Hi guys! Just need some ideas. I was goin to change oil in my '02 and found when I went to get the oil from my shop i was one quart short to change. I use the mobil 1 truck& suv 5w40. Can i use a quart of mobil 1 5w30 that is for both gas and diesel? If i need the 5w40 ill have to wait a while cause i get it at wally world and its 130 miles round trip for me to get it.

 

I'm by no means an expert, but I'd say it's ok. I know people who use Mobil 1 5- 30 in their diesels. They buy it at Costco, cheaper. I don't think it would hurt a thing. Just my 02 cents.

Gary

 

I would not blend the oils. The basestock & additive packages are different.
I assume going synthetic means you will go extended drain?
Delvac 1 would be a much better choice if you can find it. I keep a gallon jug on my front porch if you can find me......

 

That will be safe to top up with 5w-30, as both are same brand and near same warm weather rating, and both synthetic without any worries.

It use to be not recommended to mix coventional/synthetic or even different brands, but technology has improved so now they are all compatible, you won't even notice it.

I also run Mobil 1 synthetic 10w30 every year all thru winter.

 

Regular Mobil I (not the Truck and SUV, which is rebranded Delvac I) is not intended for modern heavy duty diesels as it only carries an API CF duty service rating. What does your truck require? Check your owner's manual.

Rusty

 

Depends what you classify as modern. CF-4 and CG-4 are THE rated oils for 2nd generation trucks. CG-4 CH-4 CI-4 are THE rated oils for 3rd generation trucks.

If oil is rated CF-4( "C" denotes compression engine=DIESEL) on it or higher it will work also in all previous generation engines(light, medium and heavy duty applications with minimum CF-4 rating). If it carries this rating don't worry about it, and put it in.

 

No, if your truck requires something higher than a CF-rated oil, then the regular Mobil I doesn't meet the service classification rating. That's why I suggested that one check the owner's manual before deciding if it's OK or not.

At least at my local stores, the Mobil I Truck and SUV 5W-40 is on the same shelf. If one wants to use a Mobil I synthetic in one's diesel truck, why not buy the right oil - those being Mobil I Truck and SUV or Mobil Delvac I?

Yes the C=compression and S=spark is an easy way to remember the service classification, but it was originally designated as C=commercial and S=service (retail).

Rusty

 

If it's only 1 qt. you're short, why not just fill up with what you have, and then add the single qt. later?

 

Yup! I agree with Rusty!
Still listed this way, by Lubrizol anyway...C=Commercial, S=Service. Commercial rating, from the outset, was clearly understood to mean Diesel.

No only would I not use an oil rated below what my book called for....I would say, why not use only CI-4 oil (the lastest) .... the major difference is lower soot buildup....which I think, even all members here would agree, is a good thing.
The lattest classification of Diesel oil may not always be better for your truck...but in this case, I believe it is.

Mixing brands and/or weights is absolutely OK. When mixing weights, be sure you understand what weight you are ending up with. Mixing synthetics & mineral based oils is OK also....that's all a blended synthetic is anyway.

RJ

 

Check his signature, he has '02 truck, which manual calls for CF-4 or CG-4 rated oil. As I stated, IF IT HAS that classification rating on jug/bottle of oil it is perfectly safe to use, doesn't matter where you buy it at.

As far as "original classification" "C" commercial, "S" service goes those are irrelevant to current classification of oil today and has been for many many years. "C" today stands for compression=DIESEL, "S" today stands for spark ignition=gasoline. If oil is rated as a CF-4 or higher it IS ENTIRELY SAFE to use it in an engine specifically rated for CF-4 oil. Not looking for war, just stating facts. Nuff said.

 

If it were me I would just run it a quart low. I don't think one quart would make any difference if you decided to add it as both are the same basic oil and formula. The only difference would be the extra additive to bring it up to the more stringent standard. No worries either way imho.

 

I always cringe when i see a thread about synthetic oil. Not because i don't believe in them...but because many people fall for myths and don't use the oil properly. Synthetics are great for certain reasons: Better lubrication, less wear, much better cold starts. But some people fall for the 25,000 miles between oil changes myth. Well it doesn't matter what you have for oil...synthetic or dino...oil gets dirty. Not only because of wear to the engine...if that was the case, and oil got dirty enough from wear in 3000-5000 miles to require changing, then your engine would be worn out by 50,000 miles. Most of the "dirt" that oil picks up is from the combustion process, and gets past the rings. I have seen Mobile-1 at 20,000 miles, and it comes out of the drain plug like old gear oil. Very thick and black. Thats not just 1 experience...I've seen it over and over by people who think they can go 20,000+ miles.

So in my opinion, running synthetic is a good thing...just make sure you change it regularly. Maybe not 3,000 miles, but keep an eye on it and change it when it gets dirty. Get used to what clean oil looks, smells, and feel like between your fingers. When you check your oil, smell it, look at it, and touch it.

I know this is a bit off the topic of the original post, i just wanted to jump in where the "synthetic guys" are hanging out.

Jim

 

Good point to bring up about changing oil regularily. The use of synthetics does not mean you can drive excess miles between changes. Additive package breaks down in syn too, and only sure way to tell when to change is by oil sampling. This is not practical for most people though.

I still think you can extend oil change longer with synthetics, just not doubling it. As a rule of thumb, I have found 7000-10,000 mile interval depending on many variables, is average range to c/o oil and filter. I have backed this up with oil sampling(free at work) on my truck and previous trucks. This will vary though by how much stop and go driving, excess idling or cold idling, getting engine up to operating temp, temperature extremes, loads, etc. placed on truck.

 

On the note of changing oil often. I have a friend who rides a 1998 WR400 Yamaha dirt bike on the street.....a lot. No telling how many miles/hours. He uses cheap oil and changes it often. So what this says is there is something to the thinking on changing oil often.

 

What does he do to determine when to change it then, if he doesn't go by mileage, or hours? Big difference in the two units, you can't even compare them. Using cheap oil in a dirt bike is one thing, using cheap oil in a Cummins, even for a short time is asking for trouble. Doesn't make economic or ecological sense either to change oil way too early for any rig, but then a bike only holds a couple of quarts.
Best advice, follow the regular or severe duty service schedule depending on your driving style for the Cummins. Dirtbikes- your call.