Pump Oil change question

I have 67.8 hours on my pump so far so im about 18 hours late in changing the oil. Will that be a severe issue? Also can’t get general pump series 100 oil so I bought “Comet Premium pump oil”. Any issues with that? The gp oil is supposed to be 30W non detergent. None of the oils at northern tool list the weights. I know simpson brand is a different weight.

Also my pump oil is draining like molasses. I ran the pump for about 5-10 minutes to drain some of the tank. Is this normal? Manual says crankcase capacity is 31oz. So far after 15 minutes i have less than a water bottles worth.

Make sure the cap is off. Much faster to use a vacuum pump. But, you don’t need to charge it again for the live of the pump, only at the 50 hour break in.

Dipstick Cap is off. I was worried its so slow to drain because I waited to long to change it or something. I’m concerned less than 31oz of oil drained. I’m not sure if it’s the max capacity of the case and the fill is less than that. The manual really doesn’t give any detailed information for pump oil changes.

Don’t ever buy that comet junk again. Go to O’Reilly’s and buy a gallon of 30W non detergent oil and you’ll be covered for a few changes. I change mine every 250-500 hours. Not because it needs it. But because I like to service everything I own regularly.

Yes, it takes forever. Harbor Freight sells a dirt cheap hand pump that will suck it all out in no time.

No, 18 hours over isn’t going to hurt anything at all. Again, some folks like IBS literally never change their pump oil and they’re still alive to tell the tale.


Let it drain until nothing else comes out then refill to the red circle in the middle of the sight glass. I like to go just a smidgen above the red circle. And I mean just a smidgen.


Ditch the 30w non detergent oil. I know its the recommended oil but i was shown to use 15w40 rotella t diesel oil. It works way better. The non detergent oil was always a dark grey when changing as if some internal seals were wearing or something. After using the 15w40 it always comes out gold like when it was put in. I change my oil definitely within every hundred hours. And about the low amount that was removed from your pump @KDAL_Tex. When things are new they will absorb oil and its normal to have to add oil during break in periods

Under no circumstances follow the above advice


Please don’t do that. I know you’re trying to be helpful but what you just told him is bad advice and you won’t be the one footing the bill when something goes away.


I guess my 4 years of experience with it and no problems is a fluke. Question @DisplacedTexan @Innocentbystander. Why not?

It is a fluke and you probably don’t put many hours on your pump The reason why is because people smarter than you and I engineers and whatnot decided what oil it took a friend of a friend that tells you to use something else is fine for you but don’t screw over a new person that doesn’t know any better it’s okay for you to ruin your equipment Don’t do it to others

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Not sure what pump @SWFLWasher is running, but my direct drive AAA pump does indeed state 15w40 oil is to be used. I realize that this style pump is untypical for this industry, but there may be a few others who have them.

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Just a funny meme

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15w40 is the same oil as the oil that simpson sells for their direct drive 4gpm units. However belt driven units at 8gpm have a different oil and from everything I’ve read it’s 30W. I think different pump manufacturers have different additives. I’ll return the comet. I got some 30w oil from a store that sells General Pump powered washers so it should be a good enough match. It is 30w.


I got the information from a vendor thats been around longer than youve been washing. So ill keep doing me and you do the same. But i have noticed a big difference in my oil when it comes time to change. It almost looks the same as when i added it. @PPWofLexSC i run a belt drive 4 and 8 gal. Although the 8 gal only has 20 hours on it. I used the 15w40 for a thousand hours on my 4 gal and thats enough proof for me but it was actually the first time i changed the oil that i was convinced

I mean, if you change it in 100 hours (other than the initial break in), shouldn’t the oil still look pretty clean anyway? I’d need a full time oil change guy :confused:

Also, always at least err to the side of the people who designed and made the thing. They have no motivation to give you anything but the best info, and they have the most tech knowledge on their product.

I believe the manufacturers would also suggest to maintain oil changes throughout the life of the pump at specified intervals. But @Innocentbystander says never change the oil other than after the 50hr break in. So sometimes they’re right (the manufacturers) and then hes always right (because he knows all). Whatever.


Well, I’ve been in the pressure washing industry for nearly ten years now and you’re the first person I’ve ever heard recommend using detergent oil in a system designed for non-detergent oil. I’ve spoken with technical advisors for one of the largest equipment manufacturers in the industry on multiple occasions and none of them ever recommended that and they know considerably more than I do.

As to the why, it’s very simple. Detergent oil is designed to be used in combustion engines to capture combustion byproducts and keep them in suspension in the oil itself. This is to keep soot and sludge from adhering to surfaces. Detergent oil also has much better drainback properties so that the oil can drain back to the pan and keep the oil pickup fed with an ample amount of oil.

Non-detergent oil does not capture any combustion byproducts. It does not keep them in suspension. It does not have a high drainback rate. This makes it ideal for air compressors, pressure washer pumps, etc where there are no combustion byproducts. It has significantly better cling factor to help keep the oil on the moving parts instead of flinging off of those moving parts. It is specifically designed and recommended by literally everyone for these specific reasons.

In short, what you recommended is just not even remotely a good idea and the fact that you’re recommending it to someone that’s newer to the industry is not right and you’re not the one risking anything but he is if he followed your advice. Again, I know you were trying to be helpful but you’re out of your depth on this one. And that’s okay. We’re all here to learn but giving bad advice is not good for anyone.


Do wha, huh???

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Direct drive pumps are an entirely different animal and, yes, some of those do run on 15-40. However, those pumps are not germane to the situation being discussed by the OP here.

YouTube never heard that either, huh?