WHAT OIL TO USE

[polaris800]

I have read a lot about people using many different kinds of oil in the duramax. Which oil is better for the engines in the long run? Rotella/mobile/amsoil etc....... I feel that if your oil meets all the specs for the engine then you should not have a problem in the long run. Has anyone ever seen a true test done using the synthetic olis on this engine. I mean to the point of actually test two engines under the same conditions then breaking the engines down and spec testing all the parts that would normally wear do to there use. I know all the bull that the oil manufactors will tell you but has this ever been proven to out work the regular oils grades if you are changing your oil under normal timelines. Just was wondering.

[FightinTXag]

I don't know if anybody has run the kind of extensive testing that you are talking about with the duramax. I was convinced to use synthetic (Delvac 1) after someone posted about turbo life being a lot longer for heavy-duty engines when using synthetic. EGT's can reach 1200 in these motors so the oil in the turbo can bake if you shut them down hot. You can monitor your pyrometer to make sure EGT's have cooled before shutting down, but that doesn't tell you the temperature of the turbo itself. I'd rather use synthetic which I know can handle the high temps without breaking down and forget about it.

[MudNurI]

we use Delvac- synthetic as well. Nobody has proven to me that I NEED to, however after shelling out $45K's for the ride, it's the least I can do..same thing with the filters- some people can justify saving $7 and buying them at Wally-world- I for one can't, and will continue to run the GM filter.

oh- and our dealer changes our oil as well- nobody's going to tell me that it was lack of required maitenence that messed up my truck in the future!

Brandy

[ChopperBill]

Just had my first oil change at the dealer and they put in Delvac 1300. Wanted to get a couple of quarts to take along for our vaction. The dealer only had it in bulk(kind of thought that was crap). Went to 6 auto and discount stores. NO DELVAC! Finally had to go to an oil distributor and by a whole case. Have no idea if I was on the road and had to find a quart or two. Shell Rotela was available at just every place I checked. Sort of wished I went that route.

[LanduytG]

Use the Amsoil 15W-40 Heavy Duty Diesel and Marine. Its only 3.45 a quart if you buy it in a 5 gallon case(2-2 1/2 gallon jugs)plus a top quality filter for 8.70. All you have to do is pick up the phone then wait for the brown truck to drop it off. You don't have to go looking all over to find what you want that way.
Greg

[ChopperBill]

Will that little brown truck find me on the road when I'm 1000 miles from home? ;)

[mowser]

FightinTXag:
I don't know or not if you are aware that the Duramax has a "Turbo" that is cooled by both coolant and oil. So therefore cooling the EGT's down to 300 degrees F isn't that critical. I also own a 1987 SAAB 9000 "Turbo", the "Turbo" has the same idea as my 2002 Duramax, it's got both liquid and oil cooling, and the manual states that after high speed driving (autobahn like speeds) to idle the engine for "20 seconds" before shutting off the engine.
This isn't the case for the Ford or Dodge "Turbos" unless they've changed for "03", so therefore I'd bring them down to 300 degrees F before I'd shut them down. :D

mowser

[motovet]

What Greg said.

[mdrag]

mowser,

...but the oil and water circulation STOP when you turn off the engine - heat soaking of the oil supply lines or turbo bearing can occur - leading to varnish build up and coking (carbon build up) in these areas - ultimately leading to oil starvation and turbo failure. I remember reading that this is one of the major causes for TC failures.

Synthethic oils tolerate the TC's high heat stress much better than conventional dino oils, with little if any coking. IMHO, I would only use a good synthetic oil in any TC application.

There are only a handful of production engines that continue to circulate coolant through the turbo after the engine is shut down - Audi and Porsche had this feature on some of their engines.

[hoot]

mdrag,

There is a cavity filled with cooling water surrounding the turbo bearing. When the engine is shut down, that water doesn't go away. Coking of oil in our turbochargers is highly unlikely no matter what you do. As a matter of fact, turbochargers today are quite reliable even without water cooling.

[FightinTXag]

"There is a cavity filled with cooling water surrounding the turbo bearing. When the engine is shut down, that water doesn't go away."

It doesn't go away, but it's not circulating. How much heat can a pool of water dissipate when it's in the middle of a hot body? Not much compared to when the water is circulating and carrying away heat. All it can do is absorb heat until it reaches the same temperature as the surroundings.

The oil and water stop cooling the turbo as soon as the engine is shut down because circulation stops. The temp of the turbo at shutdown is what temp the oil (and water) trapped in the turbo will be exposed to for a long period of time instead of the relatively short time when circulating through during operation. How hot is the turbo? I have no idea, but I'm willing to bet that it's warmer than the oil pan or engine.

That's why I'll use the synthetic. Even if it doesn't significantly extend the life of the turbo, I believe the synthetic will hold up better when exposed to these higher temperatures for long periods and thus provide better protection for the entire engine.

[ 10-01-2002: Message edited by: FightinTXag ]</p>

[mdrag]

hoot,

Here's a quote from a post by George Morrison:

QUOTE
================================================== ================================================== ===================

"...Plus one very important point. In the 20 years they have been running Mobil Delvac 1 they have *never* lost a turbo. When I visit other trucking companies generally the first thing I have to step over when walking in the door is a skid of failed turbo chargers. Mineral base oils coke in super hot turbo charger bearings causing heat build-up and either the case cracks from heat or the bearing seizes. Synthetic oils simply do not coke, thus eliminating the #1 cause of turbocharger failures. Many times these failures take downstream components with it..."

================================================== ================================================== =====================

http://forum.62-65-dieselpage.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=3&t=003391&p=

Although George is not specifically describing TC failures in Dmax engines, what makes our TC so special that this becomes a non-issue? Must be the 'wimpy' or poorly designed TC's used in those commercial engines ;)

George forgot more about oil in 1 day than I'll ever know... :D When more Dmax engines reach 200K + miles we'll know for sure, but in the mean time - I'm sticking with synthetic oil. My 02.

mdrag

[hoot]

Yes mdrag, they used to have more failures than they do today. His info quite often is "legacy" ;) info. Todays turbos are designed with more modern materials and technology. You don't see much talk on the Ford and Dodge forums about failed turbos and theirs aren't water cooled.

Also, there was no mention of water cooled turbo in the quote.

Get a paper cup. Fill it with water. Light up a propane torch and put the flame directly on the side of the water filled paper cup. The paper will not burn and the water inside will begin to convect. That is what happens when you shut down the Dmax. The water that is still in the turbo housing will get hot and convect, creating a localized circulation.

All I'm saying is the water cooled turbo makes a huge difference when compared to a non-water cooled turbo in reducing temperature after shutdown.

I'm not disputing that certain oils may add life or cooling the turbo before shutdown is good to do. Both things may add life to the turbo.

[ 10-01-2002: Message edited by: hoot ]</p>

[FightinTXag]

Hoot,
In your paper cup example, the water is carrying heat from the hot cup side and releasing it to the air above. A percentage of the water is also evaporating and that change of state is absorbing a large amount of heat energy. In a closed, pressurized system, like the cooling system, the water cannot reject heat to the atmosphere and evaporation will not occur.

Therefore, the only means the stagnant cooling water has to absorb heat from the turbo is by it's temperature rising to that of the turbo. There is no cool side for the water to eddy and reject heat to.

[sw11497]

Factory uses Delvac 1300S. You can usually get the same oil at Wal-Mart for around $6/gallon. Try the filter from gmpartsdirect.com. Same black filter the factory installs.

[LanduytG]

I guess I need to clear up what I said above. If you are stuck on using a 40 weight oil then the Amsoil 15W-40 Heavy Duty Diesel and Marine is much cheaper than Delvac 1. But if you are open minded and can except the fact that a 30 weight can still protect as well as a 40 weight then use the Amsoil Series 3000 5W-30. I had a couple of emails and phone calls about this today thinking that I recommended the 15W-40, not true I will still make my first choice the 5W-30.
Greg

[GMCTRUCK]

My partner's 97 PSD has 140k miles on it. For the most part he has used dealer filters and Napa 15-40 oil and changes his oil at 5k intervals or when I remind him. The engine has not had any mechanical problems (tons of electical glitches though, thing eats cam sensor like candy) My mostly retired (plow truck only now) 91 GMC has 240k miles on flavor of the month oil and stock filters. On my new truck I changed the oil at 500 miles with Rotella and will probably use it from now on but, is "fancy" oil really worth it?

[chuntag95]

Insurance. That is why I use synthetics. I have a '70 Pontiac that the thermostat stuck closed in August in Texas. Cooked every gasket in the motor and it stopped running. :eek: The idiot light never came on :mad: (but it was 22 years old). Flashed water out of the radiator for over 45 minutes. I was running Mobil 1 at the time. After it cooled, I replaced the thermostat, changed the oil and replaced gaskets like crazy. That was over 65,000 miles ago and it still doesn't burn any oil. :D On the other hand, my father-in-law has an 82 GMC with 340,000+ miles and has only run Delo in it. He changes it religiously and has never had the engine open. He does drive like Grandma on Sunday ;) I figured up how much I spend extra to go with synthetic and I am still WAY ahead by saving one motor. :cool: Since I change it myself, it really doesn't cost me any more than if I took it to the quicky lube. I bought a single quart to keep in the truck, but have never needed it. Just by gallons now. To each his or her own, but I will take any insurance I can get, especially when it's this cheap. :D :D