anyone use mobil 1 5w40 in their diesel yet. i am thinking of trying it since i use mobil 1 in my gassers i would think mobil 1 with a diesel rating of ci-4 would be great also.

 

If I were going to use a Mobil synthetic, their Delvac 1 is specifically formulated for diesel applications. Reportedly, it is also available in a repackaged "Truck and SUV" synthetic formulation.

Rusty

 

true but its not mobil 1, mobil 1 5w40 is a fully diesel rated oil for all temps unlike delvac 1

 

The following is from Mobil's website:
Seems pretty straightforward to me.

Rusty

 

This is also from the Mobil 1 site, in reference to the Truck & SUV Formula:


Fully synthetic Mobil 1 Truck & SUV Formula is engineered for some of the hardest-working vehicles on the road today. Whether hauling or towing heavy loads, driving off-road or just dealing with stop-and-go driving, Mobil 1 Truck & SUV Formula provides outstanding protection for gasoline and diesel engines. It has been proven in some of the most extreme, heavy-duty performance testing.
Benefits of Mobil 1 Truck & SUV Formula 5W-40:*

* Helps protect hard-working engines in high temperatures and delivers outstanding cold-start protection.
* Has exceptional resistance to low-temperature sludge build-up and high-temperature varnish deposits to help keep engines running clean and long.
* Has outstanding wear protection to help extend the life of critical wear surfaces.
* Meets and exceeds the most stringent U.S., European and Japanese industry and engine-builder specifications and approvals, including:

- API SL/SJ for gasoline engines.
* - API CI-4/CH-4/CG-4/CF-4/CF for diesel engines. Meets diesel engine requirements of Cummins, Powerstroke, Duramax and Navistar where API CI-4 is required.

Applications:
Mobil 1 Truck & SUV Formula 5W-40 is ideal for hard-working pickups, vans, sport utilities and other light- and medium-duty trucks, whether diesel or gasoline powered.

* Follow the viscosity grade and API service category recommendations in your vehicle owner's manual.


Kind of confusing. They seem to be giving conflicting advice.

 

actually i just spoke with one of mobils tech lines and he told me that delvac 1 and mobil 1 5w40 are exactly the same product. i asked why are they in different packaging then and he told me that it is a marketing issue. they both are exactly the same grade 5w40 and both have a ci-4 rating. i am buying my 11 quarts today

 

Well, it's your truck so you may dump in whatever you like. But if it doesn't say API CI-4 on the bottle (which Mobil 1 doesn't), I wouldn't use it. Now, "Mobil 1 Truck and SUV" is CI-4, but so far I've only found it in quart bottles. HOWEVER, if your truck is an older year, it is very possible it could use an older API rating such as CF. Then Mobil 1 is acceptable.

[edit] Mobil1 isn't available in a 5W40 formula. You must be referring Mobil 1 Truck and SUV formula.

 

I think we are getting confused over two different product lines... the standard Mobil1 line intended for automobiles which is not recommended for heavy duty diesel service and the Mobil1 'Truck and SUV' product which according to Mobil is intended for heavy duty diesel (CH-4/CI-4) applications.

 

As the viscosity range of a multivis oil increases there is more of a tendency for the upper viscosity to drop rapidly. Thus your 5w-40 oil becomes 5w-30 in a short time. No problem for the winter but I personally wouldn't use an oil with such a large viscosity range for hot weather.
This applies to all oils, synthetic and dino.

 

While it's true that oils with a high viscosity range use more viscosity improver compounds and can degrade more rapidly than a narrower-range oil, synthetic oils are much more robust in this regard and I don't think you can make a generalization that all wide-range oils are less desirable than narrower-range oils. It is quite possible that a good synthetic oil with a 5W-40 range may in fact hold up better than a regular oil in a 15W-40 range. The only way to know for sure would be to test.

That said, I'm not sure why anyone would use synthetic oil in a diesel engine unless you were expecting to operate in very low temperatures, not because of the viscosity range of the oil but just due to economics... not much bang for the buck there unless you are operating in a condition that really requires a synthetic.

 

mobil 1 5w40 is yes the truck and suv formula. i just think if i run it in all my gassers all the way to my motorcycles and does a superb job of keeping the engine clean and my trannies clean then i should use it in my cummins.

 

This is not true of a quality synthetic like Delvac 1. A good synthetic base stock does not require large amounts of viscosity index improvers (VII) to stay in grade over a wide temperature range because the viscisity is more stable than dino oil. VIIs are polymers that change shape on a molecular level with temperature, so they are thick when hot and thin when cold. But, polymer basically = plastic.

Dino oils and cheapo group 3 synthetics like Rotella do need a lot of VII's to perform as advertised and have the problems you describe. Also, more VII's in an oil mean less oil in the oil and more plastic.

 

DINO OIL ROCKS!!!!

 

Valvoline Premium Blue comes in a synthetic formula also. When I bought my oil and filters at a Cummins shop the guy said most people don't need the synthetic. Very few of their customers used the synthetic version. It also happens to be about double the price of dino oil. This was in North Dakota where the winters tend to be a little on the cool side.

Page 328 of the owners manual states
"NOTE: The same oil change interval is to be followed for synthetic oil as for petroleum based oil. Also, synthetic oil must meet the same performatnce specifications as petroleum oil."

It then shows a scale with 15W-40 viscosity grade and show 5W-40 Synthetic with the advantage of the synthetic for the lower temps.

My understanding is that there is only so much material that can be kept in suspension and that is the reason for the same change interval recommendation.

 

Even though the book says that you should change oil the same with dino as synthetic, the intervals that the book recommeds is alot more then you think. I am not sure what it says for you truck, but I think that mine is atleast 8K. There are also many people that run oil tests on their oil and run them up to and over 15k. If you are running that long though it is a good idea to change the filter inbetween. It is just a matter of choice I guess.
Dave