The Age Old Question... Synthetic or Mineral Base Oils?
By BRETT WINBERG

Question of the day... what about the effects of changing back to a mineral oil from synthetic oil? We can better tell you about some of the disadvantages and advantages of synthetic oil and let that be your guide in your decision making process.

However, from personal experiences, I have noted that changing back to mineral based oil from synthetic oils can have a negative impact on an engine.

For example, a colleague of ours has been running synthetic oil in his Toyota pick up truck for quite some time. He had dropped it off at the local quick lube to have his oil changed but had forgotten to mention that he had been running a synthetic oil. So as a normal day goes at the quick lube, the synthetic oil was replaced with a normal 10w30 in his crankcase and nothing was ever mentioned about the synthetic oil.

After traveling for about 250 miles, the engine had developed a severe rod knock. After checking the oil level, we helped him disassemble the engine and all the bearings were worn down to the copper level. While this was a strange coincidence, our only logical conclusion... the difference between the oils were the culprit, since we found no other evidence of internal failure.

We realize people change from synthetic based to mineral based oils on a regular basis without any further problems. However, you may wish to consider the following items to guide your decision on changing from one to the other:

• The year of the engine or vehicle - Does the engine have a neoprene rear main seal and or valve stem seals? If the vehicle is a pre-1990, this may cause a leak in the rear main seal and or blow by in the valve stem area. The base products between synthetic and mineral oils are different and can cause seal damage.

• Oil is not interchangeable - You should stay with the same brand once you start with a particular brand. Different base materials and additive packs all vary from brand to brand. It is considered dangerous to switch brands or top off with another brand. You must also assure the correct API code (example CI4, SH4, etc) since certain engines call for API codes based upon the base stock products of the oil.

• Stay close the OEM recommended viscosity - Diesel applications run 15w40 for a reason... because of the viscosity of the oil. If you run a 10w30 in a diesel application, you cause major bearing wear and/or damage. You need the film strength of the 15w40 to protect from the higher pressures that a diesel engine creates internally. A diesel runs at 20:1 compression where an average gasoline engine runs at 8:1 compression. This causes the oil film strength to break down and that is why the correct weight is important. And of course, diesel engines require different API ratings than gasoline engines do.

• Synthetic base stock vary - Depending on the particular stock, synthetics are generally made through a reaction process.  This reaction process significantly improves the consistency of the base stock and its uniformity. Mineral base stocks, on the other hand, are obtained through a process of distillation and react differently.

• Esters are bad for your engine - Because of oxidation stability issues, ester based oils can have harmful side effects. True synthetic oils are supposed to contain PAO's (Polyalphaolephins) however, remember PAO's are very expensive.  First of all, most semi, fully or blended and 100% synthetic oils use a recycled motor oil base, which in return uses a hydroisomerized petroleum base, or are Ester based mixes, which is very hard to control oxidation and stability. 
  
  The oil companies are allowed to call themselves 100% due to the "process" set by the petroleum industry. These oils do not act like or contain the characteristics of  a true non-ester based synthetic oil. Because they contain crude oil, the oil's lighter less dense ingredients boil off during combustion and oil operation temperatures running as high as 340 degrees within the piston skirt area, make the oil thicker and more viscous as it starts to break down somewhere around 15,000 miles.
  
  Secondly, many of the chemicals found in petroleum base stocks begin to react under extreme heat, which forms sludge, gum and varnish. PAO's do not have this problem and are more stable than the ester based counterparts. Make sure the synthetic oil you use contains a pure PAO bright stock base with no esters.

Now, if you have been running a mineral base oil and want to change to synthetic base oil, here are a few pros & cons below.

The synthetic oils have a few advantages over the mineral base oil such as:

1. Higher Flash Point
2. Lower Pour Point
3. Thermal Stability
4. Lower Friction
5. Higher Shear Points

But also has some disadvantages such as:

1. Higher Cost
2. Toxic
3. Hazardous Disposal
4. Mix ability
5. Seal Compatibility

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