I put hydraulic in the generator instead of oil but what should I do next

I accidentally put hydraulic oil in my generator during a oil change however I caught my mistake before I started the engine so I drained the hydraulic fluid and put in regular 30 weight oil my question is how do I proceed should I run it for a short time and then change the oil again or just do another oil change before I start it

I  would drain it out again without starting the motor.  Once you start the engine everything is going to get circulated. I would not worry to much to be honest!   Drain it, fill her up again and forget about it. 

I have a different take on this.

I would run the engine intentionally to circulate and dilute what little hydraulic oil is inside, mixing the tiny amount with the new 30W oil.  Run for 15 minutes to allow the fresh oil to capture any dirt and remaining dirty oil that didn't come out when you drained the old dirty oil.  Then drain it hot and put in the right oil.

Why not take advantage of your error and use it to flush the engine?  Since you drained the hydraulic oil out, there is so little remaining that it would do no harm.  In-fact I wonder if the only difference is the lack of detergents in the hydraulic oil.  I read somewhere that automotive oil is 1/3 other ingredients, mostly detergent.

I think I will run it a short time and drain and replace and keep my fingers crossed. Thanks for the input

I  would drain it out again without starting the motor.  Once you start the engine everything is going to get circulated. I would not worry to much to be honest!   Drain it, fill her up again and forget about it.

Ditto.  the slight bit left after the second drain will be negligible.

the slight bit left after the second drain will be negligible.

I feel the slight bit left after the FIRST drain will be negligible, hence run the engine with 30W for 15 minutes to gather what little remains along with any dirt and original old dirty oil.  Utilize the first refill of 30W as a flush.

Quote from: Volkemon on July 16, 2019, 04:52:18 am

the slight bit left after the second drain will be negligible.

I feel the slight bit left after the FIRST drain will be negligible, hence run the engine with 30W for 15 minutes to gather what little remains along with any dirt and original old dirty oil.  Utilize the first refill of 30W as a flush.

Sorry, I thought this would be the second drain of the oil, the first being the initial oil change, quoting Ragoodsp's post.  I missed that you had enumerated them differently. My bad.


OP never mentioned, but the generator DOES have an oil filter, right? OR is is no filter, and detergent free oil? (like air compressors)

IMO, the 'danger' is running hydraulic fluid through the motor.  Running a mix that you KNOW has hydraulic oil in it does not seem to be the best option for me.

Out of curiousity, I just mixed up some conventional 10w-40 motor oil (rotella-t) and some aw68 HYD fluid, no dye.  They dont seem to have a big density difference, and seemed to mix up well. Does not look like the fluids combine, but they do homogenize. I will leave them for a bit to see what happens.

** That was 8:15, 8:30 has the HYD fluid forming a layer on top, judging by the smell and viscosity. The stuff that was a homogeneous mass has cleared up, so maybe there was some combining?  Dunno.  I still would avoid running the combination in my equipment. Will keep the glass on the bench for a few hours.

9:!5 - they have definitely combined, there is a bottom layer that is ~95% of it, and it is 'clear' to see through, not distorted. There is a small layer on top of the mix, maybe 5%, that has separated. It is has a high viscosity, like motor oil.  Less dense, it is floating on top.

What the heck, I will leave it on the bench until lunch. See what else happens.

In the re-read of the thread, I see I missed this - (pre-coffee blur)

I think I will run it a short time and drain and replace and keep my fingers crossed. Thanks for the input

So the deed is proily done already.    Hopefully we get a follow up!

THANK you for the help and going over and above on the mixing info. I am staying at a RV park and I have not had chance to run the Gen. yet I will let you know how it goes. My plan is to run the Gen for 15min then change the oil again run it for 30min and change it yet again. I will keep you advised

No problem!  Sorta my OCD special anyway... 

Well, the entire glass of fluid did mix, except for a bit on top. You have to tilt the glass to see it, but there is a layer that did not mix. Everything else did.

Into the used fluid bin with it. Good experiment. Now when people ask what happens...I know.

  I get many comments like "HOW the heck do you know this stuff?   I try it. Thats how.   Generally NOT at home....   

Curious as to your reasoning for running it with the contaminated oil.   But anyhoo... Good luck! Hope it works out well. 

I am not running anything with contaminated oil that could have been a typo. I’m at RV park in Lincoln City OR where we are parked in like cord wood so no work can be done until we leave this park. My plan is to run the Gen for 15 min with the new oil change then drain and replace with new oil and then run for a 30 min then put new oil once again hope that will work. I will let you know

I agree with Herr Dittmer, use this goof to do some crankcase cleaning. Anyone else recall back in to old days, when we would add a small amount of transmission fluid (say about 1/4 quart) and then run the engine prior to an oil change?  The detergent in the transmission fluid would help remove crud from the crankcase.

- CD

Cropduster, yep.  I'm sure old enough to remember that trick.  I also remember a product called "Casite" (not the Casite motor honey I think they still make and sell).   I am talking about a big black can to clean your carb BFI (Before Fuel Injection) back in the Fifties.   You took off the air breather, goosed the engine to a pretty high rpm and slowly poured this stuff down the carb.  Black smoke in "Call the fire department!" quantities would shoot out the tailpipe and those old motors would gasp and try to die and you just played with the throttle linkage a bit to keep it running.   I also remember one older guy down the street that poured water - yes, water- straight down the carb with the same playing with the linkage and he claimed it was the perfect solution to clean the engine.   I never tried that and was told to avoid Casite and the water if your engine was near worn out.  That was defined as 20,000 miles without a ring job.   When people talk about the Good Ole Days, I usually thing of things like that...……..and rayon tires.

Speaking of doctor-in-a-bottle products, many years ago I bought a used 1986 Pontiac Fiero-GT with the 2.8L-MFI engine.  I used DeKarbonizer, a valve-cleaning product that as I recall, worked this way.

1) start the engine and warm it up to normal operating temperature
2) have someone sit in the driver seat and maintain, I think it was 1500-2000 rpm while you use the product
3) take off a vacuum line on the intake manifold close to the throttle body
4) insert an extra long vacuum hose from there to the bottle of DeKarbonizer
5) with a pliers, pinch the hose and release the fluid such that the bottle empties within a specific period of time, like maybe two minutes.

The white smoke generated during consumption was tremendous.

Prior to the treatment, the engine required premium fuel to avoid the engine knocking/bottling sound.  Afterward, I could go back to spec regular.  The product worked great.

I agree with Herr Dittmer, use this goof to do some crankcase cleaning. Anyone else recall back in to old days, when we would add a small amount of transmission fluid (say about 1/4 quart) and then run the engine prior to an oil change?  The detergent in the transmission fluid would help remove crud from the crankcase.

- CD

  I recall a quart of kerosene.  Then there was a product called Rislone still sold today.  I wonder if it is simple kerosene, ha, ha.