Oil Changes

[bross]

FREQUENTLY ASKED QUESTIONS REGARDING SYNTHETIC LUBRICANTS

This section answers some of the most common questions people ask regarding synthetic oil. The answers here are brief and to the point. There are areas within this book that address some of these questions in more detail.

Are synthetic motor oils compatible with petroleum motor oils and other synthetics?

Yes, synthetic oils for passenger car and light truck use are fully compatible with petroleum oil and other synthetic lubricants. But, even though they are compatible it is best not to mix different brands of oil. Each brand of oil has a specific chemistry and additive package and two different oils mixed together may result in optimal performance as they were engineered to if the chemistries of the oil becomes offset by mixing with another brand of oil.

I was told that once I change to synthetic I could never change back to petroleum oil: is this true?

That statement is 100% false. You can change back to petroleum oil at any time. If running a petroleum oil you can change to synthetic oil at any time as long as the engine is in mechanically sound condition.
Do synthetic motor oils damage seals?

Absolutely not. Both petroleum motor oils and synthetic motor oils have additives blended in the oil to control seal swell, shrinkage and other engineering parameters.
Can I change to synthetic motor oil at any time?

Yes, you can install synthetic motor oil in any engine as long as the engine is in mechanically sound condition. There is no specific set cast in stone mileage that you can or cannot install synthetic motor oil in an engine, or any other component or system for that matter.

My mechanic tells me that synthetic oil is too slippery for use in engines with roller rockers and wet clutches; is there any truth to this?

Absolutely not; that is a false statement. Synthetic oil is no more “slippery” than petroleum oil. The tractive coefficient, which is a measure of the case by which a lubricant facilitates sliding, is essentially the same for both mineral oils and synthetics. Synthetic oil is more uniform in molecular structure, which reduces frictional resistance but it is not more “slippery” than petroleum oil.

Will using synthetic motor oil void my new vehicle warranty?

Absolutely not. Manufacturers base their warranty requirements on oils meeting API service quality classifications. This does not mean that the oil has to have the API starburst; only that the oil must meets the API service quality classifications (SJ, SL, etc.). The fact is that a premium quality synthetic motor oil will not only meet these specifications but also exceed them.

What about all the different viscosity oils my owner’s manual says I have to use for different outside temperatures, seasons and climates; do I need to use different viscosity synthetic oils as well?

Synthetic motor oils have an exceptionally low pour point (typically around minus 60 deg. F for a premium quality 5W-30, 10W-30 or 0W-30) and an exceptionally high flash point and high temperature/high shear viscosity value. Petroleum oil cannot come close to matching these wide operating temperature ranges, thus necessitating different viscosities for different climates. When using a premium quality synthetic motor oil you do not have to change to a different viscosity for different climates.



Why do some test results showing synthetic oils superiority state “as tested by an independent lab”? Why don’t you state which lab did the testing?

First, it is generally against most companies’ policies to release that information to consumers, as well as their vendors. It is partly due to confidentiality and partly because some labs do not have customer service departments and can’t have retail customers calling them. Instead, take a look at how long the particular company has been in business. It would be terribly hard for a company to stay in business for a long period of time if their advertising is not accurate. Also, the Federal Trade Commission takes a very dim view of false advertising and comes down hard on companies whose products don’t perform as claimed. Besides that, if the data is not accurate a competitor is likely to initiate legal action, which can be very expensive. Finally, if a person wants to, they are welcome to take a sample of the product in question to any lab that has ASTM equipment and have the tests run themselves.



Are synthetic motor oils capable of extended drain intervals?

Some are and some are not. The only way to know for sure is to go by the oil manufacturers specifications. This can also be verified by oil analysis testing at different intervals during use. There are a two manufacturers that specify 25,000 mile/1-year drain intervals and only one that I am aware of that specifies 35,000 mile/1-year intervals, without by-pass filtration. If by-pass filtration and oil analysis is used, then drain intervals can be extended until the lab results indicate the oil needs to be changed. This can be many years and several hundred thousand miles depending on the variables.



Will synthetic motor oil reduce oil consumption?

Yes, synthetic motor oils have been proven to have much lower volatility than petroleum oil as well as improved piston to cylinder sealing and superior oxidative stability, thus resulting in reduced oil consumption. Synthetic oil will not cure an engine that consumes oil due to mechanical issues. Synthetic oil should be used in mechanically sound engines. If you have a known mechanical issue, then repair it before installing synthetic motor oil.



Will synthetic oil cause the wet clutch in my motorcycle to slip?

Whether the oil is a petroleum oil or synthetic is not the issue here. As stated previously, synthetic oil is not more “slippery” than petroleum oil. Both petroleum oil and synthetic oil for automotive use has friction modifiers blended in, which are typically not compatible with wet clutch applications. There are motorcycle specific oils blended specifically for motorcycle applications with wet clutches that should be used in motorcycles. These lubricants do not have any friction modifiers blended in.

Will synthetic oil cause oil pressure to change?

Oil pressure is also directly related to flow volume. Synthetic oil is more uniform in molecular structure and provides less resistance to flow therefore in order to achieve the same flow volume as a petroleum oil, which has a higher frictional resistance to flow, it is possible that under some conditions, such as idling that a slightly lower oil pressure could be noticed, but that the oil flow volume delivered to the engine is adequate for the engine operating RPM and conditions. Synthetic oil has better flow characteristics than petroleum oil and may also cause an engines RPM at idle to increase due to decreased resistance to flow, less internal drag and parasitic losses.

Here’s another way to explain pressure and flow volume: if you have an air tool at requires 90 PSI @12 CFM, you could use a 1 HP air compressor that delivers 90 PSI, however it would not deliver 90 PSI @12 CFM, and would have to work very hard to make the tool operate, however the tool would not operate at maximum capacity due to the lower flow volume. A 10 HP compressor on the other hand would easily provide 90PSI @ 12 CFM and would not have to work very hard to do it. Pressure and flow volume go hand in hand. You can have maximum oil pressure, however if you don’t have the proper flow volume it isn’t going to do you any good. With synthetic oil, and all other engine parameters remaining equal, it takes less oil pressure to achieve an equivalent flow volume of oil than it does with a petroleum oil, and the engine doesn’t have to work as hard to deliver the increased flow volume. Often when changing to a synthetic motor oil the engine RPM may increase at idle due to decreased internal frictional resistance of rotating and sliding components.

At high engine operating temperatures synthetic motor oil will be much more shear stable and will not drop nearly as much as petroleum oil does. I recently had a friend with a jet boat with a 460 cu. in. racing engine. After one mile run across the lake with a 20W-50 petroelum oil the oil pressure went from about 45 psi down to about 15-20 psi. After changing to a premium quality synthetic motor oil and after the same one mile run across the lake the oil pressure only dropped to about 30-35 psi. That is the direct result of the superior high temperature characteristics of synthetic motor oil and its ability to resist the effects of intense shear forces.



I am using an extended drain interval synthetic oil but my change engine oil light is on. Do I have to change the oil?

Oil sensors and oil change lights do not and cannot perform spectrographic or laboratory chemical analysis on an oil (the proper method to determine an oils suitability for continued service). They typically monitor certain engine operating parameters and use an algorithm to predict when the oil light should come on. If you are using an extended drain interval synthetic oil, such as a 25,000 mile/1-year or 35,000 mile/1-year oil, and the oil light comes on simply reset it and follow the oil manufacturers change recommendations.

[bross]

Originally Posted by BikerBeagle

I'm 99% certain that oil doesn't break down 1) after a certain period or 2) simply exposed to air ...at least, none of the current plastic jugs and containers I've seen are air-tight and I have yet to see an expiration date on them.

Engine Oil Shelf Life.

I couldn't decide whether to put this in the FAQ or the main page, so it's in both, because I get asked this question a lot. Typically, the question is along the lines of "GenericAutoSuperStore are having a sale on WickedlySlippy Brand synthetic oil. If I buy it now, how long can I keep if before I use it?"
In general, liquid lubricants (ie. oils, not greases) will remain intact for a number of years. The main factor affecting the life of the oil is the storage condition for the products. Exposure to extreme temperature changes, and moisture will reduce the shelf life of the lubricants. ie. don't leave in the sun with the lid off. Best to keep them sealed and unopened.

Technically, engine oils have shelf lives of four to five years. However, as years pass, unused engine oils can become obsolete and fail to meet the technical requirements of current engines. The specs get updated regularly based on new scientific testing procedures and engine requirements. But this is only really a concern if you've bought a brand new car but have engine oil you bought for the previous car. An oil that is a number of years old might not be formulated to meet the requirements set for your newer engine.

If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. If they do meet the current standards, you might want to take the extra precaution of obtaining oil analysis before using them. An oil analysis will check for key properties of the oil and ensure that it still meets the original manufacturing specs. Of course the cost of getting an analysis done on old oil is probably going to outweigh going and buying fresh stuff. So it's a double-edged sword.
As a general rule, the simpler the oil formulation, the longer the shelf life. The following is a guideline under protected conditions:
Product Shelf Life
Base Oils, Process Oils 3 years
Hydraulic Oils, Compressor Oils, General Purpose Lubricating Oils 2 years
Engine Oils and Transmission Oils 3 years
Industrial and Automotive Gear Oils 2 years
Metal Working and Cutting Oils 1 year

The following are signs of storage instability in a lubricant:

* Settling out of the additives as a gel or sticky liquid
* Floc or haze
* Precipitates/solid material
* Colour change or haziness

Water contamination in a lubricant can be detected by a "milky" appearance of the product.

[ChevelleSSLS6]

Originally Posted by bross

Engine Oil Shelf Life.

If your unopened containers of engine oil are more than three years old, read the labels to make sure they meet the latest industry standards. I.

Newer oils have less (I forgot what it is) so it's not good on flat tappet cams in older engines. It's said that GM's engine oil additive (I think it's a break in additive, not sure) has that substance in it that will help lubricate the lifters better. Even Shell Rotella has since changed over to the newer formula.

The reason for the changeover is that that substance, despite it's ability to lubricate the cam/lifters well, is said to destroy cat converters in engines that burn oil.

In newer engines, they're pretty much all roller lifters nowdays for reduced internal friction and thus a little more mpg (how much I don't know, but doubt its much). A benefit for enthusiasts is more power, steeper 'ramp up' on the cam lobes so the valve is open closer to max lift longer, and more high rpm longevity.