Synthetic Engine Oil
by Jim Kerr

Synthetic engine oils have been around for decades and work very well. Just like many other products, they are always being improved and boldly marketed. Motorists may not be sure if the manufacturer's advertised claims about the synthetic oils are correct, or if they are just hype to entice buyers to the more expensive lubricant. Recently Pennzoil came out with a new synthetic oil with their new special additive "Pennzane". I thought I would try the Pennzoil Synthetic oil in one of my own vehicles to see how it performed.

Let me start by saying I wasn't expecting miracles. Even though the "Pennzane" oil additive is a synthesized hydrocarbon fluid and has been used by NASA since 1989 as a lubricant for space-going mechanisms, I didn't expect to launch my pickup truck into orbit. I also didn't expect the synthetic oil to be a "Mechanic in a Can" and repair or eliminate any mechanical problems with my truck's engine (it has none I am aware of).

What I was expecting was better engine protection during extreme temperatures, both hot and cold, and maybe a slight change in engine performance. I was also interested to see if the synthetic oil would make any difference in exhaust emission levels.

Snap-On four gas analyzer
An exhaust gas analysis of the truck shows the hydrocarbons levels slightly high, but the truck performing well otherwise.

chassis dynamometer
Operating the truck on the dynamometer enabled a baseline horsepower and emissions test to be done while driving at 100 kph.

Pennzoil Synthetic Oil with Pennzane
After running some preliminary tests, the old oil was drained and the engine filled with the new Pennzoil 10W-30 Synthetic engine oil with "Pennzane" additive.
I started my investigation by running a baseline test on my truck. It is a full size GMC two-wheel drive pickup truck equipped with a 5.7 litre V8 engine and automatic transmission. The truck has had routine maintenance since new and with 30,000 kilometres on the vehicle, the engine has had a chance to break in completely. I hooked the truck up to our chassis dynamometer and drove it until the engine, transmission, and axle were completely warmed up. I was then ready to do some measurements.

The truck was due for an oil change, but I wanted to take an emissions sample and horsepower measurement before switching to the Pennzoil synthetic. I used a Snap-On four gas analyzer to check the exhaust emissions while driving the truck at 100 kph on the dyno. The readouts for carbon monoxide, carbon dioxide, and oxygen were fine, but the hydrocarbons level was a little higher than I expected for a vehicle equipped with a catalytic converter. Perhaps the converter had degraded in performance because of using gasoline with a high sulphur content, or the engine could be running a little rich because of oxygen sensor contamination, but I was just interested in a base line measurement. I would have to check out the hydrocarbons level later.

Next, I took a horsepower readout from the dyno. Rear wheel horsepower is always much lower than advertised horsepower rating but I wasn't after maximum horsepower; I wanted to see if there were any gains at part throttle driving. I set the dynamometer so it would load the vehicle with an eight horsepower load at 100 kph. This is how much horsepower it takes to drive a typical full size pickup down the highway at that speed. Then I measured the throttle opening by reading the data from the truck's engine computer. It all sounds high tech, but it is really very simple to do if one has the equipment, and I felt it was necessary to take these measurements to make my evaluation as objective as possible.

Finally, it was time to change the oil. I installed a new original equipment oil filter (same as before) and five litres of Pennzoil Synthetic Oil with Pennzane. After running the engine for 15 minutes to ensure the oil was on all moving parts inside the engine, I stabilized the engine temperature and ran the truck at 100 kph on the dyno to check the throttle data. It showed no significant difference, which would indicate that there was no horsepower increase at highway cruising speeds. It is important to remember that horsepower readings are affected greatly by engine temperature, underhood air temperature, and humidity. I tried to make the two horsepower tests as similar as possible but there is room for error. What I can say from my experience, is that synthetic oil will not give you a BIG horsepower increase.

Next, I retested the exhaust emissions levels. Again, I found no real differences. There seemed to be no reduction of emissions by switching to synthetic oil in a good running engine. The tests confirmed what I suspected; I would have to test the oil over the long term to see if I could find any benefits.

The next test came a week later. I took the family on holidays through Montana. It was hot! The temperature exceeded 40 C and the speed limits are high. The truck performed flawlessly, and did not use any oil in 2000 kilometres of driving. I also notice the oil pressure gauge remained in the normal range with the engine idling, instead of dropping to the low end of the scale as it has done during previous hot weather driving. This test was definitely subjective, but it reinforced my belief in one of the advantages of synthetic oil; Synthetic oils don't change viscosity as much when they get hot and therefore they can protect the engine better.

Several cars require synthetic engine oil to meet the manufacturer's warranty requirements. Typically, these are high performance vehicles that generate a lot of heat in the engine during spirited driving. Synthetic oils provide the extra protection during hot engine conditions.

It was only a few weeks later that I was able to check the oil performance during cold weather. While we have not reached the frigid temperatures of winter, the temperature has already dropped to -14 C where I was driving. I noticed the engine cranked quickly, and the oil pressure rose immediately upon starting the truck. This seemed to be a faster rise in oil pressure during cold temperatures than I previously had with regular oil. The synthetic oil did not seem to thicken as much during cold temperatures and therefore could provide better lubrication during cold weather starting. While I realize this is very subjective evaluation, I did place one sample of synthetic oil and a similar one of regular oil in the freezer and found the synthetic oil did pour easier after being frozen for a few hours.

Finally, after five thousand kilometres of driving, I completed my evaluation by re-testing the horsepower output and exhaust emissions levels. There were no significant changes from my initial tests.

So what are the advantages of synthetic oil? It would appear the manufacturer's claims of better engine protection at extreme driving temperatures are the key advantages. If you work your engine hard, drive in extreme heat, or have cold weather starts, then synthetic oil should protect the engine better.

The disadvantages of synthetic oil are mainly the cost of the oil. It is more than twice as expensive as regular oil and still needs changing at the same mileage intervals as regular oil. Synthetic oils may not break down as regular oils do over time, but one of the main reasons for changing oil is to remove crankcase acids and contaminants caused by the combustion process. Synthetic oil gets "dirty" just as regular oil does.

Synthetic oils cost more, but the cost is insignificant compared to the cost of engine mechanical repairs. If your climatic conditions or driving style warrant the use of synthetic oil, then it is worth the few extra dollars.

As for my truck, I plan to operate the truck with synthetic oil over the winter to gain personal experience in starting performance at -40C temperatures! Real life testing can sometimes be tough on the tester and the vehicle!

Jim Kerr is a master automotive mechanic and teaches automotive technology. He has been writing automotive articles for fifteen years for newspapers and magazines in Canada and the United States, and is a member of the Automotive Journalist's Association of Canada (AJAC)