I heard that you can save your synthetic oil, let it settle out over a few weeks and you can use it again. I got this from a diesel mechanic last week. I thought that the oil would break down or contain contaminants?
Several folks have said that changing synthetic sooner then 30K miles is a waste of money too. Is that true?
I have also heard that when not using a remote bypass filter, you can do fine with changing out your oil filter every 15K miles.

So you dump the oil after 30K, let it settle out and then its ready to go again?

This thread is not here to incite a brand war...just looking for some answers with some factual proof. I would love to change my oil less if it makes sense.

Scotty

 

The additives in any oil get depleted with use, letting it settle out isn't going to bring them back. Also the oil can only hold so much soot before it will hold no more, that's were a bypass filter comes in.
Important part of extended oil changes is replenishing the additive package when adding make up oil with a filter change, don't it think would be wise to stretch it too far. 15k isn't too far though, I go 10k on oil/filter changes with dino Delo.
Regular oil analysis is very important with if you want to go further. I've read of guys going over 75k without changing synthetic oil but they still add a quart or so at 5-10k filter changes and run a bypass.

 

Scotty I'd be really hesitant to believe any settling stories or reusing oil.

Based on my experience with the 305/555, which is pretty easy on oil, most likley you can do 10-15k on a quality synthetic without problems, but a $15 oil analysis test sure would help you know exactly what the best interval is.. My advice is to get some delvac 1 and sample it after 10k miles. Then you'll have a good idea how far you can go.

 

Over its lifespan lube oil will suffer, among other deterioration, additive depletion, contamination with weak and strong combustion acids, water, fuel, etc., buildup of soot as well as changes in the molecular structure of the oil itself through oxidation, nitration, molecular shearing of long chain hydrocarbons, etc. If the detergency package is doing its job, it's going to hold contaminants (including soot) in suspension, so settling isn't going to allow these contaminants to drop out. Of course, settling also isn't going to replenish depleted additives or restore the molecular properties of the base stock.

When it comes to lube oil, I'd listen to a tribologist over a diesel mechanic.

Rusty

 

What my gut feeling was and what I just read here is what makes sense. I will continue to run with 15K changes on 5W40 synthetic.

Will take a sample this change too.

Thanks for the confirmation of what I figured would be the issues.

Scotty

 

Scotty I wouldn't run 15k on just any synthetic, I'd be sure it's an extended drain synthetic that's got a high TBN and beefy additive package. I wouldn't run rotella synthetic or valvoline for that long but amsoil or delvac 1 or redline I would ..

 

Maybe I would be better off to run dino and change it more often then because the price of the redline etc is insane here.

I never bought a bottle of wine for more then 3 bucks, why would I buy a quart or liter of oil worth triple my comfort drink?



Just kidding.

 

Delvac 1 can go 4x the normal oil change when an extended life filter is used per Mobil.

 

Rusty, you hit the nail on the head. And would you believe there are guys that add used engine oil to their fuel? Not this CDT owner. NEVER! Reusing used engine oil is like eating your own waste! Just flush it for goodness sake! There is a reason they call it WASTE OIL!
(all used oil should be disposed of properly! )