synthetic oil

I sold a race car to the engine shop manager over at Roush Racing a few years back. He was kind enough to share with me the results of a pretty neat test they performed. They compared most of the different popular conventional (oil does not come from dinosaurs) and synthetic oils available to consumers. They ran all the different oils in their own respective test motors (yes Roush has too much money) for the equivalent of the number of hours that the average American would rack up driving 45,000 miles. They ran the motors for 1100 hours if I remember correctly. Equivalent to a driver running his car for roughly 1 hour a day over the course of 3 years. The motors were all ran in such a fashion to as closely as possible, replicate real world driving conditions. Every so often, a very small oil sample would be collected and sent to a 3rd party lab for complete chemical analysis and metal/metalloid content. Most internal combustion motors are composed of around 15-20 different metals/metalloids and other various insoluble’s that come in contact with the oil. As oil is left in a internal combustion longer, the metal/metalloid counts can normally be observed to increase over time and is a good indicator of well an oil performs and protects. Some other tests that Roush conducted on the various oil samples were High Temp High Shear, TFOUT (thin film oxygen uptake test), and NOACK viscosity tests. The NOACK tests are notably interesting because they test an interesting characteristic of the oil that evaluates its inherent tendency to become more viscous as it breaks down over time. As oil reaches a specific temperature, it’s light weight molecules begin to evaporate leaving behind the heavier weight molecules. This effectively increases the viscosity of the oil, and increases the consumption of the oil.

Anyway, to make a long story short, the synthetics won hands down. Now that’s not a surprise, but some of the following may be to some. Aside from all of the chemical/scientific analysis of the various oils, they also evaluated the wear to the motor, specifically the cylinder walls, outer radius of the rings, bearings, journals, and valve guides. The cylinder walls were profiled with a tool called a profilometer before and after the tests. It’s a diamond tipped stylus that is dragged along the surface (usually upwards) of the cylinder wall. It can measure to one millionth of an inch (0.000001”). Using the profilometer, you can determine the following; RA (roughness average), RPK (peak height), RVK (depth of the valleys), RK (average core roughness depth), RMAX (highest peak-to-valley measurement taken from five samples), and RZ (mean highest peak-to-valley measurement taken from five samples). A surface with a low RK value and high RA value will properly suspend the oil within the crosshatching on the cylinder wall and will all but eliminate ring/ cylinder wall wear. Most factory cylinders are finished to between a 15 and 25 RA. Some of the motors that were run with the conventional oil, measured below a 10 RA after the 1100 or so hours. Anything below 10 on a factory ring will allow greater than normal blow by. The synthetic motors showed little change in the RA, in fact the motors that were run with Mobil 1 and Castrol Synthetic showed hardly any discernable change in the RA before and after.

The motors that had been run with conventional oil showed a significant reduction in the RA values and a significant decrease in the RPK values, especially when measured on the thrust sides of the cylinder walls. In other words, the cylinder walls were showing significant wear. The top 3 synthetics they tested (Mobil 1, Castrol Synthetic, and Redline Synthetic in that order) showed almost zero change in the profilometer before and after results. In other words the cross hatching from the factory on the cylinder walls was still virtually the same as it was before the tests were performed. This was evidenced by the excellent RA, RPK, and RK values of the synthetics. Additionally, the synthetics showed little to no bearing, journal, valve guide, and ring wear. The conventional oils showed a distinguishable difference in bearing, journal, valve guide, and ring wear as evidenced by the looser tolerances and changes to the journal and guide clearance indexed measurements before and after the tests.

F1 motors rev up to around 20,000 RPM at the top of each shift. All F1 teams currently use synthetic motor oil, but in the past not too long ago, some F1 teams still used conventional motor oil. It’s not uncommon for the bearings to walk towards the end of a race on those F1 motors due to the extreme stress caused by the high RPM’s. There were a number of documented occurrences where the motors running synthetics have had a bearing walk on them yet the motor held on to the end without catastrophic failure. Back when a few of the F1 guys still used conventional motor oil, they too would occasionally have a bearing walk on them, but with one clear difference, their motors immediately grenade. Now you would be hard pressed to find and race team that does not use synthetic motor oil. And you don’t have to have a race car to reap the benefits of synthetic. It has proven to significantly reduce wear, reduce friction, and significantly decrease the chances of catastrophic engine failure due to something going wrong. And you don’t have to change synthetics every 3k like you do conventional motor oil. The tests performed by Roush (and many others over the years) have shown that synthetic oil was still 99% ”intact” after 6k miles, effectively doubling the oil change interval as compared to conventional oils. These are the reasons to use synthetics. A few extra HP is just a nice little fringe benefit.

I currently use Mobil 1 5w30 in my mustang. i use it in our 2000 Grand Marquis, but i am gonna experiment a little and try some GC (German Castrol) 0w30.

bdcardinal said:

I currently use Mobil 1 5w30 in my mustang. i use it in our 2000 Grand Marquis, but i am gonna experiment a little and try some GC (German Castrol) 0w30.

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The German(brown) Castrol 0w30 is a very good oil as well. I've seen a bunch of oil analysis reports and they were very good all the way to 10k miles. Very little indication of bearing wear (lead) and very little indication of valvetrain wear (iron).

I think it's only like 30 cents more than Mobil 1 at my local Autozone.

ya, its highly recommended on BITOG. I wouldve liked to have scored some green GC, but i think thats almost all gone. the only thing that sucks about GC is that you have to go to AutoZone to get it.

i have heard that if your car is a little bit older that its a good idea to do a half half mix of sinthetic and regular oil for a start before you make the switch to full sinthetic.. is that true?

Yeah, unfortunately the GC is hard to find here in the states.

What the guys that say the using synthetics is "pissing" your money away fail to understand is the significantly reduced oil change intervals and most importanty the scientifically proven vastly superior protection provided by synthetics.

Say you drive you car 15,000 miles in one year. At roughly $3.00(with tax) a quart for converntional oil, and performing 5 oil changes within that year with 5 quarts each change, you would spend $75 a year on just the oil. Let's say you were to use Mobil 1, GC, or another top quality synthetic, you would only have to change you oil at a MAXIMUM of twice within that year. At roughly 7.50 a quart for synthetic, and performing the 2 oil changes within that same year, you would spend the exact same amount of money on the synthetic. I take pride in owning a Ford Mustang and I take pride in maintaing my vehicles to the best of my ability, and I will GLADLY pay $75 a year to provide my motor with a vastly superior oil that will give it a much better service life, will keep the oil temps down, and will give me a slight performance increase.