Synthetic Conversion
 

I'm changing the oil on my '77 300D on Saturday and would like to convert over to fully synthetic. I can honestly say I've used conventional oil my entire life so I have very little knowledge of synthetic, other than it lasts longer and protects longer. I currently change my oil about once a month, or 1000 miles. If I switch to fully synthetic, how long should I expect the oil to last?

If you change your oil as often as every 1000 miles, you probably won't notice any difference.

The biggest difference, I have noticed, is the synthetic oil has less sludge build-up with extended oil change intervals. We are talking more along the lines of 8000+ miles though.

I've been using the Rotella synthetic in the SD for the last three years. I change it every 5K. The oil analysis at 5K is just about right for soot. It runs close to 1% at this interval.

I'm sure others will argue that you can go longer on synthetic. I won't disagree with them.;)

Why? Even with dino you can go 3-5 months without any issues, if you drive 1k a month.

The problem with the older engines is soot loading. I wouldn't take a 617 past 5k miles without sending a sample to the lab. However if that sample comes back fine I bet you could go 6k miles or 6 months.

Why are you changing your oil ever 1000 miles now? In general, conventional oil should be good for about 3000 miles and synthetic should be good for around 5000 in your car. I currently use Mobil 1 5W40 in my cars with a 5000 mile interval.

Kruger,

10,000 miles. I have been doing this for 15 years and 165,000+ miles in my 300SD and it runs about the same as 15 years ago and doesn't burn any oil. I have been using Mobil I Synthetic.

What more proof do U need?

P E H

On my 123 the factory suggested interval is 5,000 miles with dino oil. In fairness that's an average (and your results may vary...blah, blah) but it seems like you are seriously undershooting the change interval at 1,000 miles. I converted to fully syn oil about 10 years ago and have had zero problems. If you're in the cold, white North the syn oil has the added benefit of slightly easier starts. I'm with PEH in that my drain intervals are 7-10,000 miles depending upon the cold starts vs highway miles. If you use syn and change every 5,000 you should be VERY safe.

Dino oils are much better than they were when most of our cars were built so if the manual says 5,000 then I would think that's fairly safe with any Diesel rated oil. 1,000 mile changes you could probably get away with any kind of oil. I go 5,000 mile changes even though I'm pretty sure the oil is still good, I'm more concerned about soot in the oil and testing is fairly pricey (more than just changing the oil). Syn isn't going to get rid of any soot in the oil but cold starts will be easier and some of the better ones last almost forever (your mileage may vary:D ).

So back to your question, if you only drive 1,000 miles a month then I would change the syn every 6 months or 5-6,000 miles.

I plan to go 7,500 with Delvac-1 (yup, I found it at a truckstop). :D

:cool:

Thanks for all the advice guys. I only change my oil every 1000 miles for piece of mind. It's not like it takes that much time or money compared to the cost of wearing parts. But I'm going to switch to synthetic this weekend - that'll save some changes :)

There comes a point where the concern for wear on the engine parts drives a man to procedures that are far beyond what is necessary to ensure longevity in the engine.

Please read post #6, of this thread, again, and determine if the above paragraph applies to you.

mobile delvac 1300 isnt by any chance synthetic? i wanted to stick to dino because i heard syntetic leaks easier in the old 671's.. im not starting an oil discussion i just want to know. plus it came in one gallon jugs . how many quarts do i put in my car.

Well, here's my angle...
 

Well - good for you, changing your oil every 1,000 miles - that is a bit spendy, buy that is the best thing you can do for your car. And most people don't do it. The problem really isn't the oil breakdown - it is soot in the oil, and in changing the oil often, your are really rinsing the soot out of the engine. My 123 loves 0-30 in the winter! Synthetic oil seems to be a bit better right at start-up, and in cold weather... So - keep on changing your oil! If you think the cost of Synthetic oil is too much, use dino oil - it won't break down in that short length of time. The amount of soot generated in a engine will vary on the age and condition of the engine. Mine has 280,000. miles on it, and it gets a lot of soot by 2,000.miles... ~Levon~

You will notice a great smoothness when its very cold outside. I use Amsoil and the engine has much less "rattle" than when on the natural stuff. Synthetic also handles the soot load much better than the natural stuff.

How much soot, in percent, does it get in 2,000 miles? Have a test to show us?