Transcribed from Central Ohio MG Owners Club Tech Session, Oct 20 2007.
George Morrison, an independent STLE Certified Lubrication Specialist from AV lubricants Co. presented an interesting and informative tech session with approximately 25 COMGO members in attendance, with questions and answers on lubrication an issues regarding our British cars.
George started by stating that lubrication technology and terms have changed greatly over the last five to ten years. Formerly there were two types of material for lubrication: Mineral based, and Synthetics. Currently the mineral based products have grown and are classified as Group 1, Group 2 (higher refined than Group 1), and Group 3 (higher refined than Group 2, with some properties nearing that of synthetics, and can legally be labeled as "synthesized", or synthetic). The pure Synthetics are classified as Group 4.
In the numerical classification system, e.g. 10w30, the "W" originally stood for winter. As most of us know, the numbers stand for the material's viscosity. In regards to mineral oil, when mineral oil gets cold, it becomes thicker, and has a higher viscosity. The base weight, in this case the 10. When the oil is manufactured it begins as a base weight "10 Weight" oil. In order top be a 30 Weight with greater viscosity when the temperature increases, plasticizers (which were described as microscopic plastic coils) expand, and the result is reduced thinning. The lower the base weight, the more plasticizers (longer coils) needed for a given increase. But keep in mind that the plasticizers will break down over time, and with heat, and the longer the coils, the more susceptible they are.
In regards to (pure) synthetics, when temperature decreases, the viscosity remains about the same. As the temperature increases (oil is tested up to 200 degrees), the viscosity still remains about the same, so the differences in synthetic weights is generally just labelling and marketing for warranty and perception. A synthetic 10w30, or a 5w30 is basically a 30 weight oil. Also, synthetics have a better attraction to metal and adheres, or coats, the surfaces better over longer periods of time.
When questioned, George recommended Group 4 synthetics for our cars, or in fact any vehicle for which we care for, or plan to keep for a long time. His reasoning in part was:
- As described above, synthetics have a better attraction for metals. For vehicles that may not be started for extended periods of time, a coating of oil remains on surfaces much longer than mineral oil.
- When a piston is at top dead center in the combustion cycle there is less burn off at TDC with synthetic oil, leaving a film higher up on the cylinder wall, as a result there is less blow by (more power, and less contamination of the oil in the crankcase).
- Mineral oil produces ash when burned off, adding to the particulate matter, and acid contamination of the oil which affects it's lubrication capabilities.
George continued by stating that since synthetics don't get as contaminated, and doesn't wear out as mineral oil does, as a result you can go longer between changes particularly if you use a high quality oil filter. Most quality filters can go up to 10,000 miles, he says Amsoil's AEO line tested best on the market currently. Even though synthetics will remain cleaner than mineral based oils, it will become dirty due to ingestion of dirt into the engine through the air intake tract. An oil analysis, which usually costs less than $20, will report the contamination levels and thus the proper oil change intervals.
Special note: While oils are classed into four groups as described above, the group classifications are not listed on the product labels. The only way to determine what classification an oil is, is to carefully review the product's material data sheet (if you know what to look for). George did state that Mobil 1, Amsoil and most of Redline's oils are all Group 4, while all other readily available synthetics he has tested were actually Group 3 mineral based oils, labeled as synthetics.
Other notes of interest:
- He felt that the discussion regarding the removal of ZDDP (zinc diophosphate) from mineral based oils as a cause of engine failures was not accurate. While manufacturers have removed ZDDP (by government mandate), the addition of better quality additives to replace it has improved their lubrication capabilities.
- The use of synthetics should not result in leakage around new gaskets and seals. He did say that if an engine had been run on mineral oils for any real length of time, perhaps you should install new seals when you change over, because additives in mineral oils artificially swell seals to which helps to prevent leaks, and that synthetics don't have the same additives.
- Synthetics are fine for break in, every new Corvette (and others) are broke in on Mobil 1.
- He does not like the use of ANY additives to oil, and likened it to adding an extra egg to a cake recipe after the cake is baked. The additive packages in the oil are engineered to chemically work together, and any additive can reduce their effectiveness.
- The use of synthetics in your driveline may result in an increase in fuel mileage, and a 1%-3% increase in horsepower to the wheels
- If you vehicle has an oil bath air filter, you should not use synthetic oil in it. Synthetic oil is chemically stable, and will not "grab" the dirt out of the air like chemically unstable mineral based will.
By Jim Nibert and Rob Meier