop with the 3.6L V6 is not strong enough. The 0 to 45 mph acceleration was a common complaint, while the higher speed performance from the 3.6L V6 was acceptable. This low-end performance gap was voiced more by urban departments than rural departments.

This low-end performance issue may explain why the 3.6L V6 engine doesn’t get all that much different gas mileage in patrol use than the 5.7L V8, especially in an urban patrol area. The 3.6L V6 sedan may be given more throttle and revved to higher engine speeds to get going, whereas the 5.7L V8 gives the acceleration needed with less throttle.

That said, the single most important aspect of patrol fuel economy may not be V6 versus V8. It may not be routine calls for service versus dedicated traffic enforcement. Instead, the single-most important factor in actual fuel economy in patrol use may be…idle time. With the fuel economy of exactly 0 mpg, idling wastes fuel. It also wears the engine and engine-driven accessories at a rate of 33 miles per idle hour.

A typical 3.5L or 3.6L V6 will use 1/3 to ½ gallon of gas per idle hour. In comparison, the 5.7L to 6.0L V8 will use ½ to ¾ gallon of gas per idle hour. The actual use depends on what accessories are putting load on the engine. The alternator charging the battery under a heavy amp draw is one such device. The A/C compressor is probably the heaviest engine load. Cylinder deactivation does not take place while idling in Park, Drive or Neutral.

You cannot manage what you do not measure. Every modern police package vehicle has an engine idle hour meter. Some also have engine operating hours, so be sure you understand what the driver information center is displaying. Engine idle hours are (generally) based on the time the engine is running and the transmission in either Park or Neutral. Engine operating hours are the total time the engine is running, both driving and idling.

The idle hours act as a tool to understand and manage idling. Like any such management tool, the data must be interpreted. Manage the engine idle hours by the patrol task, not the actual hours. For the anti-idle policy to have any credibility, look for wasteful, pointless idling. For example, the car idles for two hours while the officer is in the department writing a report. The car idles for two hours while the officer is at the range qualifying.

Published in Police Fleet Manager, Jan/Feb 2016

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