Switched to Synthetic

My opinion is to use rotella or the like because of the superior particulate suspension. My sense (don't know for sure) is that a 79 diesel will make the amsoil just as dirty just as fast as dino oil. Particulates in the oil are a source of early demise for diesels. My opinion is dino oil changed every three thousand miles is a sufficient and more economical choice.

The high idle could be a lot of things, e.g collapsed motor mounts preventing the throttle linkage from returning all the way, rack damper.adjustment etc.

YMMV

I tried synthetic, Amsoil and Mobile One in my 300 TDT when it had about 350,000 miles on it. I just reinstalled the engine after having it remanufactured. I am not sure if it was the synthetic oil, but my engine, which had remained stable for a long time, went rapidly downhill after I switched to synthetic.

I asked the owner at the place that remanufactured my engine, Metric Motors in Canuga Park, CA if he would recommend synthetic oil. He does not recommend synthetic. He feels that since the diesel engine puts a lot of carbon into the oil the extended driving distance between oil changes with synthetic is not a good idea.

I put synthetic oil >

I was a bit confused by your message, in that if you had just had the engine overhauled, then the engine would not have been "stable for a long time" and therefore, the deterioration may have been due to some factor other than the choice of oil, e.g., a bad overhaul, etc.

Ask the big rig truck drivers... they got the most mileage under their belt.

Synthetic is supposed to be far superior keeping carbon in suspension. New Mercedes engine recommends 7500 miles per oil change... synthetic required...

as for 350,000 miles... come on! Getting 350,000 miles on an engine that you are not original owner from beginning is already great.

Based on what I read synthetic oil *does not protect your engine any better* it simply breaks down less over time and requires fewer additives to maintain its viscosity. I can find no claims for improved particulate suspension in any oils other than rotella or delvac.

Diesels generate much more soot and acidic combustion blow-by in the crankcase. Turbochargers subject motor oils to high temperatures and are more prone to form engine deposits. High milage engines generate more blow-by as well. which is why changing oil in diesels more frequently is better, it protects the bottom end of the motor.

So, according to the above you should still change your oil filter at the frequency of the manufactures specification regardless of the type of oil. As long as you are changing oil at the recomended intervals, synthetic is not better (unless of course the manufacturer requires synthetic, google the FSS law suit against mercedes for an example)

Anyway dino vs. synthetic often degrades into a religious debate and I just don't have time for religious debates. I simply am saying what I would do with regard to oil changes on a car of that vintage.

Particulates are to be controlled by the oil filter... There is zero way to completely trap the particulate that it would clogged up the filter and starve engine of oil.

By Mercedes design... those particulate still in suspension are not that harmful as you would think until the point of high concentration.

[Amsoil Flush]

How does one determine "success" with a particular brand of motor oil? By the engine not failing when the stuff is in the crankcase?

But I understand what you mean about erring on the side of quality.

Geoff

-- "Wit goes for the jugular, not the jocular." -- Florence King

By "success" in this case, I mean that my engines get very high time between overhauls, without breakdown or failure, thus attesting to the efficacy of the products I use. I can say, conversely, that in my younger, less enlightened days as a Pensoil devotee, I did not have such success.

I am using the Amsoil 20-50, and am very pleased with it. I agree with all your statements regarding the superior lubricating qualities.