b_met

I have been looking into the archives, searching for THE answer to this question. I find different views, so here is my decision making process. Please choose, and feel free to give ideas for either side. I'm leaning toward premixed, just because I am already in the habit of buy good oil for my quad, but we'll see what happens.


Here are some points I feel are relevant.

Engine wasn't designed to have premix, if it ain't broke don't fix it.
Premixed will be a pain in the butt to keep up with.

Premixed will reduce smoke and carbon deposites.
(My favorite) Premixed will keep you from putting nasty, burnt, engine oil into your combustion chambers.


If my thoughts here are wrong, please let me know.( Like I had to give that invite, huh?!?)

b_met

Preixed....damn.

RotaryRyan

Its really not that hard. After you do it for a while you get use to it.

r0tary noob

also, if your OMP fails you have no way of knowing it until your engine dies, premix all the way

rotary emotions

I have never heared of an OMP failure, so I guess there's no real reason to go premix. I personally wouldn't go through the hassle of mixing oil in the fuel every time I fill up the tank. Since I never tank the same amount, I'd be constantly counting out how much oil I need. BTW don't forget putting oil into fuel LOWERS the octane rating of the fuel!
There's one important reason why the standard system is not good: it draws dirty oil from the engine. Even if you regulary change the oil, it won't be perfect anymore by the end of the cycle. The sollution is an adapter piece, and a seperate tank. Then you can use two stroke oil to inject.
http://www.rotaryaviation.com/oil_in...p_adaptors.htm

Unsupa

iTrader: (2)

it's not so much that the omp fails, but the gasket around it leaks pretty bad not letting oil get into the motor. that's how mine is anyways..

Stevan

iTrader: (17)

The oil gets mixed with the fuel either way, but the premix oil is made to burn, provided you buy the right oil.
I can imagine it would be a little trouble to try and put and put the same amount of fuel in each time, or calculate and measure for each different amount.
Another thing to consider is that you have to check and add oil every 1000mi. using the omp.
I'm going to try the preIxed, you can always change back if you don't like it anyway.

RotaryRyan

I think youll like it

kettlman

iTrader: (2)

well heck. looks like pre-mix ha the majority of the votes. yet i still rely on the omp. yea yea if it fails i'm in trouble. but hey, i check my engine all the time. check my oil every other day. if the omp fails, well all you gotta notice is the clear tubes don't have oil in them. not that difficult. and the omp is designed to run up to 7500 rpm's i believe. so why goto the extra truble with pre-mix. it costs more, takes time(not just putting it in but goin out and buying it). and what if by chance for some reason you forget to add it, or someone else forgets to add it? that would really suck. i know how i get when i'm in a hurry. i'm suprised my boat still runs. when you run out you think, well i should have enough till next time. if you ask me, the omp is there for a reason, to give the right amount of oil when you need it. not the same amount all the time. so here is some other thoughts for you to pounder.

bouis

Check your OMP and make sure that it works. If it does and your engine has a hundred thousand miles on it, there's no point to premixing now. If you get a new block built with $1000 worth of brand new rotor housings, use premix.

alien_rx7

I premix. Haven't seen a lick of oil in those OMP tubes since I've had the car. Of course I've never tested it, and I do have a slight oil leak but it is slight since it only loses a quart about every 3k+ miles and I already know my oil cooler is leaking too (which has nothing to do with OMP, but with the leak statement).

Also, I wouldn't worry about octane. It won't be enough of a drop (maybe 1pt if you're lucky) and since you're engine is still NA (no boost) it is best to use the lowest octane anyway. I always joke if I could get 86, I'd put it in (Sunoco use to sell it).

Bolox

i premix...

i love the funny looks i get when i pull out the bottle of 2 stroke from the hatch...

RotaryRyan

The only i dont like about premix is when you have to prepay for gas. Then you have to sit there and multiply in your head what your gallons are gonna cost.

mcnannay

i never measure it out, i figure pouring in half a quart on a full tank will suffice

like alien_rx7, i too have never seen any oil in my omp lines...so ive just been premixing ever since ive owned it

id probably be fine with just using my omp if it worked...

cdrad51

Most small 2-stroke engines are lubricated this way, chainsaws and leaf blowers, for instance. So were 2-stroke motorcycles and outboard engines. Then, someone figured out that injecting oil into the intake stream could be more efficient and convenient.

When there is little load, little oil is needed. When load is high, more is needed. Mixing oil with the gas serves this function in a broad sense, as more fuel, and thus more oil, is consumed under higher load. However, there really is much less oil needed under typical conditions, whereas quite a bit is necessary at the highest loads. And, at idle, an engine runs much richer than under most other light duty conditions, but it consumes much more oil than necessary if it is mixed with the fuel. Oil injection simply offers a better match between oil required and oil supplied.

Race cars have different requirements than our street cars:
Idle time is low; Idle quality doesn't matter; Reliability matters a lot; Combustion chamber deposits matter little, as race engines get rebuilt frequently; & The engine is operated at or near peak load most of the time. Mixing oil in the fuel provides an adequate match between oil needed and oil supplied under such conditions. And, one more potential system failure can be avoided, besides a little weight saved.

Another thing to consider on this subject is that less oil than needed can cause excess wear, or even a blown engine. More oil than necessary can cause a blown engine too. Huh? If yours is a turbo, you want the most octane you can get. Oil acts as an octane reducer, so too much can bring on detonation you might not get otherwise.

Those who still want to mix oil in the fuel instead should know that any oil you buy for premixing with your rotary's fuel that is claimed to be a "special" formula probably isn't that special. The same properties that make a highly desireable small 2-stroke oil also make a highly desirable rotary oil: easily mixed and stays mixed with the fuel; burns cleanly, leaving behind few deposits to build up in the combustion chambers or foul spark plugs; and minimal octane reducton.

The most highly stressed racing rotaries run without oil injection have oil mixed in the fuel at a 100:1 ratio. Ratios up to 160:1 are acceptable for less severe racing service. Full oil-rich from the stock injection pump is roughly 150:1.

alien_rx7

This is where knowledge comes in handy. If someone is running a boosted engine and premixing, they really need to know what they are doing. Mixing in a normal (rich) 150:1 mix should only derate the octane by a point if that. Of course I don't have data on it but only heresay, I'll leave it up to the reader to do the research for now unless I can come across some hard data.

So are you advocating using synthetic 2-stroke oil then? This is the only 2-stroke oil I know of that meets your criteria except for possibly fouling the plugs.

Agreed. In fact I've posted nearly the same thing in a couple of other premix threads, just do a search on my name and premix The book How to Modify Your Mazda RX-7 has a discussion on this subject.

Myc1972

Hello guys!
One thing i am still unclear of is:

Can you premix if you have a catalytic converter?

Will it harm their life?


Thanx!

hornbm

premixing will kill your cat

The way I premix is I just fill my tank, look at how many gallons went in, then add 1 oz per gallon of 2 stroke or MMO. IF I put 12.5 gallons in, I add about 13 oz of MMO

The mmo bottle has the side marked off in 4 oz increments so its really easy to measure out how much you need

Poor the mmo in, put the cap on, and shake the rear a little bit to mix it up. Normal driving will mix it just fine.

Its stupidly easy to do, I dont know why you guys would ever complain about it, there is no calculation!!!!

1 oz per gallon!!! 12.5 gallons is 12.5 oz of MMO

Ive been doing this for 10,000 miles and the motor is just as strong as when I finished the break in!

RotaryRyan

I know, its so simple!

I usually put the oil/MMO in before the gas. I know its not the best idea but i like to know its mixing real good.

Stevan

iTrader: (17)

hornbm,
there is no calculation if we choose "your mix ratio", 128:1, 1oz. per gal.
If we choose to run 160:1, .8oz. per gal., there would be some, not exactly calculus, but calculation just the same. Unless, you memorize the amount per gallons, .8,1.6,2.4,3.2, which I guess wouldn't be that hard either. But measuring it accurately would.

Here's an exerp from How to Modify your Mazda Rx7.

alien_rx7

I love that book. It's my #1 book on the shelf for my 7 stuff!