I have been working with 2-stroke engines for quite a while with a motor oil that has doing a great job. It was kinda simple since there was literally only 2 different oils at the gas station for 2-stroke. Recently I've gotten a Honda GX-35 engine which is 4-stroke. I have been going to my local gas station as well and noticed that there is a plethora of different oils (same brand, different types). While it was quite obvious which one is the right for my small GX-35 engine (described as motor oil for small engines like generators, light diesel or gasoline engines) I was wondering about some of the descriptions of the other oils.

The point that struck me most interesting is the fact that the different oils had different statements about the exhaust system you should be using for that oil. For example one oil mentioned, that it is very light for high performance but requires a very modern exhaust cleansing system and is not compatible with diesel particle filters. So this made me think: What causes this different exhaust requirements? Do some oils not fully burn out or burn to particles that could be toxic (thus modern exhaust) or not burn up in the particle filter?

  • "different statements about the exhaust system" This only applies to Diesel engines.
    – Moab
    Aug 24, 2020 at 19:43
  • I guess this was worded badly then on the motor oil? Because the statement was literally "for diesel or gasoline engines with the most modern exhaust systems. Not compatible with diesel particle filters" Aug 24, 2020 at 19:45
  • Out of curiosity: What makes it not compatible with a DPF? Remnants that dont burn in the particle filter? Aug 24, 2020 at 19:49
  • I have never seen this statement on oil products but sounds like a bunch of marketing nonsense to me.
    – Moab
    Aug 24, 2020 at 19:50
  • I am going to go the gas station tomorrow and create some images, maybe it is worth a laugh what they put on there :) Aug 24, 2020 at 19:51

1 Answer 1


Oils have various additives. Some of the oils in 4 cycle oil form ash if they are burned in combustion; elements like zinc and barium . Because all the 2 cycle oil will be burned it is formulated with no "ash" forming additives. I expect using 4 cycle oil in a 2 cycle engine for many miles would leave ash deposits someplace.

  • Thanks for the info, the GX35 is a 4 stroke engine, so I am going to use 4 stroke oil for 4 stroke engines and 2 stroke for my 2 stroke engines, not going to risk anything there. I assume some of the ash that could happen with 4 stroke motor oil might not be burned in the DPF and this is why some are not compatible with DPFs? Aug 24, 2020 at 20:24

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