So Im talking with this guy who is a Diesel Mechanic on big rigs, he claims that by using diesel oil in a gas motor it will clean the out the motor(if you always have dirty looking oil you would do this) You would run it for a couple days and then put normal oil back in. He claims that diesel oil has a lot of detergents in it and this is what cleans the motor out. I personaly dont know much about diesels so I would like to know if anyone can back this up.
Also he claims that using synthetic oil drys out the seals on motors that were originally not meant for it. He sounded pretty convincing at the time buut now Im wondering.

 

idk about the synthetic stuff drying up the seals.

BUT

My friend runs diesel oil in his truck (1977 Ford), and it seems to work great year-round.

 

Isn't that Rotella stuff really thick?

 

the synthetic drying up seals doesnt sound right, from what i hear synthetic does tend to find leaks that regular oil couldnt get through, i think thats what he is talking about.

 

I used to do fleet maintenence for a local shipping company, and we used Valvoline 15w40 Diesel fleet oil in everything from Detroit Diesel's in tractor trailers to Ford 5.4L V8 gas motors in E series vans. A lot of the vans had 250-350k on them and ran good.

 

I used to run the Rotella 10W30 in my '87 it was sometimes hard to find but was the best stuff. If your going to run dino oil it is your best choice IMO.

I run synthetic in my '94 and it does seem "thinner" then an equivilant grade of dino oil...

idk about the seals drying out though...

 

The synthetic thing is true on older vehicles as in mid-80s and older. It won't dry them up per se, but standard seals of that day do not like synthetic oils. A lot of those older engines had seals that needed oil to make them swell in order to keep them tight and well...sealed. Ever buy an old 80s or 70s car that sits for a while? They always develop leaky seals because the seals went a long time without being lubricated so they dried up. Synthetic oil doesn't have the same reaction with older seals that dino oil did.

Newer seals these days are much tighter in the first place therefore running synthetic or dino, you will have the same results.

I ran Rotella T in my Yamaha motorcycle and took off the pan...unbelievably clean for an engine with 43K hard miles. Diesel oil has TONS of detergents. That mechanic was not yankin your chain.

 

I would think that the diesel oil has lots of detergents since those motors need that. Look at the diesel fuel. It even looks oily. I would think if you are running it in a motor that doesn't need it you might be compromising lubrication due to too much detergent. Just keep up with your oil changes. I pulled my valvecovers and mine is spotless with zero sludge.

I pulled open a for 4.2L with 239K miles. The guy changed the oil every 3K. He even used cheap oil like Valucraft and other non-name brand. The engine was very clean also.

 

Well, I hate to tell hate to break it to ya, but that's WRONG!

And what makes you think a diesel engine requires a LESS lubricating oil? Ahhh....right....didn't think that one through did ya?

FYI, ALL diesel oils recieve the SAME certifications as non-diesel motor oils AND meet diesel motor oil certifications. ALL are recommended by the manufacturer to be used in "mixed fleet" applications. "Mixed fleet" meaning vehicles with either GAS or DIESEL engines.

Research...

 

just make sure you use the right viscosity oil cause if you use 15-40 in engine that calls for 5-30 its not going to be a good thing, things that need oil wont be getting them

 

Diesel oil does a better job of keeping soot or other byproducts of combustion in suspension. As for synthetic causing leaks it has to do with the fact that the detergents in synthetic will remove buildup in the engine - thus if there are areas that would leak once all that crud is removed then yes you will have a leak there.

 

Well there are C-rated and S-rated oils. C oils are for Compression ignition (i.e. diesel engines) and S oils are for Spark ignitions (i.e gas engines). There can be C-only oils and S-only oils and then there are universal oils that have both a C and an S rating, for example CF/SJ or whatever.

As long as you run a universal oil with an S rating equal to or higher than what your gas engine recommends, then it is fine. There are some diesel-only oils that have additives in them that can harm engine sensors that gas engines have. Since many diesel engines have no smog equipment on them, they can run oils that have special lubricating additives that would otherwise be harmful to delicate electrical sensors. And likewise, many gas engine oils have no C-rating and primarily lack the soot suspension additives (TBN) and those oils would not work will in a diesel, since they would let the soot fall out of suspension and form deposits inside the engine.

I often run a universal oil (15W40) in my 22RE. I also have a VW diesel and find it easier to just keep one kind of oil around.

 

I'm not saying that diesels need less lubrication. I'm was saying that MAYBE using diesel oil in a regular motor would result in less lubrication since there is so much detergent in that oil.

 

A diesel engine typically requires a more lubricating oil, high pressures in the cylinders, higher forces on the pistons/rods/crank, higher combustion temperatures, etc. Not so much that you have more detergents in diesel oil, rather there are more dispersants that keep the soot/dirt in suspension. As long as the "diesel oil" has an S-rating equal to or greater than what the gas engine mfg. specifies, it is OK to use it.

 

Detergent WITH the oil is a better way to imagine it. I'm quite sure if a diesel motor oil is certified to be used in a gas engine it's perfectly safe to use in one. On that note...

I knew I should have been a little more specific...fair's fair.

"ALL" was a bit of an overstatement. What I could have said was "ALL you are likely to run acrossed" or "ALL widely commercially available" as in your Delo 400, Rotella-T, Mobile Delvac 1300, etc.

 

As long as it rated for your engine your good to go. Ive ran Amsoil Series 3000 which is diesel and gas engine rated for a few years and has held up quite nicely.