PREMIX by Mathematics....Best Ratio ?
 

Ok, I have researched this several times on the forum (by search) and a couple of times by posting a question of "how much". This is what I have come up with and perhaps others have too.

I have been driving rx7's for the past 20 years and I add one quart of motor oil on an average of 1200 miles. Certainly the whole quart does not get used by the OMP as there must be some used by the engine itself and a little leakage here and there (older cars usually do, on the average). But for the sake of discussion lets say that whole quart is used for OMP.

I get on average 20 miles per gallon of gas with combined highway and city driving. This means that it takes me approximately 60 Gallons of gas to travel that 1200 miles and use that quart of oil. That being the case, when I do the math I am getting:

1200 miles on 1 Quart of Motor oil divided by
20 miles per gallon of gas equals
60 Gallons of gas for the 1200 miles traveled

There are 32 ounces in a quart and when I divide:

32 ounces motor oil divided by
60 gallons of gas, this equals
.53 ounce per gallon on gas or approximately
1/2 ounce per gallon of oil used per gallon of gas

I have been using 1/2 ounce of 2 cylcle (TC3 rated) oil per gallon of gas or 16 ounces for a tank full (my tank is 16.6 for 1988 S/4).
In my opinion this PREMIX is more effecient than the drip, drip, drip of a heavier weight motor oil that is not even mixed with the gas. With the injectors spraying this consistent mix it would seem to be a better way to evenly distribute the oil into the intake system thus giving a more even distribution.

This is considering that at times on or more of the OMP lines may be leaking for whatever reason, perhaps clogged, partially or completely, OMP gasket or banjo leaks or improper vacuum in the system due to old and ineffecient vacuum hoses.

As usual, I always ultimately wind up with great input from the forum and would really appreciate opinions of this particular PREMIX ration of 1/2 oz 2 cycle oil per gallon of gas. Thanks in advance, now cut loose guys and gals.... :git:

I don't think you understand how the poll function works,

But have you comparied a warm 30W oil viscosity to Pre-mix viscosity??? Why do you think motor oil is heavier???

And

The amount of oil injected through the MOP is based on Throttle position or Load (depending on series), so if you did not use any throttle past 1/4 when driving your oil injection amount would be near 0, so your rough math falls flat on this.

Yes Sir, I need to study on how a poll works for sure. Putting math aside, do you think that my ratio is a safe level ?

I know people that run less than you even, but I'm not really sure what level is safe. I just run 1oz per 1 gallon and not worry about it.

Most people run 75:1 to 125:1 depending on the intended use of the engine/car. Richer mix for harder treatment on the engine such as a track day or a backroad blast, lighter mix for easy driving such as highway miles. I'd say 100:1 is suitable for mixed driving.

Aren't you lucky Mazda did the R&D for you already?
It's something like 300 cc / min?
It's written up in an SAE paper...try ACRE mirror site.


-Ted

Since a 100:1 ratio is .75oz per gallon of gas your .50 is right on with Kevins 75:1 ratio meaning your consumption is fine and in order but one the thin side. Aparently you drive light footed and highwayd. Eaither way a little more premix would be on the healthy and wori free end of the stick.

OOPS!
Try 80 cc / hour...



-Ted

that's at WOT for one hour, not relative to real world driving. :p:

100:1 is fine for mixed driving.

Plus I think RETed touched on this.. But 2 cycle engine oil at ambient temperature is slightly different than 10W30 or even 20W50 in the pan...
But also keep in mind that while the oil injectors inject more oil at WOT, so do the fuel injectors (obviously) - more oil will be going in at WOT anyway.

Also, 1 oz per gallon seems to keep my cars running just fine.. i think this falls under the leave well enough alone category ;)

I have been using 1/2 oz for every gallon for the most part with no problem. Sometimes it is 1 oz per gallon. There is no right or wrong answer here. You will find that 99% of the people who premix in this forum use between 1/2 oz & 1 oz per gallon.

My question to anyone which oil do people use, my 91 has been getting Pettit pre mix, and my 90 was getting some from Wally world. What should I use adn will it hurt to change from one to another. Thanks

^ search debated endlessly. I use Klotz

penzoil synthetic marine 2 stroke for me at 1oz per gallon.

Harley...maybe I just missed it...

But you put motor oil in the gas tank?


I didn't know motor oil would stay suspended in fuel like two cycle stuff does.

James

wankle7 i think u did miss it i think he said he puts 2cycle TC3 rated oil

i use Waldo's world 2 stroke oil for DD and i use Redline synthetic when i feel like mashing the pedal through the floor.

been using 1/2 per gallon for a while using wally world 2 cycle, but the omp system is not functioning and leaking, so ill be removing it and going up to 1 oz. per gallon here shortly. just my .02

1 oz. per gallon here. It's already time consuming enough getting gas, waiting in line etc. I just have a little bottle that has the ounces on the side and after I get gas depending on how much I just take the can out and dump in a 1oz to 1 gallon ratio. Makes it way more simple when you don't have time for math :)

ps. nice to see someone else from lousiana on here. We need to start a louisiana rotary group.

No, I said in my post that I am using 2 cycle oil with a TC3 Rating in my gas. I was just comparing that to the consumption of the motor oil via the OMP to try and come to an approximate ratio factor for a safe and proper amount...and you are right that motor oil would not suspend well in the gas or at least not as well as TC3 rated 2 cycle oil since it is made for that.... :)

Even 2-stroke oil will settle. But, Rx-7's aren't stationery. Normal driving caused fuel sloshing along with fuel circulation will keep everything mixed up. In an emergency, if metering pump is disabled, any oil is better then none so don't worry about the "settling" issues.

The old Racingbeat catalog mentioned oil ratio vs power. The more power you make, the more oil you need.

The one ounce per gallon measurement is a simple failsafe. Its probably too rich for a typical NA, just right for a stockish T2, and probably a little lean for heavily modded engines.

There are two reasons why I wouldn't base my premix ratio on my calculated MOP injection ratio.

Issue #1, oil injection variables:
The problem with using the engine's oil consumption when creating the premix ratio is that you need to make sure your entire oil injection system is in spec, prior to doing your oil consumption per mile test.
Have you removed and tested your clogged oil injectors? or the metering pump flow rate per the FSM?

Issue #2: TCW3 and API/SAE motor oils-- not the same
2-stroke oil and motor oil are different enough. 2-stroke is usually thinner and includes additives for combustion cleanliness and mixability with fuel. For equality, you'll need more 2-stroke as premix when compared to the direct motor oil injection from the MOP.

My recommendation:
If your stock MOP is connected and working, use 1/4-1/2 ounce per gallon.
If the metering oil pump is disconnected or disabled completely, use minimally 1 ounce per gallon for engines under 200hp. Increase reatio incrementally as power is increased--for example 1.5oz/gallon for 300hp or 2oz/gallon for 400 hp.

I will probably be using a 100:1 ratio when I get the car running. I have heard of some people in and around STL not premixing and not having an OMP/MOP and their cars are still running fine...... I personally think they are idiots though.

Mr. Deadrx7conv....Issue number 1....about 1 qt per 1200 miles is what my rx's have averaged in approximately 1,000.000 miles of driving so I have assumed that the flow at that rate is adequate since I have not had any problems related as yet.
I do agree with all of your analisis completely and would think yours should be the standard on PREMIX...Thanks
Case Closed