80w-90 vs std 2-stroke oil

[Scuba602]

I’ve heard conflicting opinions on the use of 80w-90 gear oil instead of standard 2-stroke oil.

Please let me know what you know, think, have heard or otherwise! Good bad or indifferent !!

 

[butre]

it's a dumb idea. gear oil is too viscous and sticky for use in an engine. best case scenario it just robs power, worst case it can't even make it through the carburetor jet and the engine won't start.

 

[Steve Best]

Actually it is not the viscosity, it is that the base stock and additive package are totally unsuited to 2 stroke use.
Gear oil is measured on a different SAE scale from motor oils so actually:

Not that viscosity in premix really harms anything.
It is noticed on cold starts but the cylinder runs so hot that it isn't a problem with a running engine.

The problem is the additive package.
Back in the early 1950s most oils were relatively pure mineral oil with little additives so that you could specify SAE 30 motor oil as a 2 stroke oil. Even back then gear oil was typically not used because of the aditional additives. Not so these days with larger and more specific additive packages. As well, the multigrade oils such as 10w30 and 80w90 are basically a thin oil with VI improvers that are essentially plastic! (polymers) These don't handle combustion well. Same with many of the scuff resistant additives which are often metal based. This makes for oil that burns with a lot of charring that can be conductive and may foul rings and plugs. Totally unsuited for 2 stroke use these days.

Two stroke oils are specifically made to be low ash so they don't foul rings and plugs. Conventional mineral 2 stroke oils use a different base stock (name eludes me at the moment) and synthetics are a a different formulation from 4 stroke or gear oil. The additives and considerations are completely different as well.

I should mention here that "autolube" or "injector" 2 stroke oils are designed to be "thin" (less viscose) to flow through the injector system at cold temperatures. This design parameter is more important than engine protection, so not my favoured oil choice.

 

[entity]

If the original poster was actually serious, and not just a troll,
then wouldn't just the smell of that stuff in the jug be enough to discourage you ?
I can't imagine what it would smell like burning .......

 

[Frankenstein]

If the original poster was actually serious, and not just a troll,
then wouldn't just the smell of that stuff in the jug be enough to discourage you ?
I can't imagine what it would smell like burning .......

I believe he is serious, however I don't know the very specifics of that type of oil but my best guess is no. My thoughts are similar to your's, the oil used in a 2 stroke needs to be a bit more robust against temperature and pressure in a cylinder and crankcase lubricating bearings.

Gear oil also is meant to hang around and has qualities that make it good for that, on a 2 smoke the oil has no reason to stick around long and so the additives would be very different and in in different amounts..

Would smell and smoke like hell too.

 

[Scuba602]

It does stink.

And I’d run in in a 49cc, lil extrA smoke but no stench.

It works if you have nothing else around, like I did.