I have been a fan of diesel vehicles since my decision to go from high horsepower to high efficiency when I grew up. It was hard in many ways, the first VW Rabbit I looked at didn’t impress me. In fact I thought it was so ugly I almost walked away. Driving it didn’t help either. When you are used to muscle car performance an economy car just isn’t fun. About the only thing I liked about it was the cool factor of the small diesel engine with the big diesel chatter. Since that time I have actually grown to like them as they are hard to beat when it comes to mileage.

Since I had to retire my diesel Mazda pickup an replaced it with a gas extended cab Mazda truck I have suffered from a major drop in mileage. My old diesel truck would easily get 30 mpg in combined driving. If I stayed off the pedal I could push it to about 35. A gas Mazda running real well gets about 25 pushing it. These are my real figures as I check mileage everytime I fill up.

In the long run I plan on dropping a diesel engine in an extended cab Mazda, but that is a ways in the future. In the meantime I needed to push my mileage. My truck runs well but it did need a tune up. I installed new spark plugs, wires, air filter, distributor cap, rotor, and changed the oil to a synthetic blend. I will install a high output coil in the future. I then put full synthetic gear oil in the transmission and rear end. The synthetic gear oil is more than twice the cost of conventional oil, but I have found it pays for itself.

After the tune up and switching to synthetic oils I tested my mileage. I compared unloaded mileage before and after and had a 3-4 mpg gain. The mileage gain was not from just the synthetic oil, some was from the tune up. But I would wager half that gain was from the synthetic oil. That pushes my mostly highway mileage to 28-29 mpg. Very good for the truck. In fact it is the best I have ever got from a gas Mazda pickup after driving several over the years.

It has sold me on the synthetic oils, especially for the rear end and tranny where they can make the most difference for the least cost. It still wasn’t cheap. It took a little over three quarts for the tranny and a little under two quarts for the rear end. Five quarts of oil at $11+ a quart adds up, but over the life of the truck it will easily pay for itself and save some money.

The outcome has convinced me to go synthetic in all my vehicles. I would like to see what would happen in the ton truck that gets 8 mpg or the Jetta that can already get up to 45mpg. Another benefit is the smell. Any mechanic can easily distingiush the smell of conventional gear oil. It has a fragrance that lingers. The synthetic oil doesn’t have that smell.

For the motor oil I went with Trop Artic Synthetic blend. I think it is a good combanation of low cost but still good oil. It is the cheapest synthetic blend in my area, the closest competitor is the Motorcraft Synthetic Blend which I switched from. There may be better oils, but pretty soon the cost of an oil change will add up to the cost of a replacement motor if the better oil really did make that much difference.

The Trop Arctic goes on sale at Orschelns every year so I stock up. The Motorcraft oil runs over a buck more a quart. If I used a Mobil synthetic blend it would be over twice the cost. It starts adding up and I have to draw the line somewhere.

So for anything I do the math has to add up or have another benefit. Figuring a 2mpg gain over conventional gear oils the synthetic oil will pay for itself in under 6,000 miles. After that it is saving you money at the tune of roughly $10 every 1000 miles. Not too bad.