Sunday, July 10, 2011

Minimize the cost per mile driven

With fuel prices rising again, oil is back near $100 a barrel, you will probably want to minimize your cost of driving. Some helpful hints are common ones, but others are some lesser know things. One thing I have discovered in my years of working with cars and being around the car culture is that there are similarities between vehicles that get really good mileage and high performance vehicles.

1. Proper tire pressure
Keep your tires properly inflated. This will help decrease the rolling resistance (friction between your tires and the road) increasing fuel mileage. The higher tire pressure you have the lower rolling resistance between them and the road. While it may sound good to just crank the pressure way up this isn't a good thing either as it will affect the ride quality, tire wear, and safety.

2. Clean your car out
Not only will your friends want to ride in your car you can cut your fuel consumption. Granted in most cases this won't amount to much if any but if you carry around a bunch of junk (10's to hundreds of pounds) there might be a noticeable difference.

3. Keep your vehicle tuned
By keeping your vehicle properly maintained you can keep it running as efficiently as possible. See my previous posting on a vehicle maintenance schedule. Not only will this schedule keep your car running for a long time it will keep it running optimally.

4. Fuel saving tires
Fuel saving tires can help reduce your fuel consumption as they offer lower rolling resistance between your tires and the road.

5. Decrease drag
Remove external accessories for your vehicle. Just as cleaning out the junk can increase fuel economy so can removing unneeded exterior accessories. Typically this will be things like roof racks, bike racks, hitch accessories. Not only are you decreasing the weight of your vehicle, but you are decreasing the amount of drag caused by the wind hitting these things.

6. Use the correct gas
People seem to think that using premium gas will increase their fuel economy, the truth is if your vehicle is running correctly it won't. The truth is your vehicle was designed to run on gasoline with a specific octane (typically 87, 89, or 91). Granted using a higher octane won't hurt your car, but it does cost more money. By running a lower octane fuel in your car than recommended in you will waste fuel. This is because modern cars can compensate for too low of an octane by dumping more fuel in. This will prevent preignition, but will cause your car to run rich and will shorten the life of O2 sensors and catalytic converters. The truth is gasoline regardless of octane contains the same amount of energy.

7. Use synthetic fluids
Synthetic fluids can help increase your fuel economy. Granted they are more expensive, but they last longer. I cover synthetic oils in detail in this post. In my daily driver I run synthetic oil in the engine, synthetic transmission fluid in the transmission, and synthetic gear oil in the read differential. Most of the benefits of synthetic fluids come from the superior lubrication, decreased friction, and better flow, it takes less energy to move them around.

8. Use lighter oil
You can get better fuel economy by using a lighter oil. In my daily driver I run 0w30 in the cold Minnesota winter and then work up to 10w40 in the summer using either 5w30 or 10w30 in the spring and fall depending on temperature. As temperatures warm you shooed be using heavier oils to protect your engine, but don't use a heavier oil than necessary.

9. Gas coupons
Not all states allow or have gas coupons but I know here in Minnesota several gas station chains have gas coupons. Both Kwik Trip and Holiday station stores have gas coupons in the St. Paul paper for up to 7 cents off a gallon. The Kwik Trip coupons are in the St. Paul paper on the first Wednesday of the month, and the holiday coupons are in the St. Paul paper on the last Wednesday of the month. Additionally you can sometimes find gas coupons online for gas stations like Holiday Station stores have.

10. If your car takes 89 octane some stations sell it at the price of 87 octane
If you are unlucky like me to have a car that takes the mid grade (89 octane) you are kind of stuck paying a higher price per gallon for gas unless you know what gas stations sell the mid grade (89 octane) at the same price as regular (87 octane). This can save between 7 and 12 cents a gallon. I know that the Kwik Trip stores near me do this as do a number of the Holiday gas stations.

11. Use gas that doesn't have ethanol in it
In Minnesota this is basically impossible, yes you can buy non-oxy fuel but it is few and far between, but I believe that some states still sell gas without ethanol. If you are in a state that has a 10% ethanol mandate you loose about 3-4% of your mileage because of the lower energy content of ethanol.

12. Leave some distance between you and the one in front of you
Now it is theoretically possible to get better mileage by following closely behind another one. This is because of decreased drag, but is also dangerous and rarely produces good results. The reason for this is that you are varying your speed more than you normally would. By leaving more space between you and the vehicle in front of you 12. Leave some distance between you and the one in front of you you may not have to overcome more wind resistance, but you will be able to drive at a more constant speed. Also in rush hour traffic you can gradually slow down and speed up when doing this. Quick starts and stops really wreck mileage.

For the most part I practice what I preach and doing these things can lead to significant gains in mileage. My daily driver is an 1997 BMW 540i with a 5 speed automatic transmission, sport package, and has 215,XXX miles on it. This vehicle was claimed by the government to get 18 MPG combined and qualified as a cash for clunkers vehicle, I have never gotten that poor of gas mileage. My rolling average over the last 114,000 miles or so (I got the vehicle with 101,000 miles on it) has been 22.7 MPG according to the on board computer. This is more or less what I see when I fill up but is definitely in the correct range. I drive 32 miles one way (64 round trip) to work each day in rush hour traffic plus all the other little BS trips I make in a week. The best mileage I have ever gotten has been on long trips that are mostly open road. Typically on trips these I get in the 27 to 29 MPG range and have gotten that several times, most recently was last weekend going up to the iron range and back averaging 28.2 MPG round trip on a trip that was just a little over 400 miles. I could probably get better mileage but I do like to drive in a rather um "spirited" fashion especially on freeway entrance and exit ramps.

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