Oil change intervals with synthetics?

[RWB]

I have been considering switching to synthetic oil for my Duramax. I currently use dino-Delvac and change my oil every 3000 miles. Since changing sythetic oil every 3000 miles would be WAY too expensive, how often do you guys running synthetic change your oil. Do you use analysis and/or regular filter changes to extend drain intervals? Thanks for the info.

[Diesel_Lawyer]

The owners manual and warranty information state that the oil must be changed every 7500 miles or once a year whatever comed first.

I guess that means you could extend the drain intervals up to 7500 miles but no more.

[chuntag95]

RWB,

The answer is yes to both. Doing a filter change at normal intervals and doing analysis so you know what's going on is the safest way IMO. I just sent off some oil with 7500 miles on it. Another thing you can do is go to an oil by-pass system. This basically has 2 filters. One like your normal filter and one that gets much smaller particles to keep your oil cleaner. You can find a lot of info from Amsoil or Redline. I like synthetics due to the ability to survive much harsher conditions in the event of a failure. I had a gas engine overheat to the point of seizing due to a stuck thermostat. I was running Mobil 1. Once it cooled, it started backup and still doesn't burn any oil. The oil was not burned, but all the gaskets were cooked. :eek: I have run synthetics in everything I own since then including my lawnmower. :D Do the research on the products and make up your own mind as it is your investment you are protecting. I use Amsoil and have been happy with it. They also back up their products with warranty for extended drain intervals. Just my .02 and I am sure others will give theirs too. ;) That's the great thing about TDP. :D

[Alli-max]

I run about 10K on Rotella Synthetic. Had 2 analysis' done and it is fine for my driving habits.

[ChevysRus]

Hey there, I use the Mobil Delvac Synthetic 5W-40(don't confuse this with Mobil 1) and I am going to be splitting the difference and change every 5K

It is a little more expensive, but so is the repair work after warranty. Since I plan to be buried in this truck one day, then using the Mobil Delvac Synthetic is "cheap insurance" IMHO.

If you are not planning to keep the truck forever then run the dino Mobil Delvac and as the song goes 'Don't worry, be happy"! LOL

[Vaughn MacKenzie]

I switched to synthetics just after 10,000 miles on my truck and have done 20,000 mile oil change intervals ever since.

I am coming up on 80,000 miles and so far so good. I change the stock filter every 7k (3 times per change) and send in an oil sample every 10,000 miles.

Every sample taken when I change my oil comes back looking great, very little wear metals, oxidation, TBN or viscosity depletion, and so on.

I've used Amsoil 15W40 and Delvac 1, both give awesome numbers. The Amsoil 5W30 didn't do so well though and I don't recomment it.

This is on my '01 Dodge Cummins running in the low-mid 300hp range but not much towing.

Vaughn

[chuntag95]

Vaughn,

What was the deal on the 5W-30? Was it the normal or the heavy duty diesel? Was considering it and would like your thoughts.

[HDLD]

Yes, I was considering the Amsoil HD 5W30 as well so would be interested to learn what concerns there are and why it didn't perform so well.

I've also read a few messages that mention performing an oil analysis but I don't understand how you can get valid samples unless performed during an oil change using a midstream sample?

[Vaughn MacKenzie]

Chris & HDLD, it wasn't that the oil performed poorly or anything like that, it's just that my numbers were not as good. The wear metal count after 10k was in the 50s whereas with the other oils it was in the upper 20s to low 30s (PPM). Other than that oxidation, TBN and the other factors were excellent. I was uncomfortable with it in my climate being it was as hot as 113F this summer, I felt it was a bit too thin.

The nice thing about the Delvac 1 is it has an incredibly low pour point like Amsoil 5W30 yet is as viscous at 100C as the 40-weight oil (thus the 5W40 rating). I am on my first change with this and at the 10K interval I had the best sample ever. I am looking forward to my 20K cycle.

There are other guys with the Cummins running 5W30 and have had good numbers. I think 5W30 is fine unless you live in the desert like I do.

Vaughn

[HDLD]

OK, Vaughn...that explains a few things. I guess I won't have the same problem in Canada. It would be interesting to see how the 2 compared. Does anyone know of any sources that do comparative testing in at least a semi-scientific manner? Is Amsoil prone to higher wear metal counts or is this simply related to it not being the best solution for very hot climates? Any difference in mpg? Does anyone have any oil analysis figures to support lower wear metal count numbers in a cooler climate with Amsoil HD 5W30? That was the "HD" 5W30 you were using, correct?

[chuntag95]

Vaughn,

Thanks for the additional info. I will see what the numbers are on the 15W-40 sample I just sent off to compare to yours. In Texas, we too get a bit toasty at times. :D Canada, brrrrrrrr :eek: It there was a Bahamas Tech, I would have got my degree there. :D