I still dont get the Diesel oils

Messages
450
Location
Louisville, KY
Arent they missing the friction modifiers we need in Gas engines? And the extra detergent is nice but it has got to be displacing other equally important components in the formulation right? On ym home site I have a retired oil formulation chemist who tells me diesle oils are not a good choice in gas engiens for this reason Someone please clear this up for me? Fred... [I dont know]
 
Messages
5,117
Location
Airlie Beach Australia
Hi, palmerwmd - you are correct, pure diesel oils should NOT be used in petrol engines The HDEOs that have joint API ratings such as C?/S? CAN be used with confidence if the S? rating is as required my the engine manufacturer. The same applies to the ACEA ratings. Regards
 
Messages
1,715
Location
Texas & BWI Area
Chevron Delo 400 and Mobil Delvac 1300 specifically have API SJ/SL for gasoline engines. Nothing more to get. The "iffy" one is Redline 15W40 and the phosphorous issue.
 
Messages
11,247
Location
PA
Some specialty oils have manufacturers' specs that cover both diesel and gasoline engines. For instance, the Belgium Syntec 5w-40 has the VW 502 gasoline as well as VW 505 diesel TDI spec, API specs too.(so does GC) Another example is Mobil 1 0w-40 which covers the same VW specs as well as various Mercedes gasoline specs which may also cover their "D" cars. (MB 229.X 228.3)
 
Messages
1,050
Location
Calif.
Those diesel oils like Shell Rotella, Chevron Delo 400 and Castrol RX Heavy Duty carry the dual rating API Service CI 4/SL. It should be okay to use in a gas engine as long as the owners manual doesn't say avoid using a dual rated or only use SL. But i'm not 100% sure.
 
Messages
548
Location
Texas
outrun- Redline 15W40 is the only one I've seen that specifically states "Diesel Only". It does not have the dual rating.
 
Messages
232
Location
Franklin, OH
The thread was posted in question about diesel oils not having FMs in them. The responses have ignored this for the most part. Most diesel oils do not have FMs, including Rotella T Synthetic 5w-40. To not use an oil with FMs is to remove a level of protection from your lubrication. They may meet "specifications" but that does not mean that it is in the best interest of your engine to use them. With an oil using FMs, there is a level of protection between the oil film and anti-wear additives in a high load condition. These diesel oils do not have that, period. Why do we recommend them here? Just to say that "it works in my car" or that "it still looks like honey" proves nothing. If anything it should darken quicker than non-diesel oils since it has more detergents. I think this is another one of those "group think" mentalities on this forum. It's popular to use diesel oils for some reason and I don't think it's backed up by scientific facts.
 
Messages
211
Location
Rome, Ga
blsnelling, Why would one kind of internal combustion engine require the FM's, while another would self destruct without it. They both have pistons, valves,etc. I am not disputing your claim , I just don't understand the logic. GregH
 
Messages
3,334
Location
Bolivia
If an oil is rated CI-4 and SL by the API, I think there is little we can say to dispute it. I have dozen, if not hundreds, of oil analisis that demonstrate <10 ppm of iron and <2 ppm of other wear metals in 7,000 to 25,000 kms of severe use. Can a non-CI-4 oil do as well because of a mysterious FM? I doubt that it matters, since those wear levels willl take the engine well over 500,000 km. There are a lot of old wives' tales out there. A lot of mechanics that can't accept new ideas. One engineer insisted that he could not use oil rated for both diesel and gasoline because they would only work in engines that ran a mixture of gasoline and diesel. That he learned that in Germany where he studied. Under API rules you can take a CI-4/SL oil and label it as CI-4, so I sent him some with a new label as a CI-4 and he has been a happy camper ever since. Results are what matters.
 
Messages
11,247
Location
PA
quote:
that does not mean that it is in the best interest of your engine to use them
Well, I guess the Audi engine factory goofed when they used GC/SLX as the original-fill in their 1.8t petrol, it meets TDI VW 505 specs too. [I dont know]
 
Messages
47,953
Location
Everson WA - Pacific NW USA
To say all SL rated "diesel oils" do not have FM's is WAY oversimplifying..... Bottom line: While I certainly wouldn't put a diesel oil in a new car, Honda, Ford or otherwise (because typically the viscosity is a bit high in say a 15W-40) - I would not hesitate to use one in a gasoline engine of any variety that had some miles on it. UOA's in my turbo, many other cars, and some quite extended UOA's with these diesel oils that are gas engine rated tells me there is ZERO harm done....
 
Messages
9,427
Location
Pensacola & Vero Beach FL
quote:
Originally posted by GregH: blsnelling, Why would one kind of internal combustion engine require the FM's, while another would self destruct without it. They both have pistons, valves,etc. I am not disputing your claim , I just don't understand the logic. GregH
Greg: I'm not endorsing the validity of bls's post, but with all due respect, your challenge is, ironically, illogical too. There are plenty of substantial differences between IC engines which can account for one needing some protective element whereas another might not. Sure, normal gasoline and diesel engines are structurally almost the same (pistons, valves, air intakes, manifolds, etc.). By the implied premise of your statement, you could fuel the diesel with gasoline and vice versa, which would likely be a disaster in both cases. So I'd say that structural similarity does not answer this question. In addition, I can envision a number of factors that might account for the FM non-FM distinction. I remember many years ago (I drove diesel powered busses for a living in college) a bus mechanic explaining to me that just the rings alone in a diesel were sufficiently different from those in a gas engine that the engine required different lubrication. Maybe it's that. Maybe it's the typically lower RPM ranges at which a diesel operates. Could be a number of things, or a combo of several. My point is that there are plainly enough variables present to account for the FM (and other) difference between the two oils. Perhaps one of the petro engineers can shed some more specific light on this.
 
Messages
7,788
Location
Oklahoma
But if it's rated SL, then FM or not, it is just as good as those with it. So, like what's the point? The VOA's and UOA's have proven that this is a good oil on both types of engines.
 
Messages
8,937
Location
SC
quote:
Originally posted by blsnelling: With an oil using FMs, there is a level of protection between the oil film and anti-wear additives in a high load condition. These diesel oils do not have that, period.
This is simply incorrect. Friction modifiers in PCMOs are there to promote improved fuel economy. Under EP conditions, they do little or nothing in the way of preventing wear. That's where the ZDDP, overbase calcium, boron, and moly work synergistically to prevent wear. (Moly at the level found in most oils acts by itself as a FM, but in conjunction with the other additives it performs AW/EP duty as well.)
 
Messages
13,132
Location
By Detroit
I think the major difference between diesel and gasoline engines is the much higher compression in a diesel, which would require a more robust oil (probably will never see a 5w20 diesel oil), and the dirtiness of the fuel in a diesel, which requires much more detergents and additives to soak up the filth. Maybe the FMs are not present because they would interfere with other, more important additives such as higher levels of dispersants to keep the soot particles from clumping and clogging the engine. As for the rings being different, that goes back in part to my first point, that diesels have much higher compression. When an oil is rated both gasoline and diesel, there may be some compromise. Perhaps lower additive levels than a diesel only oil so the plugs on the gasoline engine don't foul from additive overload. But then regular PCEOs are compromised by the CAFE-induced starburst energy conserving standard. So, on balance, I think the closest thing to an ideal PCEO is any PCEO of 10w40 or higher (as these do not have the starburst/energy conserving stuff) or the so-called "high mileage" oils because (I believe) none of these has the starburst/energy conserving rating.
 
Messages
13,132
Location
By Detroit
quote:
Originally posted by blsnelling: I took that to mean there was a level of protection missing rather than a level of CF which affects mileage.
That was my initial reaction. I had to make a hard copy of MolaKule's post and digest it overnight before I began to suspect that wear was not the issue.
 

TC

Messages
1,644
Location
California
FROM VARIOUS VOA'S: Havoline 10w-30 SL (Gas) Zinc: 822 ppm Moly: 43 Phos: 654 Formula Shell 10w-30 SL (Gas) Zinc: 857 Moly: 1 Phos: 731 Citgo Supergard 10w-30 SL (Gas) Zinc: 1,165 Moly: 95 Phos: 1,196 Mobil Delvac 1300 Super 15W-40 SL (Gas/Diesel) Zinc: 1,231 Moly: 35 Phos: 1,120 Chevron Delo 400 15w-40 SL (Gas/Diesel) Zinc: 1,376 Moly: 0 Phos: 1,116 Mystik (Citgo) JT-8 Super HD 10w-30 SL (Gas/Diesel) Zinc: 1,632 Moly: ? Phos: 1,590 John Deere Plus 50 0w-40 SL (Gas/Diesel) Zinc: 1,744 Moly: 121 Phos: 1,906 PLUS TWO OLDER "SJ" DUAL-USE OILS: Pennzoil Long Life 15w-40 SJ (Gas/Diesel) Zinc: 1,651 Moly: 153 Phos: 1,707 Shell Rotella 15w-40 SJ (Gas/Diesel) Zinc: 1,587 Moly: 0 Phos: 1,654 I'll let others properly decipher this.
 
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