Is this still true

[GROUCHO MARX]

This is from an '88 Chilton's Manual for a Honda Civic:

"If synthetic oil is used, it should still be replaced at regular intervals as stated in the maintenance schedule. While the oil itself will last much longer than regular oil, pollutants such as soot, water and unburned fuel still accumulate within the oil. These are the damaging elements within a engine and must be drained regularly to prevent damage"

 

[rchavis]

Somewhat ture. Remember in 1988 Syns were still new to most machanics, and oil filters were and are still made of mostly paper. Now with a good filter(Mobil, Amsoil etc). then you can extend you drain interval. Also in 1988, Car complanies were still recommending 3000 mile oil changes as today it's 7500 miles. All oils dino and syns have improved since. So it's relative to the time of printing of the manual.

 

[guile]

This is exactly why I don't feel comfortable with extended oil drains. Chemicals will build up in the oil; and chemicals such as fuel and water will pass right through the best oil filters, right along with the oil. Of course I know it depends on the type of driving your vehicle is submitted to; me short trips (10< miles) and a lot of stop/go driving, thus these pollutants are never completely burnt off.

 

[labman]

A lot of that has to do with the type of driving you do. After an all day drive on the interstate in the summer, I doubt their is much water or fuel left in the oil, even any ethylene glycol may be gone. The filter should stop the biggest chunks of anything solid. I am sticking with 3K dino, because I am heavy into short trips. Synthetics and long drain intervals show some great UOA's here. Match the oil changes to the driving.

 

[TooSlick]

Groucho,

The primary reason why cheap petroleum oils have to be changed frequently is that they rapidly degrade from heat and oxidation. In addition, they are normally formulated using a low level of additives to save money. Often the quality of additives they use is also not that great.

PAO/Ester synlubes are much more resistant to heat and oxidation and they are formulated with significantly more robust, 11-13 TBN, additive chemistries. They are able to neutralize acids much longer and are able to harmlessly suspend and disperse more contaminents.

In a properly functioning engine, most of the water and fuel simply evaporate. Silicon is rarely a problem unless you drive on dirt roads.

I've probably averaged 12,000-15,000 mile change intervals over the past 25 years and never had any lubrication related issues. Average drain intervals all across Europe are up to about 10,000-12,000 miles, with ACEA A3/B4 quality synthetics and synthetic blends.

TS