Hi guys,
Thanks so much for all your input. I just got myself a Honda GX390 pressure washer the other day. I bought this oil ‘Speciality Engine Oil 199-2002’ to put into it but half had leaked out on transit to my house so I bought this oil and topped it off with it - Engine Oil 1L 4 Stroke | Toolstation
When starting it off for the first time, it took a couple of tries before it eventually fired up. I only had it on for like a few minutes before I could smell burning and seeing white smoke coming out. Is this because of the oil mixup?
First, Honda spent millions of dollars in R and D to find an oil that worked best in their engines. But Honda oil. Second, don’t mix oils and third, you probably overfilled it.
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Really appreciate your response. What’s the consequences of mixing oils?
Should I just empty it out and refill with the right oil instead of use the mixed oil already in there?
Correct, drain out all the current oil. I would then recommend to run the honda oil through it briefly, drain it and you should be more than good. But white smoke is oil burning and never a good sign, IBS is right though you more than likely just overfilled it.
Honda doesn’t have an oil refinery, no reason to spend extra for oil that says Honda on it. Phillips 66 makes their oil if you really want to stick with what they sell. Buy your favorite brand of 10W-30 and stick with it
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I agree, I feel like oil threads get out of hand quickly so Honda would be the less controversial choice but I actually really like the Blue bottled Shell Rotella. Ran Lucas oil then Maxima growing up racing but a few years ago I was having issues with missed shifts on my KX450 so a buddy recommended the Shell Rotella. I was hesitant but after doing some research and then trying it… I’m sold! Even run it in the race bikes now, cheaper than the “Higher End” oils and works great. Personally though I think as long as you maintain it at the recommended service intervals or even a bit more often; that will be much more important than the brand. Even the best oil in the world won’t last forever!
Exactly, in the end, especially with these small engines, the brand doesn’t matter. Failures occur from lack of oil or never changing it, not because you ran Mobil instead of Castrol. Heck, the grade doesn’t really matter much either. My car says I can run anywhere from 0-20 to 15-40 diesel oil. I actually run Walmart’s Super Tech in a few things. It’s really cheap but has good reviews. Depending on where you live, it’s either made by Mobil, Pennzoil or Warren.
It’s a 340 BMW. Guys running a lot of boost go 15-40. I’m only an extra 4psi on my tune and I run 0-40 over the recommended 0-20.
I use Honda oil only, Tbh its cheaper than anything else on the shelf. Even at home depot
If I can save money and time it’s a no brainer
Thanks for your replies guys, I guess I will go ahead and empty it out and use the recommended oil. I can see some honda oil on amazon. Hopefully this is good - https://www.amazon.co.uk/gp/product/B00G8LP6OA/ref=sw_img_1?smid=A1T0PM98PJF63P&psc=1
I’ve been running VP Synthetic 10w 30 in my GX390 forever with no complaints. I get it Tractor Supply.
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There you go. Not sure if your machine has a spin on filter. If it does, only use Honda. Completely different back pressures in Honda filters versus NAPA, Fram etc.
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This is also very very true and often overlooked! The variance of flow rates between OEM and aftermarket filters can be substantial. A family friend owns the local Aprilia dealership in tulsa and he and his son showed me a few RSV4’s that have blown up due to oil starvation and they all had one thing in common… non-OEM oil filters. Aftermarket filters can actually have more/denser filtering but at the expense of the flowing less oil. Its pretty uncommon but can happen with the more temperamental engines.
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Folks believe that all oils and filters are the same until they research or have something like that happen. You can rest assured that Honda, FoMoCo and others all add their own blends and additives to their oils to make them unique to their specifications.
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Interesting. Have you heard anything from the guys running 15-40 about issues with the cats after running that oil? Most diesel oil is compatible in gas engines but usually the emissions systems have some issues with it.
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No because most guys running 25-30 psi of boost don’t have cats 
Even just running a stage 2 tune it’s mandatory to run either a high flow aftermarket catted DP or catless. No need to run that thick of oil with only a stage 2. It’s the guys really pushing the boost that use it.
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Just buy decent small engine oil. Small engine oil had less foaming detergents than car engine oil. (This is not be be confused with non-detergent, or ND oils like what you would run in your pump). Oils from Kohler, Briggs, Kawasaki, Honda etc likely have a “SK or “SL” rating on the label, where as car oils will likely be “SM” or higher. If you go to your local small engine repair shop they will have something on the shelf for you. You may pay $1-2 more for the quart, but how many quarts do you plan on going through in a year?
That’s what I figured. I’d be surprised if you could actually run diesel oil in a car with intact emissions.
Also do I need to empty the fuel in the tank first before emptying out the oil?
