Technical Service Bulletins

Technical Service Bulletins are a great way to see what other are saying about your vehicle. Most TSB summaries can be accessed through the NHTSA, however, for more detailed information regarding your vehicle and the different external factors that affect how your vehicle performs, it is important to have accesses to complete TSB articles. These can range from fuel saving tips to tech tips regarding difficult DIY repairs. These bulletins are updated monthly and for one low yearly cost, you can have vehicle specific access to the information. Also included with these TSBs are recalls created since the initial sale of your particular vehicle on the market. View the article below for a complete TSB or click on one of the following links. ___________________________________________________________________

Ford F-150 Loose Brake Pedal TSB

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FUEL ECONOMY - CUSTOMER EXPECTATIONS

TECHNICAL SERVICE BULLETIN

Reference Number(s): 95-12-2, 97-6-8, 99-26-9, Date of Issue: March 17, 1997Superceded Bulletin(s): 95-12-2, Date of Issue: June 19, 1995

FUEL ECONOMY - CUSTOMER EXPECTATIONS VERSUS VEHICLE USAGEAPPLICATION

Model(s): Ford: 1988-93 Festiva1990-94 Tempo1990-97 Crown Victoria, Escort, Mustang, Probe, Taurus, Thunderbird1994-97 Aspire1995-98 ContourLincoln-Mercury: 1990-92 Mark VII1990-94 Topaz1990-97 Continental, Cougar, Grand Marquis, Sable, Town Car1991-94 Capri1991-97 Tracer1993-97 Mark VIII1995-98 MystiqueLight Truck: 1990-96 Bronco1990-97 Aerostar, Econoline, F Super Duty, F-150-350 Series, Ranger1991-97 Explorer1993-97 Villager1995-98 Windstar1997 Expedition, MountaineerBulletin No.: 97-6-8Date: March 17, 1997

NOTE: This bulletin supersedes Technical Service Bulletin 95-12-2 dated June 19, 1995.

ISSUE

Customers may perceive that vehicle fuel economy is lower than it should be, based upon EPA estimates. Fuel economy is most influenced by vehicle usage and duty cycle.

ACTION

Refer to the Fuel Economy brochure attached to this TSB issue. Consult this brochure and share with customers to improve their understanding of fuel economy factors.

WARRANTY INFORMATION

WARRANTY STATUS: Information Only.OASIS CODES: 622000, 690000

FUEL ECONOMY WRAP-UP

This material has been excerpted from Shop Tips and included here for your convenience. It should be shared with your customers.

HELPING THE CUSTOMER UNDERSTAND FUEL ECONOMY

It is important to distinguish between fuel economy due to the vehicle usage versus a malfunction. "Malfunctions" often are indicated when a significant reduction in fuel economy occurs when operating conditions remain the same.In this article, we pull together all the factors that affect fuel economy and see what they really mean for your customer and for you, the technician.

FUEL ECONOMY AND THE EPA NUMBERS

The basis for many customer fuel economy concerns are the EPA City and Highway mpg numbers on the retail sticker. These numbers are the result of test procedures that were originally developed to measure emissions, not fuel economy.Very few people will drive in a way that is identical to the EPA tests. You need to point out that the EPA numbers are for comparison between models at the time of purchase and do not reflect the fuel economy an individual will achieve in actual use. If a customer doesn't remember the EPA numbers on the retail sticker, he or she can get that information from the dealership.For your convenience in explaining these numbers to your customers, we have provided city and highway driving questionnaires. At the top of each questionnaire is a listing of the test conditions. This information is followed by a list of questions you can ask your customer (or customers can ask themselves). On the basis of the answers, it will become clear that if the customer's fuel economy is less than the EPA ratings, it is due to the driving cycle or the vehicle needing service.If a customer is driving in a manner very similar to the EPA test conditions and there has been a significant drop in fuel economy, there may be mechanical problems.

KEEPING TRACK OF FUEL ECONOMY

If you receive a fuel economy complaint from a customer, you need to determine how they arrived at their numbers.The odometer must be recording properly and they must be filling the tank with the vehicle loaded the same way and on the same level every time. If these conditions aren't met, it's hard to draw conclusions about anything but very big changes in fuel consumption.

DOES IT REALLY MATTER?

Below is a chart that shows fuel costs at various mpg's for a passenger car driven 12,000 miles, a heavy truck driven 12,000 miles and a heavy truck driven 100,000 miles. Two things are clear from these comparisons:1. The heavier the vehicle, the more the savings from improvements in fuel economy. 2. The lower the vehicle's average mpg, the higher the fuel cost.

For example:If the price of fuel is $1.00 per gallon and the vehicle is driven 12,000 miles:· Decreasing from 40 mpg to 37 mpg results in an increased cost of $24. · Decreasing from 20 mpg to 17 mpg results in an increased cost of $105. You can help your customer understand his/her cost factors by giving them this formula:

In words: Fuel cost equals miles driven divided by mpg and multiplied by the price of fuel.You may be able to use these comparisons to raise an important question if a customer complains about getting slightly lower fuel economy than expected: Does it really matter all that much? If the customer is driving an Escort for example, the answer might very well be, no. If the customer is operating a delivery truck, the answer could easily be, yes.

EPA CITY DRIVING CHECKLIST

EPA HIGHWAY DRIVING CHECKLIST

FACTORS AFFECTING FUEL ECONOMY

Fuel provides the power to move a load against forces that resist that movement. If a route were all downhill, you could coast, using no fuel at all. Real life is rarely that easy. A fuel efficient vehicle is one that has the horsepower to get the job done, while overcoming the resistances that stand in the way. Fuel economy can be looked at in two ways:1. Generating the power to move down the road. This involves three factors: 1. The horsepower the vehicle needs to overcome resistance. 2. The efficiency of the engine in generating the needed horsepower. 3. Horsepower to accelerate. 2. How the vehicle is operated. How the vehicle is operated is the owner/operator's responsibility. It plays a major role in fuel economy.

RESISTANCE AND HORSEPOWER

For a good understanding of the relationship between resistance and horsepower, the following equation for the horsepower (HP) needed for a particular speed is very helpful.

In words, this equation reads: The horsepower needed to achieve a particular speed equals the speed (V) times resistance (R) times the gross vehicle weight (GVW) plus the speed cubed (V3) times coefficient of drag (C) times frontal area (A). These results are divided by an efficiency factor.This equation is simpler than it looks. Let's go through it step-by-step:The two numbers, .01 and 375, are included in the formula to make the results come out as horsepower. They aren't directly necessary for an understanding of the basic formula.

MECHANICAL FACTORS

In the first part of the equation [V x .01 x R x GVW]:V is the speed the vehicle is operating at in mph.R is rolling resistance + grade resistance.Rolling resistance refers to the nature of the road surface. It takes more horsepower to maintain a given speed in soft sand than it does on dry pavement. It is interesting to compare rolling resistance to grade resistance. The chart below shows the effect of different surfaces as if they were hills to climb. For example: Driving on sandy dirt is like climbing a 3.75% grade.Grade resistance refers to hills. On a hill, it takes more horsepower to maintain a given speed than on level ground.GVW you are all familiar with. It's the Gross Vehicle Weight - the weight of the vehicle and everything in it.In this equation. V. R. GVW and the .01 are all multiplied together. This gives you the mechanical factors that determine how much horsepower you need to achieve the desired speed. If you double the speed, you double the effect of these mechanical factors.

ROLLING RESISTANCE AS GRADE

AERODYNAMIC FACTORS

Now we need to add in the aerodynamic resistance factors. They are represented by [V3 x C x A]."C" is an AIR RESISTANCE FACTOR! It is a combination of Cd and the density of the air. Air density varies somewhat with temperature and pressure. To compute the horsepower needed for speed in our equation, you should use the following value for C:C =.002 x Cd

NOTE: Air resistance isn't a significant factor below 25 mph. Cd is the coefficient of drag. It is a measure of the "sleekness" of the shape of an object and how well a fluid/gas flows over/around it.A stands for the frontal area. You might think that the greater the frontal area, the higher the overall resistance, but this isn't always true. Drag and frontal area have to be considered together. Vehicles A and C have about the same frontal area, but C has a lower drag coefficient, so the overall resistance is lower.V(3) is the desired speed cubed. This means V x V x V!V(3) x C x A tells us something very important. As speed increases aerodynamic resistance increases even faster! Let's see why that is. Looking at the speed (V) alone, let's compare V and V3 at 55 and 65 mph, and at 65 mph driving into a 15 mph headwind.55 (3) = 166,37565 (3) = 274,625. This is a 65% increase in resistance (from speed alone) as a result of only a 10 mph increase in speed (from 55 to 65 mph).Now let's add in the headwind. 65 mph plus a 15 mph headwind produces a speed of 80 mph through the air. 80 (3) = 512,000. With the headwind, the speed component of the aerodynamic resistance has increased an additional 86% over 65 mph with no headwind. Comparing an 80 mph air speed (65 mph + 15 mph headwind) to 55 mph, results in three times the resistance for a 25 mph increase in air speed.As you can see, the resistance due to speed alone goes up very rapidly. Added to this is the resistance due to aerodynamic drag and frontal area. To overcome all this resistance, more horsepower is needed, which, in turn, reduces the fuel economy. Anyway you look at it, higher speeds result in lower fuel economy.Going back to the formula, we see that all these factors we are talking about are divided by 375 x Efficiency. As we said before, 375 is a number that is included to make the answer come out in horsepower. What is Efficiency? In this case, it is a number (often around .85) that represents drivetrain efficiency. The amount of available horsepower from the engine is reduced somewhat as it passes through the drivetrain. Modern electronically controlled, lock-up automatic transmissions have increased the efficiency of the drivetrain, leaving more of the engine horsepower available to move the load.This equation can be applied to any operating condition. For example, it can be used to calculate the horsepower needed to move an off-road vehicle at 25 mph through soft sand. If this is an important objective in the design of the vehicle, the equation will indicate how much horsepower must be available from the engine under these conditions.

HORSEPOWER AND ACCELERATION

The equation we have just discussed is for a steady speed. Additional horsepower must be available for starting up and accelerating during operation. Sudden acceleration requires a lot of fuel and can greatly impact fuel economy.

AIR CONDITIONING

There are some misconceptions about the effect on fuel economy from operating a vehicle's air conditioner. At freeway speeds, it may be more economical to have the windows closed and the A/C running than to operate with the windows open. Open windows at high speeds produce significant drag which may reduce fuel economy more than running the air conditioning system with the windows closed.At low speeds, such as in city traffic, open windows don't significantly increase drag. Running the A/C under these conditions may affect fuel economy.

HOW THE VEHICLE IS OPERATED

PUTTING THE OWNER/OPERATOR IN THE PICTURE

Throughout this series we have focused primarily on engineering and design factors that have an impact on fuel economy. Government regulations and fuel availability concerns have driven these efforts. Your customers need to be aware that they also play a major role in achieving good fuel economy. Smooth operation goes a long way to maximizing fuel economy. This means driving at moderate (and appropriate) speeds, accelerating smoothly and avoiding sudden starts and stops.

VEHICLE SPEED

It should already be clear from the horsepower formula discussed earlier that high speeds result in poor fuel economy. Rapid acceleration is also a factor. Putting the pedal to the metal uses a lot of fuel. Studies show that operating a vehicle in a smooth, moderate way can save up to 10% on fuel consumption.

WEIGHT AND ACCESSORIES

It is clear from the horsepower formula that certain accessories and excessive weight will also reduce fuel economy significantly. Accessories include luggage racks and light bars that increase wind resistance. Trailers also contribute a lot of frontal area that results in increased wind resistance.Heavily loading a vehicle or towing a trailer will sharply reduce fuel economy. Doing both together just compounds the problem. If the customer is carrying or towing heavy loads all the time, he or she needs to understand that they cannot expect good fuel economy. If you are aware that the vehicle is being loaded beyond the design limits, you should point out that this is a potentially dangerous practice.

TIRES

Tires are a significant factor in fuel economy. Properly inflated, O.E.M. tires are part of the vehicle's overall design. Underinflated tires result in significantly lower fuel economy, as well as poor or potentially dangerous handling. Replacement tires that do not meet manufacturer's specifications can also result in lower fuel economy.

OIL

The right grade of high quality oil is, first of all, a critical part of good vehicle maintenance. The oil should be changed at least as often as manufacturer specifications call for. Certain oil grades contribute to fuel economy. In many vehicles, SAE 5W-30 oil improves fuel economy compared to higher viscosity oils. Follow manufacturer recommendations when it comes to changing oil. To assure the highest quality, select oil that displays the new API certification trademark.

CORRECTABLE VEHICLE-RELATED FACTORS

If a customer complains of sharply lower fuel economy, question him or her carefully. Make sure that their driving habits and the vehicle's loading have remained the same. Check for any new accessories that might be increasing resistance. If there are no apparent changes in operating conditions, you can look for service related concerns:· Check that tires are the right type and inflated properly. · Check the transmission or transaxle for slipping. · Routine maintenance such as new plugs or timing adjustment may be required. · Sensors or actuators may be malfunctioning. Look for diagnostic trouble codes. · Check for brake drag. · Check the thermostat. It may be closing, or it may have been replaced with an incorrect thermostat. Either way, if the engine doesn't come up to designed operating temperature, fuel economy will suffer. · Check that the emission control system is functioning properly. · In extreme cases, there may be base engine problems such as worn piston rings. · In very rare situations, the EEC may be functioning in "Limp Home" mode. This default setting allows the vehicle to be driven, but gas mileage will suffer.

THE TOTAL PICTURE

This series on fuel economy has allowed us to look at modern vehicle systems in a special way. Improving fuel economy involves almost every aspect of vehicle design from the shape of the body; to the design of the engine; to where the tires meet the road. Good fuel economy means that all these systems are working together properly. It also means that owner/operators are doing their part. Helping your customers achieve this desirable goal provides a valuable service.