diesel oil in a gas engine?

[iskerbibel]

Ok, I've run Case(construction equipment) 15W40 engine oil in my truck for a few years, with no apparent problems. I've quite recently switched to John Deere 15W40 plus 50 in both my truck and my wife's car- mainly because I've started working at a john deere dealership and get leftovers for free. My question is: Is there a significant difference between oil designed for gasoline engines as opposed to oil designed for diesel engines? If so, what's the difference? Am I dooming my ford 300 I-6 and my wife's 3.1L V-6 to an early grave?

A feller I worked with at case told me once that he thought the "ash content" was the main difference, and that running diesel oil in a gas engine isn't good. Obviously, I didn't put too much stock in that... anybody know for sure?

 

[Steve S]

The company I used to work for used Delo 400 in all their ford vans I stopped working for them in 2000 "even the new vans" in the 17 years I worked there there was never any engine problems . The vans would fall apart with good running engines . The vans were not pampered. What is the plus oil like and how does it perform?

[ August 25, 2003, 11:27 PM: Message edited by: Steve S ]

 

[Ken2]

John Deere Plus-50™ 15W-40 Engine Oil carries an API Service Category SL rating, so it's OK for gasoline engines...if the 40 wt. viscosity is OK. You have your location secret, so we'll keep a secret from you about whether or not you should keep using this oil.


Ken

 

[Chris 2421]

I'm using 15w40 in all of my street vehicles and it's worked well.

 

[moribundman]

I would like to know if the lack of friction modifiers in oil for diesel engines causes increased wear compared to oil for gas engines.

 

[moribundman]

Does this mean reduced friction does not necessarily result in reduced engine wear?

 

[Sin City]

15W-40 should work great in the old Ford 300 CI motor. As far as the 3.1L GM engine I think an API SL/CI-4 15W-40 motor oil will work OK in a warm climate. If you live in a cold area or the 3.1L motor is fairly new then you would be much better off with something thinner like 5W-30, 10W-30 or 10W-40 API SL motor oil.

Diesel oils usally have a greater amount of additives and will also have a higher ash content. The greater amount of detergents will help to keep the motor clean but the higher ash content can also lead to increase deposits in the combustion chamber.

[ August 26, 2003, 05:42 PM: Message edited by: Sin City ]

 

[MolaKule]

Friction Reduction additives mostly reduce viscous friction (in the oil) and light boundary contact.

Anti-wear and Extreme Pressure additives are really the wear reduction additives.

As to how they function and the definition of each type of wear, see:

http://theoildrop.server101.com/ubb/ultimatebb.php?ubb=get_topic;f=4;t=000089#000000

[ August 26, 2003, 05:41 PM: Message edited by: MolaKule ]

 

[moribundman]

Thank you MolaKule, this answered my question more than I had hoped for.

 

[Jimbo]

The FM's in GF-3 oils are not anti-wear agents. They are there for the "energy conserving" part of GF-3. AW additives, especially ZDDP, do the anti-wear duty. Look at the UOA's. Mine show extremely low wear metals with Delo 400 in a gasoline engine.

 

[MolaKule]

iskerbibel,

Diesel oils have more ash-type (metallic based) detergents/dispersants and higher levels of ash-type (metallic based) AW/EP adds, so yes the ash content and deposits would be higher in a gasoline powered engine where the combustion temps are lower than in diesel engines.

However, using combustion cleaners occasionally, such as Neutra, Fuel Power, etc, should keep the gasoline combustion chambers, plugs, and valve stems fairly clean.

 

[Jimbo]

Combustion temps higer in diesels? Exhaust Gas Temperature readings with gasoline engines are normally higher as are Tubine Inlet Temperatures for tubochargers with gasoline engines. Diesels normally run an excess of air, while gas engines run close to a perfect air/fuel ratio.

Anyway, ash is only a problem if there is significant oil burning, due to wear or loose piston and valve stem clearances, as in air-cooled engines.

 

[Doug Hillary]

Hi,
Jimbo - sorry your argument is wrong!
The design of pistons and ring position all play a part in deposit formation along with many other design issues
The combustion temperature of modern 4 stroke on-road diesels is indeed very high. Even the exhaust temperature of non EGR heavy diesels goes beyong 600 degrees. No excess of air occurs at all - you must be living in the Detroit 2 cycle era

Regards

 

[Jimbo]

Gasoline engine EGT's run double that and more, over 1500 degrees at peak.

Where are all these ash deposits going to form if you are hardly burning any oil in the first place?

 

[TooSlick]

I wouldn't have any concerns running a 15w-40 commercial engine oil in a gas engine, at least in mild to hot weather. They do have higher additives levels, but oil consumption will be much improved over a 5w-30 petroleum oil under the same conditions, if that is an issue.

Tooslick

 

[Drstressor]

A very thin oil film is left behind in the upper cylinder region after every compression stroke. A function of the lower ring(s) is to scrape (bad term) most of this film down to control oil consumption. As the rings wear and clearances increase, there is relatively more oil film left in the upper cylinder region and more oil is burned. But there will always be some oil in the upper cylinder region that will be burned away during each power stoke even in a tight engine. The EGT of either a gas or diesel engine is far in excess of the oil's flash point so non-combustible metallic detergents will form ash. Most ash is removed during the exhaust stroke in a properly designed engine. However, some piston designs tend to accumulate ash in the "dead space" above the upper ring that can cause the rings to stick.

HD diesel oils typically contain 30-50% more metallic detergent than automotive oils. So theoretically, upper cylinder and ring deposits should form at a faster rate. However, I have never actually heard of anyone having a problem running fleet oils in a gasoline engine. And LOTS of people do this routinely. Most commercial gasolines contain additives (such as Techron) that control deposit formation. Maybe this explains why the higher ash in HD oils doesn't cause problems in gas engines.

 

[cousincletus]

Company I work for bought a 1997 Dodge p/u new and ran 15W-40 Drydene (Castrol?) oil in it from day one. Engine was a 318. Ran the truck for about 150,000 miles before they traded it with no issues.

 

[userfriendly]

I know that everyone loves their multi-grades on this board.
Just to be different I started using CF/CF2/DD149 approved single grades in just about everything including 2000 and newer cat-con equipped gasoline fueled cars.
The ash, TBN and DD levels are not excessively high in these HD commercial engine oils.
Tiggers are made for bouncin',
multi-grades for cold weather startin'.
What kind of animal is this little dancing fluffy guy anyway?

 

[RC]

FWIW - Under a load, a stock Cummins motor can produce EGT's in excess of 1000 degrees. With a few performance modfications 1500 degrees is easily attainable.

I have a question, is the John Deere Plus 50 15w40 licensed with the API? Last bottle I seen at the JD dealer didn't have the API donut. I was just wondering if things have changed.

 

[iskerbibel]

I checked out one of the many partially full bottles I have in the shed- it doesn't have the API donut, but it says in the fine print on the back that the oil can be used when any of a big long list of specs are required, including API SJ/SL... which I guess would've answered my question had I bothered to read the label. On the other hand, I checked out an old bottle of the Case motor oil I had laying around, and it only mentioned API rating CD... I don't remember what the valvoline premium blue that I used to swipe at the Cummins dealer said on the label, but it seemed to work as well as anythig else...

BTW, before I started working as a heavy equipment mechanic(with access to free oil), I used to run either Coastal or Advance Auto Parts oil in most everything... or sometimes super-tech- I've never seen any apparent difference- if it says API SL, oil is oil, right?