We have all these discussions about brands of oil, but what happens to an engine that is run with poor quality oil, in other words what does one look for in an engine tear down that shows the effects of running it on "bad" oil?

Hard, glass like, carbon deposits, heavy, dark brown to black carbon accumulations, some blocking almost the entire exhaust port. Severly scored cylinder walls from carbon particles breaking loose and being pulled down the cylinder below the piston ring. Stuck piston rings, heavily scored piston skirts. Rough bearings. Engines difficult to tune that have poor ring seals from thin oil ratios. Engines that "cold stick" easily from thin oil ratios poermitting the piston to heat up faster than the cylinder.

I'm not trying to start a fight, T.O.M., but what you are describing is often caused by mixing Brand X 100:1 formula oil at ratios much lower than 100:1, such as 40:1. I've seen people bragging in print on the internet (no - not you) about giving their engines "extra protection" by over loading their engines with way too much oil. Then they ***** and complain that Brand X oil is garbage after using it incorrectly and loading their engines up with the glass hard deposits that you describe.

Plain black carbon build-up is not typically considered a defective symptom in mineral base lubricated engines. I'd rather have to disassemble and remove carbon, than to run a synthetic oil that removes metal from the engine in accelerated wear.

Yes, I know that some synthetic oils have approached the barrier of providing clean engine service without permitting excessive engine wear and that that is what we are talking about here. My point is that just a little deviation from the recommended gas/oil mix ratios can provide extremely unsatisfactory results in some instances. That, and it is a Wednesday morning with nothing much to do today - so have at it! (smile)


Ed Cregger

I thought synthetic oils were supposed to protect engines from wear more, not less. Please, bring me up to speed on this statement. I've apparently missed something.

Very generic statements.
Synthetic oil make less carbon, but its very very hard.
Dino oil makes more carbon but the carbon is very soft and easily removed.
About the worst thing you can do is to run a Synthetic 100:1 oil at 40:1

But it says right on the brand X bottle that you can mix their 100:1 oil at heavier ratios down to 50:1 on the chart. Guess they should remove that if it is only a 100:1 oil! Of course, their Dominator product is intended for 50:1 or heavier ratios.

I don't use the stuff but I have read the bottle.

It is a well established fact that if you mix synthetics at heavier ratios than recomended - you will get hard carbon formation

Not disputing the fact that these oils can produce hard carbon, just stating what is listed on the bottle. Seems just wrong that reading instructions can get you into trouble! Thats why I don't use brand X 100:1 oil!

I can wipe the carbon off the tops of my pistons with a rag ..... Pennzoil user at 40:1. Just did that with my 5 year old DA-50.

Does anyone look for the effects of using no airfilter. Or is this also blamed on the oil?

Not to get off the subject too far but our engines breathe the same air we do. Unless you live in an area where you fly in gritty sand storms I don't think ingesting a few small bugs or pollen will hurt our engines.

Ever find a need to pick your nose after a day of clean air flying? More dust in the air than most recognize.

Yes I was a bit generic in my descriptions of what happens with various oils and how they are used. I don't have the time or patience to write a 25 page dissertation on the effects of each and every oil I have tested or worked with. If someone wants to pay me for my time I'll treat it like the job it is and get it done. Yes, there are oils that do little to protect an engine from excessive wear. There are also engines where the quality of plating is so bad no oil can protect them from excessive wear. Some engines have cylinder metals so soft that hard carbon particles leave long smooth ridges under the exhaust ports after only a couple hundred hours. How does one discern the difference? It can be tough, especially for the uneducated.

Brand X says it can be mixed from as low as 50:1 to the recommended 100:1. They don't say that it won't form more carbon at that level. ;-) Sometimes what isn't said is as important as what is said. Crafty devils these label writers!! Gotta watch'em every minute.

An item that most miss is that racing oils were designed for people that race. As such, some of those oils do not contain much in the way of detergents because the people that use them get inside their engines on a very frequent basis, taking care of various things in the process. Great lubricants and cooling agents but not the best for long term, unattended use. People serious about their two stroke engines might be getting inside them and making adjustments to components after every run or two.

The average R/C two stroke user will be lucky to see the inside of their engines only once during the entire use and ownership period. Many will never see the inside of their engines. Lazy, fear, short of time, doesn't matter, they don't get involved. They prefer that caring for a mechanical product be an automated process. So there's no one miracle oil that's suitable for everyone. You have to learn something about various products to determine what will work the best for you. However, some oils are pure garbage over the long run, with the long run being more than only a couple hundred hours.

I have to admit, I was using Outboard oil in ALL my two strokes. I have since been told to, STOP IT! and I have followed this advise, although, I'm not sure why.

My rational was: Outboards are a fairly high performance engine so there oil should provide good wear protection. Outboard oil has good anti-corrosion additives and I buy it by the gallon, so I only had to have one kind of oil in my garage.

I had engaged in this practice for many, many years with no discernible problems. None of my power equip. has ever seen the inside of a repair shop and some weed trimmers and blowers are over 20 years old and there used weekly every season.

I have an old chainsaw in my garage (came from an old, long since gone relative) that ran its whole life with diesel tractor oil for lube. He used the same stuff for chain lube too! I doubt the gas / oil mix was ever really measured with any accuracy so who knows what the ratio was. That engine looks great inside and with a carb and ignition rebuild would run well today. I know oil is important but sometimes I think that for our hobby use, people put way too much stock in selecting the "perfect oil"!

It is like all hobbies. People look for something to obsess about. Some just don't know. Some are just looking for something to argue about. Some are looking for the magic bullet. Some ,like me, just pick put the nearest reasonably adequate item and use it. Much less stress that way and the equipment doesn't know the difference.

Truckracer, you hit it on the head. Lots of folks get too anal retentive over this oil topic. If the engine is fit correctly, it will last a long time even if the owner burns straight 30 weight non detergent automotive oil (not two-stroke oil) at a decent mix ratio. If the engine is fit poorly, or assembled defectively, no oil in the world will be able to increase its lifespan.


Ed Cregger

This thread should be relocated to the "Oil debate" area of the forums....with the other 10,000,000,000,000 threads just like it. I read posts in this thread that gave me deja vu...over and over again.

I think the best advise is to stick with the oil that has so obviously worked well for you. Go back to it and quit listening to all the experts.

Regarding the outboard oil use in aero engines. Outboard oil was designed around an engine having a water jacket that was constantly moving a cooler fluid through the engine to moderate heat. The oil does not have to be as good at heat collection as one used in an air cooled engine.

As for using engines many years without ill effect, one must evaluate the different between years of use and hours of yuse. Then you have to factor the use time "continuos" and the engine loading. I know that many feel that adding a propeller "loads" an engine, but to what level of a load? Fine pitched props don't provide as much load as a coarse pitch. Large diameter props load more than small diameter. Adding a generator adds even more load. Heavy planes load more than a light plane.

Lots of factors influence what is done to and with an engine but most people don't have a clue what is going on with their propulsion systems. They've never had to know, therefore they never learned. In the last 10 years or so it's all been about power to weight ratios. if you had more than 1-1 the plane would always accellerate straight up. What happens when that power to weight falls to full scale, production, light aircraft levels of .2 to .4-1? Suddenly one needs to know and pay attention to what is taking place in their engines.

The hobby manufacturers made the equations easy. You didn't need one, all you needed was an aircraft weight and an approximate engine size as provided by the kit manufacturer. That's still more than some currently understand.

A customer sent in his Q-35 for a make run cause it wasn't running right. He was right not much power, so I took it apart and it was just wore out, the chrome was wore through. Ah must be oil abuse, called the customer ans ask what oil he was using. Wanted to add it to my list of junk oil. He said he what ever Wal-Mart had on sale, buy a couple of qt, use it up and go get something else. OK well how old is the engine? Don't know, bought it used about 15 years ago and just fly it every weekend with good weather. It probably had 1500 hr on it!!!!!!
So there is a lot be said for any approved oil at 32:1 Don't sweat the small things.

The HP/weight ratio of the 65 Aeronca 7AC Champ was .0537. They climb and glide at 60 and cruise at 70 or 72. With a GW of 1220 lbs.

This is certainly not the performance we enjoy from our models.

A few years ago a wise poster here on RCU summed up the oil debate quite eloquently when he said something like this: "All the major brands of 2-cycle oil when mixed according to the manufacturer's recommendations work equally well, but the one I use is the best!"

Yup, I've got no less than 6 partially used bottles of 2 cycle oil because this guy said that and that guy said this. Now I just use whatever I want. Currently and for the last 2 years I am using Amsoil because I like the smell of it, and that's all the reason I need anymore!!