Royal Purple - Synthetic Oils and Fuel Economy

Rex Roy
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Every driver likes getting good fuel economy. However, some drivers are willing to, ahem, go the extra mile to pursue better mileage.

The basics behind getting better mileage from the vehicle currently in your driveway are simple; decrease rolling resistance, improve aerodynamics, reduce weight, and improve the powertrain's efficiency.

Proper tire inflation helps minimize rolling resistance. Help your vehicle's aerodynamics by not driving with luggage carriers, bike racks, and other non-essential items hanging off the vehicle body. Unload the trunk and cargo areas of unnecessary gear because additional weight makes the vehicle harder to accelerate from a stop. These are all low- or no-cost, well-duhh basics.

Improving the efficiency of your vehicle's powertrain costs something and takes some effort, but from the investigating we've done, it can help improve mileage as much as seven percent.

The simplest change to make regarding improved powertrain efficiency is to switch to a synthetic engine oil at your next oil change service. Independent test data commissioned by Royal Purple synthetic oil shows that just this change can improve fuel economy 4.5 percent.

The mpg improvement comes from reducing the internal friction of the engine. Generally speaking, this reduces internal engine temperatures and also provides a slight increase in horsepower and torque. Why do you think that Chevrolet has recommended Mobil 1 synthetic oils in the highest-performance Corvettes (including the new ZR1) for decades?

While you're considering an oil change, you may also want to switch to a new type of oil filter that can help dramatically extend your oil change intervals. We covered the MicroGreen two-stage oil filter earlier this year and have been using them on a couple of test vehicles. So far, so good. With this filter and a high-quality synthetic such as Royal Purple, you should be able to drive a minimum of 12,000 miles to a maximum of 25,000 miles on the same new oil you install at this service.

Engine crankcase oil is not the only lubricant that impacts your vehicle's powertrain. The lubricants in the transmission and differential can also impact fuel economy. Royal Purple (as well as other manufacturers) make oils specifically designed for automatic and manual transmissions, as well as differentials. Reducing friction in these components also impacts fuel economy by several percent. Changing these oils could lead to an mpg boost of an additional 2.5-3.0 percent.

Now time for a personal anecdote; back in the 1990s, your author owned a speed shop in suburban Detroit. The shop, PowerCurve, featured a DynoJet chassis dynamometer that enabled technicians to measure total powertrain torque. An additional feature of the dyno was that it could measure coast-down resistance (how quickly the dyno decelerated when the vehicle's powertrain was coasting). Because of our racing-centric clientele, we often did full synthetic oil change-overs, and techs always measured a decrease in rolling resistance when we did pre- and post-change dyno coast-down runs. The change to synthetic oils also resulted in nominally higher torque output.

Making minor changes such as these can help you boost the economy of the vehicle you're currently driving. Keep in mind that even a 10-percent gain in fuel economy in a vehicle that currently achieves 20 mpg will only be 2 mpg. This change can be hard to casually observe, so you may want to keep a mileage log to track the improvement. However, over the course of 12,000 miles, this 2-mpg increase will save approximately $150 in fuel costs (based on $3/gallon). Looked at over the long term, going the extra mile to achieve improved efficiency is worth the effort.

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