Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Adding 2 stroke oil to diesel fuel

Adding 2 stroke oil to diesel fuel

Adding 2 stroke oil to diesel fuel

I seeking some factual info - good and bad - on the current trend thats sweeping across all the car user forums on the web - adding 2 stroke oil to diesel.  I thought this Forum could add some reality to all the "its works for me" type of posts you read elsewhere (Google it, they are endless !).  

Its the new snake oil - or is it ?  I've actually tried it in my Nissan TD42 and it does seem to have an effect.  The engine is quieter and pulls better.  Although I've not proved the lower fuel consumption bit yet, its looking good, certainly not worse.

So whats going on ?  Why does adding 2T oil to ULSD suddenly make the engine seem a different beast ?  Why does no manufacturer recommend this ?  Why does the current ULSD respond to this treatment when the fuel suppliers say the fuel already has lubricity alternatives to the sulphur thats been removed ?  Surely if a simple mix of 2T solves problems we need some facts from the fuel makers as to whats wrong with the current ULSD blend ?

Answers guys, and sorry if its already been covered, post me the link, I searched but didn't find anything.

RE: Adding 2 stroke oil to diesel fuel

and forgot to add, is there any possibility that using 2 stroke oil (1:200 ratio) will cause any damage ?  The only thing I've see is not to use it with DPF set-ups.

RE: Adding 2 stroke oil to diesel fuel

The only thing that I do with my '91 Cummins is to use a "diesel additive" with each fill up to add a bit more lubrication to the pump since we are now using a very low sulfur content fuel. I have a bunch of 2 cycle oil...guess I could try that.  It's oil and not much different than the commercial additive...cheaper?

Don't know the exact mileage on my Dodge...Bought it new Feb. 1991 and the odometer "died" about ten years ago at 186,000...I checked the valve lash at 110,000 and change oil and fuel filters regularly. Runs just fine. Certainly has paid for itself!


RE: Adding 2 stroke oil to diesel fuel

I don't know whether it works or not. It's not being recommended by the manufacturer because an unapproved additive can put more sulfur in the fuel tank than is in all the fuel, might be illegal, and certainly the manufacturer did not certify the engine that way.

Unmodified oil can be 5,000 ppm sulfur or greater, which is 300 times more concentrated than the fuel. I doubt that 2 tablespoons of anything makes a difference though.

RE: Adding 2 stroke oil to diesel fuel

Guys, I suggest you try it.  I was very pleasently surprized on just how different the engine feels and drives,  all on the face of it for the better.

The keys are: 1:200 ratio.  Use a mineral based 2T as sold for saws/mowers (cheaper the better !) etc and not the boat outboard motor stuff and not synthetic.  Don't use it in engines built in / after 2007, althought this is up for debate as users with CRD motors are reporting benefits.  I think the key there is not to use it if there is a DPF.


RE: Adding 2 stroke oil to diesel fuel

I don't know offhand what's actually going on, but your description that the engine "feels and sounds" better says to me that you're likely affecting the rate of pressure rise in-cylinder.  Additional lubricity would not, in my opinion, make an externally-discernable difference.  

That said, I'm not sure what would account for a change in the rate of pressure rise given what you've said you've done to the fuel.  Things which might be involved:
 - change in fuel viscosity and therefore amount delivered, spray pattern, and droplet size
 - change in combustion characteristics of fuel (ignitability, injection-combustion delay, etc)
 - quantity of energy released (but how much difference could 0.5% make?)


RE: Adding 2 stroke oil to diesel fuel

1:200 ratio doesn't seem typical online.  An example from another forum: "I use a mix of 1 quart 2-stroke oil, and 1 quart of Power Service Diesel Kleen per tank of fuel - EVERY fillup!"

I don't know how big his tank is, but I suspect it's less than 200qts (probably more like 80qts).

RE: Adding 2 stroke oil to diesel fuel

A diesel engine will run on a remarkably wide range of fuels, but that doesn't necessarily mean it's a good idea for emissions, durability of seals, etc. If you can make them run on waste vegetable oil (for a while) you can make them run on straight motor oil ...

Using an excessive amount of 2-stroke oil probably won't damage anything on an older non-emission-controlled diesel with no catalytic converter. But I doubt if it will do much good, either.

RE: Adding 2 stroke oil to diesel fuel

Sounding better could be due to heat release shaping.
Feeling better is probably subjective, based on the above.

Adding unspecified cack to fuel may or may not improve the lubricity of the fuel, but pumps and injectors generally outlive engines. anyway.

I always used to pee into my compost heap.

- Steve

RE: Adding 2 stroke oil to diesel fuel

you can make them run on straight motor oil
there are kits for large trucks (mining, etc) that cause the engine to consume a controlled amount of its own oil along with the fuel, so that clean oil can be continuously added and oil changes avoided.

RE: Adding 2 stroke oil to diesel fuel

A major oil leak into the cylinders on a diesel can actually cause a runaway engine.

The two stroke oil is formulated to lubricate when mixed with fuel and to burn with it. The combustion products do no harm to 2 strokes. It could be safely assumed that no damage would occur to a diesel where components are similar. Exhaust emission controls on modern diesels will be different to the exhaust components on a 2 stroke.

In my opinion (without supporting data) the 2 stroke oil will burn as fuel. It may very very slightly add to lubricating properties of the fuel and maybe benefit the fuel pump/injector but almost certainly not to a detectable nor measurable degree.

At 200:1 its effect on burn rate, fuel viscosity and energy content should be unmeasurable.

Any change to perceived performance will be due to placebo effect.


See FAQ731-376: Eng-Tips.com Forum Policies for tips on use of eng-tips by professional engineers &
for site rules

RE: Adding 2 stroke oil to diesel fuel

"Use a mineral based 2T as sold for saws/mowers (cheaper the better !) etc and not the boat outboard motor stuff and not synthetic."

Well cheaper means more brightstock and less/no polybutene (no smoke), and maybe less dispersant.  High molecular-weight polybutenes have been used as anti-misting aids, perhaps arguing against a droplet size effect.  Not outboard means that anti-corrosives spoil the effect, which suggests a surface activity effect, but 'not synthetic' seems to exclude ester stocks, which should be more surface active than brightstock.

One may conclude the anecdotally based recommendations seem to be pointing in conflicting directions as to what the active ingredient may be . . .

How might 2T oil affect cetane rating?

RE: Adding 2 stroke oil to diesel fuel

In one post I found this.

Use 2stroke oil with the following spec:
Low ash < 0.05%
Dont use fully synthetic
Outboard stuff was a no-no in the European posts, but in the American posts it seems to be OK !

I must admit to not knowing anything about 2 stoke oil specs and there may be typos in the above.  There was mention of Mercedes having done some work on this, andI think the above specs may be from that work - dunno ?

RE: Adding 2 stroke oil to diesel fuel

I had a case of unwanted 2 stroke oil to use up,and put a litre in every full tank of my 4D56 powered Pajero.I noticed no difference in anything.Although when I sent my injector pump in for overhaul at 300,000km ''just because'' - they said it was in perfect condition and didn't really need a service....just new seals and calibration.

RE: Adding 2 stroke oil to diesel fuel

The "2T oil" was the type, not the quantity. blllttt

You should absolutely never do this in an engine designed for ULSD. At the 200:1 ratio, your catalyst could be seeing 2.5 units of sulfur for every designed 1 unit of sulfur, turning your 250,000 mile catalyst into a 100,000 mile catalyst, voiding warranties, and opening yourself up to other trouble. At a more realistic 50:1 (or other similar 2-stroke type ratio) your catalyst could now be seeing 7 units of sulfur for every designed 1 unit of sulfur, turning your 250,000 mile catalyst into a 36,000 mile catalyst. With one good high-sulfur slug (say you add too much with a low fuel tank) and you can actually brick your catalyst within a few hundred miles (it's at least partially recoverable but the controls won't recover it because they won't know what happened).

RE: Adding 2 stroke oil to diesel fuel

Old timers used to change the oil in their semis and then dump that ten gallons of used oil straight into their fuel tanks, Sure there is always metal particles but that is what fuel filters are for and Many a truck went hundreds of thousands of miles doing that. Now to today. My buddy worked for a company doing deliveries with isuzu box trucks and he filled one up once with 87 octane gas of course he got in trouble! Well one day he calls me, Man this truck is losing power! It won't barely get to 45mph!! I said you filled up with gasoline again didn't you? He thought for a second and looked at the fuel reciept and yep More than a half tank of 87 octane! I told him to hurry up and get off the highway and find a dollar store. I had him buy a like 4 quarts of motor oil and dump it in. He said it started running better but it was still popping and barely accelerating, So I had him pick up some more. I forget how many quarts he eventually used but it was all the money he had.  The truck actually ran better than ever he said and noone at the company was the wiser. I don't recommend using gass and oil mix but a diesel will run on a wide range of fuel and as long as you don't have a particulate filter adding some motor oil won't hurt anything two stroke or crankcase oil!

RE: Adding 2 stroke oil to diesel fuel

[I take it your Pajero was pre current pollution laws for diesels.]

We have no pollution laws in New Zealand - EGR's are plugged,and cats cut off.

RE: Adding 2 stroke oil to diesel fuel

I agree with Patprimmer; this is just placebo effect.  Witness the thousands of satisfied users of those $19.95 magnets placed over the fuel line to "align" the fuel molecules.  I never trust anyone that says their engine "runs better", because it is almost never true....

RE: Adding 2 stroke oil to diesel fuel

that may be, but I've also found that people who are familiar with engines are quite good at hearing and identifying changes in the sound of those engines... much better than a lab guy with a herd of accelerometers.   

RE: Adding 2 stroke oil to diesel fuel

Okay....It is now Wednesday and I put a pint can of two stroke oil (Sears brand, no idea who actually made it. It's been on the shelf for several years) last Saturday.  The 30+ gal. tank was just below the "half full mark" and today is about "one quarter" (my odo broke about ten years ago so I don't know how many miles...I get 21 MPG usually).

To bottom line this-----I don't see, feel or, hear anything different, unusual or strange.  Nothing! Nada!


RE: Adding 2 stroke oil to diesel fuel

I agree that people may be able to hear/detect subtle differences in engine sound.  That said, I don't believe anyone that says they can detect a change in sound or performance by going to a 1:200 ratio mix of oil and diesel vs straight diesel. This is snake-oil effect at its finest hour.

RE: Adding 2 stroke oil to diesel fuel

Rod -

Obviously, the pedigree of the oil is why you felt no improvement.  If you had dumped in some Torco, Castrol or really old (like me) Steen C you might have been plastered to the back of your seat.  

This kind of stuff has been going around for some time and the Dodge/Cummins (Turbo Diesel Register) folks have pretty much come up with the same results you did.


RE: Adding 2 stroke oil to diesel fuel

It is well documented and repeatable that if you get your blood alcohol content up to about 1:300 you can be plastered to the back of your seat (although you shouldn't get in your car then). Don't go for 1:200 or you might be dead.

RE: Adding 2 stroke oil to diesel fuel

OK guys, hold back, snake oil it is then.  I knew I could rely on you lot to put me straight !

To put a slightly different twist on the discussion, whats the best way of adding some sulphur back into ULSD for the old timer motors that need this for lubrication ?

Once you've got the sulphur levels back up (is there a limit ?) do you need to consider what spec of sump oil you use to cope with the new sulphur ?

Or is there some other way of getting the fuel system lubricated ?

Or maybe, I'm just worrying unnecessily !

RE: Adding 2 stroke oil to diesel fuel

Maybe the nostalgic smell from the exhaust makes the car feel nicer to drive?  I used to really enjoy passing cars on my RD350 on full throttle, giving them the joy of fully synthetic 2 stroke oil.

- Steve

RE: Adding 2 stroke oil to diesel fuel

Ultra Low Sulfer Diesel in most western countries is supposed to meet a specification for lubricity, measured by an apparatus called a High Frequency Reciporicating Rig. So prolly the best way to put your mind at ease is to get your diesel from a reputable supplier.  I have some familiarity with the test method (from a project looking at gasoline instead of diesel), and my experience is almost any lubricity improver will move it at very low levels.  0.2-0.3% of vegetable oil will boost lubricity significantly.  Although that is a pretty low level, I don't know it wouldn't affect low temperature properties or long-term injector fouling.  The commercial additives used at fuel terminals to adjust ULSD lubricity have had extensive no harm testing.  It's not hard to improve the lubricity of ULSD with additives, just expensive from a terminal point-of-view.

RE: Adding 2 stroke oil to diesel fuel

Also, as I understand it, it's a myth that sulfur itself acts as a lubricant. It's a holdover from the original process that was used to remove sulfur when "low sulfur diesel" (500 ppm) was first implemented ... the process accidentally removed other compounds that are the actual lubricants. When the process was corrected, the problem went away. ULSD should not have this problem because the issue is well known now. So, it isn't necessary to "add sulfur" to ULSD for older engines ... only to ensure that the ULSD meets the standards for lubricity, and as noted above, this should only require buying it from a reputable source.

RE: Adding 2 stroke oil to diesel fuel

I can only add my experience with my own Dodge, a '91  one ton duelly.  Bought it new in Feb '91, odo quit at 186k sometime around 1999/2000 so I'm guessing it has something less that 400k on it now.  Never used much additives as I never saw/felt any improvement.  The thing still runs as new, not much smoke, no oil used between services...I hate to say it but it's been over a year since I last changed the oil (I'll get to it, Pat D, promise). Still on the original heater and radiator hoses.  Replaced the serpentine belt a couple times, a couple brake jobs, Flushed the tranny a couple times (you cannot drain the TC without drilling and tapping in a drain plug) did the valve lash once at 110,000.  That's it.  It just goes and goes.

Major costs in the last 18+ years---One LR wheel bearing, one RR brake drum (broken brake adjuster), one RF brake rotor (broken brake pad), one oil cooler hose (abraded) and, of course since it's a 90's era truck, all the paint blew off it and it was repainted about ten years ago.  That's it, good truck.

I think I'll just continue doing what has worked well for the last 18 years. Maybe I'll look into fixing the odo.  Naw...When the "Low Fuel" comes on I can still go an easy hundred miles and that's plenty of time to refuel.  Oh!  Did I forget to mention that the "fuel guage" is a bit dyslexic?


RE: Adding 2 stroke oil to diesel fuel

not necessarily the same as what happens in fuel, but...

How Do EP Gear Oils Protect Against Wear?
EP gear oils contain additives that prevent metal surfaces from cold welding under the extreme pressure conditions found in situations where boundary lubrication prevails. At the high local temperatures associated with metal-to-metal contact, an EP additive combines chemically with the metal to form a surface film that is ductile enough to prevent the welding of opposing asperities and prevent scuffing or scoring that is destructive to sliding surfaces under high loads (Figure 1). Chemically reactive compounds of sulfur, phosphorus and sometimes chlorine, are used to form these inorganic films.

didn't read it ($12): http://www.sae.org/technical/papers/902175
Fuel Sulfur Effects on Diesel Engine Lubrication

Lubricant additives: chemistry and applications

RE: Adding 2 stroke oil to diesel fuel

Once again, based on some internet posting (it must be true or it wouldn't be posted) and the results of the "butt" (seat of the pants) dyno, someone has bested all the automotive and petroleum engineers in the world.  What would I do without the internet?

RE: Adding 2 stroke oil to diesel fuel

... you'd need to get all your information from a bloke in the pub.

- Steve

RE: Adding 2 stroke oil to diesel fuel

I'm with Somptinguy ( and probably of the same era). My buddy and I used to add a bit of Castrol "R" to our XT500 four stroke singles just for that special aroma. Can't guarantee it ran better - but sure smelled good...

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Engineering Report - Top 10 Defect Types in Production
This 22-page report from Instrumental identifies the most common production defect types discovered in 2020, showcases trends from 2019 to 2020, and provides insights on how to prevent potential downtime in 2021. Unlike other methods, Instrumental drives correlations between a variety of data sources to help engineers find and fix root causes. Download Now
White Paper - Addressing Tooling and Casting Requirements at the Design Stage
Several of the tooling and casting requirements of a part can be addressed at the design stage. If these requirements are not addressed at the design stage, lot of time is spent in design iteration when the design reaches the die caster. These design issues lead to increase in time and cost of production leading to delay in time to market and reduced profits for the organization. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close