Gas : oil mixtures. A general question

[Vic.S]

This question is partly prompted by the 100:1 vs 50:1 argument.

I have always belived that if an engine is being run hard / at high revs then a more oily mix is preferable but if the engine is only run under light loads and at low revs then a leaner mix, if suitable for that particular engine can be used.

In part my belief is based on my undersatnding that with VRO engines the oiling rate increses from 100:1 or even 150:1 when idling to 50:1 at high revs. Maybe I have misunderstood the theory behind VRO.

I am not realy interested in large powerful engines but in the smaller engine sizes so VRO is not something that applies.

I have recently been told that I have my theory the wrong way round and that the more oily mix should be used used if an engine is to be used under light loads and low revs or with log periods at idle speeds while the leaner 100:1 can be used if running at high speeds. The argument for this is that at low revs / small throttle openings very little fuel and therefore oil is being admitted to the engine so it is preferable to use a more oily mix while at high revs more fuel therefore more oil is admitted so the mix can be leaner.

Was I right in the first place or is what I am now told correct.

(Personally I would use a 50:1 mix in any engine for which the makers recommend 100:1 provided it did not lead to plug fouling problems.)

Expert opinions asked for. Thanks.

 

[DJ]

Re: Gas : oil mixtures. A general question

Vic,

OMC recanted their 100:1 mix ratio recommendation shortly after they posted it.

The real reason was that 100:1 does not protect sensitive steel engine components, against corrosion, while the engine is stored or not operating.

The so called "VRO" units did indeed vary the ratio. However, they were short lived in production. They were replaced by an automatic oiler that was set at 50:1.

50:1 is the ratio you want to use. Smoke control is best done by using high quality oils and keeping the engine decarbed and in tune.

 

[reeldutch]

Re: Gas : oil mixtures. A general question

if you mix the gas yourself 50:1 is the ratio.

your understanding that at idle you need less lube and at wot you need 50:1 is correct.
your mixture should never be lean.
always maintain
14,7 : 1 ( Air : gas) in mass. at all rpm ranges this ratio should be the same. not to be confused with oil.
lean or rich is air/fuel ratio.
oil ratio is related to rpm.
more rpm means more friction heat so you need more lubrication to keep tings from overheating and seizing.
the vro pumps are pretty reliable, lot of horror storys not a lot of facts.
they blame the pump but if you ask how or why it failed nobody can tell you the answer.
vro pumps feed the oil/gas mix to all the carbs at the same time.
therefor 1 blown piston is not to blame on the vro pump in a v4 or v6. the ratio is on all cylinders the same.

the problem lays in the maintenance of the vro tank.
water intrucion will kill your oiling system.
periodicly check filters and tank for debris or water.

if you dont trust oiling methods than mix yourself.
you got to trust yourself dough.

ask the experts this question:

WHY do vro pumps fail??????

 

[Vic.S]

Re: Gas : oil mixtures. A general question

Sorry i have asked my question badly.

I am not interested in VRO! Refering to it has caused unnecessary confusion.

I am not interested in any recommendations as to what mixture I should use.

I should not have used the word leaner. I realise it should be reserved for describing the gas / air artio

The question therefore is:-

Am I right in saying that more oil in the mix is preferable for sustained high speed running while less oil may be acceptable for low speed running.

Reeldutch seems to agree with that.

OR is the opposite true namely that running at low speeds requires a more oily mix while at high speed operation a less oily mix may be acceptable.

 

[steelespike]

Re: Gas : oil mixtures. A general question

The faster an engine runs the more oil it needs.As stated much more heat and friction is generated at speed.
Some folks that use a trolling kicker actually reduce
the amount of oil little to reduce smoke and oil fouling.

 

[JUSTINTIME]

Re: Gas : oil mixtures. A general question

no
high speeds more oil
low speeds less oil

low speeds are hard on spark plus causing fowling

50:1
means 50 parts gas 1 part oil,
not 50 parts of oil to 1 part gas

 

[Cricket Too]

Re: Gas : oil mixtures. A general question

Whoever told you that an engine running high RPM needs LESS oil is not going to have their engine for very long. That is equivalent to saying that a higher RPM needs less fuel. Why would you possibly need MORE oil when the engine is running slower.

If that were the case then I guess OMC had it completely wrong all those years that they made a VRO. Because it ran 100:1 - 150:1 at idle and 50:1 at high RPM. And I guess they have it wrong now that they make a OMS pump, since it's 50:1 all the time, including high RPM, and maybe slightly leaner (oil:gas) at idle, maybe 75:1.

Your thinking is correct, your friend on the other hand.......don't let him work on your engine.