OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Trimmers and Brushcutters McCulloch Trimmers & Brushcutters 2 Stroke Oils

I have always wondered what is the actual difference between the air cooled 2 stroke oil and the water cooled 2 stoke oil , and is there any real advantage of sticking to the correct labeled 2 stroke oil

MMMM not sure for a fact, but I reckon the Sthil 2 stroke oil (air cooled motors) is just re-labled Castrol TTS which is a synthetic oil for both air and water cooled. I am aware that some outboard oil differs slightly in its make up to allow for some very minor moisture related issues but then again Yamaha Yamalube is used in their air cooled racing two stroke kart motors (@ 15-18000 RPM) and their STD water cooled 2 stroke outboards!! go figure?

I suspect for the most part it is marketing for marketing's sake, to try and sell oil on a contrived point of difference. My family had a Shell servo for ~12yrs basically the motto was to go well ... screw shell But I digress.. the engineers tech info sheets gave the marketing guy's away... BS for the most part; but the bottom line on oils was that you got what you paid for..... hope that helps..

As a general rule stay away from Castrol R30 Racing oil (try some hehehe, it smells great) as it is a castor oil synthetic blend which will gum up your motors with continued use (and help your bowel actions as well ).

that r30 sure does smell great too still smell it now ! must hang around in the 'case for a while . but they dont seem to like marine oil much , took a tank or 2 to get rid of a few problems with an old one i had that was run on it . ok now , been running on valvoline ..

Thanks for the info , i tend to agree with you on marketing side of things , there seems to be a wide range of colors or dyes as well in the oils ,all of this is enough to make you walk out of the shop empty handed and have a think , but i know one thing now is that i will keep away from the R30 ,
Thanks a heap 'FAST GRASS' for the reply ,

I know an electrical trade teacher that runs fish and chip oil in his two stroke mower engine & swears by it.
I would love to strip down his engine and inspect it though.

Imagine the nice smell !! i think the neighbours would start to line up at the front door to put an order in for some chips !
But i also would like to see the condition of the engine as ,

Air cooled two strokes tend to run at a higher temp and have greater variations in temp due to ambient conditions. Once up to temp a water cooled motor should remain at a constant temp internally. Improves the abilty to tune it, also improves engine life as there is a greater control over tollerences, not so much of a compromise.

If you have a hot air cooled two stroke and you throw a bucket of cold water on it you can seize it.

And outboard motors vent their exhaust into the water so thats where the oil goes and that would definately warrant a different formulation.


If anyone would like to take mechanical related advice from someone who knows about electrical thats fine. And a teacher no less. Cant comment on this person in particular but there is something sepcial about someone who never leaves school. I know a guy who drove Coaches for 20 years, he now teaches warehousing courses and B-double licences by parroting what he learnt in books. Look out world.

Two stroke motors need two stroke oil. Not sure how you would even keep Fish and Chip oil mixed in petrol.
Just like diesels run on diesel. Enviro fuel used to do my mate a roarin trade.

Just about all racing engines used to use castor oil in the sump until the early 1950s, because prior to the various additives being included, mineral oils were just not as good. That is where Castrol took its name from, of course - they named themselves after the best oil available (except for whale oil, which was even better, but extremely expensive). There were problems with castor oil though. The worst of them was that when it got very hot then cooled down, it coated the main and big end bearings with varnish. The varnish then melted the next time the oil got very hot. It didn't all melt at once though, and sometimes the result was a broken connecting rod. (The problem was minor if the engine was run on pure methanol fuel, but because vegetable oil is chemically incompatible with petrol, using the two together was very risky.)

Using vegetable oils such as cooking oil in modern engines is destructive - they can be excellent lubricants, but a chemical nightmare in petrol engines. Because the oil and fuel are incompatible, I would not expect them to mix well so in a 2 stroke mix, lubrication might be quite patchy, as well as the varnish formation problem in hot spots. It doesn't matter much with cheap engines whether they get ruined or not, but putting it in an engine that is worth keeping is just dumb.

Thanks Grumpy & Rob,
Didnt know about Castor oil being used, I looked castor beans up on the net, interesting, a vegestable oil, boiling point 313 deg C.

Yes, I can imagine air cooled engines requiring an oil that has to withstand high temps.

The fella I mentioned above, well, I will get his mower for parts one day.

Well we had this discussion at work today and one of the guys who is a mechanic by trade handed me a hand full of paper work and said read this and make up your own mind , so i did , an found it a worth while read , Here are the 2 sites where they came from ,

http://www.sea-doo.net/techarticles/oil/oil.htm

http://www.ultralighthomepage.com/OIL/oil.html ,

I hope you guys find it as interesting as i did ,

Thanks David, Yes interesting,

outboard oils = higher levels of heavier base oil -
because of higher piston temp.

air cooled = lower levels of heavier base oil -
to stop rings sticking & excess muffler deposits.

Thats what I got out of those articles.

I havent read the articles, no time just now.


but yeah i had that wrong.
Air cooled VS watercooled.

Air cooled is vairable.
Watercooled is at a constant, closer to optimum, so higher temp better performance and effiency.