Using Mobil 1 Turbo Diesel Truck oil in gas cars.

[thastinger]

Most people use a diesel oil in a car engine because diesel oils usually have high levels of Zinc and P. But that particular oil doesn't seem like it would be good at either one as it has an SN rating, which means they have to reduce the levels of what makes diesel oil good IOT get the gas engine rating.
If the world ended, I would use Rotella 15-40 in everything.

 

[RooflessVW]

I wouldn't, and don't, use Diesel oil in a gasoline engine. They are formulated for an entirely different operating and contamination environment.

Actually, if the oil is dual rated then it's formulated for both.

 

[BMWTurboDzl]

Maybe I got this backwards but I think diesels would be harder on oil than gasoline powered cars given the operating conditions not to mention the high torque and horsepower. Even the highest horsepower gasoline powered engines don’t come close to the compression ratios of diesel engines.

Just my $0.02

Diesels operate at much lower rpms and the turbos run a couple of hundred degrees cooler than gasoline.

 

[BMWTurboDzl]

That's why I'm asking here and to set him straight.

If it's dual rated then no big deal. That being said with the introduction of ULSD over a decade ago the advantage of "extra additives" is no longer as great as it used to be. Besides, diesels operate at lower RPMS, and burn cooler than gasoline engines (Diesel turbos run cooler by a couple of hundred degrees F).

IMO people who use diesel oil in their track gassers think they're getting the same performance as race oil but a lot cheaper.

 

[atikovi]

Besides, diesels operate at lower RPMS, and burn cooler than gasoline engines (Diesel turbos run cooler by a couple of hundred degrees F).

But what about the argument that compression ratios are much higher and diesels introduce much more contaminants into the oil, so diesel oils must be more durable than gas oils?

 

[BMWTurboDzl]

But what about the argument that compression ratios are much higher and diesels introduce much more contaminants into the oil, so diesel oils must be more durable than gas oils?

Soot loading is an issue for sure but I'm not aware of how that would be relevant in a gasser on the track. As I said with ULSD I don't think the TBN of diesel oils is that much greater than gassers let alone a race oil. It's cheap though which has always been the big draw.

What is the TBN of modern HDEO?

EDIT: TBN isn't much different. Min TBN of E7 vs A3/B4 is 9 and 8 respectively.

 

[Bud_One]

I used store brand 15W-40 in my old Accord to top it off when it's low.
I rev it daily to 6k rpm ... no issues in my use. YMMV though..

 

[simple_gifts]

Except it's a 5W40.

I was addressing the quoted comment "I don't know how people can put diesel oil in their Elises" and the shear stability concern expressed.

 

[BigTimeTA]

The only catch about using HDEO in a gasoline engine is that it tends to use primary ZDDP which needs higher temperature/pressure for activation. However, I think this might apply in case the oil was Cx only and wasn't not made with Sx in mind during formulation. Just a speculation.

 

[ctrcbob]

Sixty years ago (yes, I’m old) I used to use Shell Rotella-T in my 1962 Buick. Never had problems.

 

[cheesepuffs2]

Regarding high RPM usage, it's not about sheer stability. It's about the lesser amount of defoamer in an HDEO versus what is formulated (for good reason) into a PCMO.

There's no magic to diesel oil that makes it the best choice for diesel engines, and gasoline car engines, and shared sump motorcycle powertrains. There products are all different categories and formulated with different engine living conditions in mind because they are just that - different conditions. If diesel oil was superior for all situations, then there wouldn't be PCMOs and HDEOs and motorcycle oils. There would just be simply motor oil, one category.

Remember that formulations are all a delicate balance of components. These components can offer both pros and cons, and the end result is the "best" solution for the intended use. It's all a blend of compromises.

 

[Mainia]

Soot loading is an issue for sure but I'm not aware of how that would be relevant in a gasser on the track. As I said with ULSD I don't think the TBN of diesel oils is that much greater than gassers let alone a race oil. It's cheap though which has always been the big draw.

What is the TBN of modern HDEO?

EDIT: TBN isn't much different. Min TBN of E7 vs A3/B4 is 9 and 8 respectively.

GDI soot. It is measurable in UOA.

 

[BMWTurboDzl]

GDI soot. It is measurable in UOA.

I'm aware but is it relevant in a race environment? I'm going to say not a chance. The only reason why people used it back in the early 2000's. was because it was considered a poor mans race oil being that diesel fuel was substantially higher in sulphur (Which hasn't been the case for over a decade).

1 Gallon of T6 ~$25 or $6.25/quart

Quart Price of race oils:

Redline 15w40 Race oil $20
Redline 5w-30/40 HP $16
Motul 300V ~$40 or $20/Liter
Valvoline VR1 $8
Mobil 1 0w40 $11
Mobil 1 5w50 $11

 

[ammolab]

But what about the argument that compression ratios are much higher and diesels introduce much more contaminants into the oil, so diesel oils must be more durable than gas oils?

So the diesel oils are great for high bearing loads and plenty of dirt? Good!

How does that make them BAD for the lesser loads and dirt found in gas powered engines?

That’s like saying we built this bridge for MAX loaded 18 wheelers ….so it may not be suitable for Vespas!

 

[k1xv]

For the longest time I used Rotella T6 in everything. Many bikers use it in air cooled motorcycles.

 

[Cujet]

there are modern automotive and light truck diesel engines that have higher redlines than you might expect. 5000 is not unusual, the same as my 5.4L Ford gas engine

 

[cheesepuffs2]

there are modern automotive and light truck diesel engines that have higher redlines than you might expect. 5000 is not unusual, the same as my 5.4L Ford gas engine

There are bikes that redline to 16,000 RPM off the showroom floor.

Personally, I'm not using an oil that's only formulated to control foaming at 5,000 RPM in that case.

 

[twX]

Diesel engine oil has been popular in motorcycle communities for decades. Shell Rotella T in particular, since it has a JASO MA2 certification for wet clutches. The synthetic T6 5W40 does tend to shear quite a bit in high-revving motorcycle engines. The conventional Rotella T4 15W40 is quite shear stable.

There are some diesel engine oils with an API SN rating, like Mobil Delvac, meant to be used in fleets with both gasoline and diesel engines. These oils will have lower phosphorus than dedicated diesel engine oils, but usually just under the maximum allowable level for the API SN rating.

As for motorcycles, the multi-use gasoline/diesel oils may be suitable for motorcycle wet clutches in practice, but they will never have the JASO MA2 rating, since the required phosphorus level for JASO MA2 is incompatible (higher) than it is for API SN. I've used Delvac 1300 Super and Rotella T4 in my bikes without any issues.

 

[cheesepuffs2]

What makes T6 less shear stable than the lower-tier T4?

 

[twX]

What makes T6 less shear stable than the lower-tier T4?

It's probably because the T6 has a wider grade range (5W40 for T6 vs 15W40 for T4), so more viscosity modifiers, and a larger reduction in viscosity when they break down. You might expect that the full synthetic would still hold up as well or better than the conventional, but this doesn't seem to be the case with Rotella, based on the UOAs that I've seen.