Wednesday, September 19, 2012

Diesel vs Gas

Earlier this year I wrecked my old car, a 1993 Nissan Altima.  It was a real beater, but I thought I was going to drive her for a while yet.  Now being the super cheap guy that I am it took me a long time to buy something else.  Purchasing a car is a big decision.  It will be with you for at least 5 years.  I had my Altima for 6 years, but it had been in the family since '93.  Over the span of 6 years some small expenses really added up.  Namely the purchase of gasoline.  Back then I was not too concerned about the way that I drove my car and did not think about the effects of my driving on my MPG and my wallet.  I usually got somewhere between 28-38 MPG.

Going in to purchase this next car I had really become conscious of how this added up over time.  I did my research this time.  The car's price and fuel efficiency were my priorities. I had two demands for this car.  It had to be right around $10,000 so I could pay cash for it and it had to get at least 40 MPG on the highway.  I do a lot of highway driving and was really hoping to bring my costs down.

After looking in to it for an inordinate amount of time(Which I wasted a lot of) I had narrowed it down to a list of a few cars.  Chief among them was the Jetta TDI.  For those of you who don't know what the TDI part stands for... it means that it is a diesel, and wow are they hard to find used.  Everywhere I turned these thing were getting snapped up as soon as they got on the market or were not in my price range.  It took me forever, but I finally found one close by and bought it.  I know that I have been saving money on fuel since I bought the car, but I am curious to know how much I am saving and how that adds up over time.  I also know that there are a myriad of other factors that should be calculated with car ownership, but right now I only want to look at fuel.

It is common knowledge that diesel engines are more efficient than gasoline burning engines.  Here are a few articles if you are interested in further study:

I want to calculate the math on just how much this increased efficiency translates to savings.

I made a quick excel spreadsheet to do all of the calculating.  I might upload it, but it is really easy to make if you are interested.  Let me know if you spot any errors.  I did this post pretty quickly! I got today's average fuel price from:

The average price for unleaded fuel I used for my calculations is: $3.859 for gas and $4.124 for diesel.

I am going to guess the range that my Altima got was somewhere between 28-38 mpg with my average probably around 32.   For the annual cost I am assuming that I drove 12,000 miles.  Here are the numbers:

Cost Per Mile of Gasoline Cost Per 1000 Miles Of Gasoline Annual Gasoline Expense
28.000                ¢ 0.138 $137.821 $1653.857
29.000                ¢ 0.133 $133.069 $1596.828
30.000                ¢ 0.129 $128.633 $1543.600
31.000                ¢ 0.124 $124.484 $1493.806
32.000                ¢ 0.121 $120.594 $1447.125
33.000                ¢ 0.117 $116.939 $1403.273
34.000                ¢ 0.114 $113.500 $1362.000
35.000                ¢ 0.110 $110.257 $1323.086
36.000                ¢ 0.107 $107.194 $1286.333
37.000                ¢ 0.104 $104.297 $1251.568
38.000                ¢ 0.102 $101.553 $1218.632

Now I have been keeping records on the Jetta since I purchased it.  My lowest tank average has been 43.49 and my highest tank average has been 49.46.  I am working hard on increasing it and hope to break into the 50's soon.  The average of all of my tanks is 46.81.  This is much better than the numbers that VW actually puts on the car.  They say to expect 32/42.  However, with the correct driving techniques you can greatly increase it as I have.  Here are the numbers:

43.000 ¢ 0.096 $95.907 $1150.884
44.000                ¢ 0.094 $93.727 $1124.727
45.000                ¢ 0.092 $91.644 $1099.733
46.000 ¢ 0.090 $89.652 $1075.826
47.000                ¢ 0.088 $87.745 $1052.936
48.000                ¢ 0.086 $85.917 $1031.000
49.000 ¢ 0.084 $84.163 $1009.959
50.000                ¢ 0.082 $82.480 $989.760
51.000                ¢ 0.081 $80.863 $970.353
52.000                ¢ 0.079 $79.308 $951.692
53.000                ¢ 0.078 $77.811 $933.736

So we can see that the difference between my Altima's yearly cost: $1447.125 and my Jetta's: $1075.826 is $371.299.  That is quite a bit of money just to chose a different car. Now lets assume that I never wrecked my car and that fuel prices stay constant.  In the next five years I would have spent an extra $1856.495 on my old car.  Thats $7235.625 vs $5379.13.  I hope to have this car for at least ten more years.  Again assuming all stays constant thats $3712.99 in 10 years. Which makes my fuel cost at $14,471.25 vs $10,758.26.  A lot of money either way, but hopefully I can bring my average tank up and increase my savings even more.

The Altima was really not that bad of a gas burner.  If we compare me to a hummer we get:

9.000                ¢ 0.429 $428.778 $5145.333
43.000                ¢ 0.096 $95.907 $1150.884

Which works out to a difference of $3994.449 a year.  Which makes $20,347.53 in 5 years and $51,442.572 in 10. What about an F-150?  I live in the south and trucks make up a large percentage of vehicles on the road around here.

Cost Per Mile  Cost Per 1000 Miles  Annual Expense
14.000                ¢ 0.276 $275.643 $3307.714
43.000                 ¢ 0.096 $95.907 $1150.884

That is a difference of $2156.83 every year.  A difference of $10,784.15 in 5 years and $21,868.30 in 10 years. I have tons of friends who drive pickups everyday without any real reason.  I don't know if I could justify the added expenditure.

Also just as something to think about.  What if you were a truck person, sold your truck, bought a fuel efficient car, and put the savings in an investment like the stock market or bonds?  You now have to think about the fact that you are losing out on the potential earnings of that money compounded over your entire life.  Adds up pretty quickly.

There are some increased costs for diesels.  They generally have a premium attached to them, you have to find a shop that knows how to fix diesels, some maintenance costs more, etc.  But they are generally considered to have a life span far greater than their gasoline burning brethren and their resale value is much higher.  In a few years you should be able to get some gasoline burning cars that are pretty cheap and have the fuel economy close to a diesel.  There are a few out there now like the Nissan Versa (2012 sedan only), Ford Fiesta, and some others.  If we really are trying to get rich slowly this seems to be something we really should consider.  Its all about the choices we make and their cost adding up over time.

Wednesday, September 12, 2012


It is hard to find motivation.  I have continuously been doing my side projects since I last wrote an article, but I somehow haven't managed to document them well.  I have a ton of ideas for articles, but I just haven't had the motivation to post them here.  A lot of these are really cool and need to be documented.  I will try and get the motivation to get them up sometime soon.