Switch Viscosity For Weather?

[Chili]

This will be our first fall/winter with a 4 stroke and I'm curious if I should swap oils due to cold temperatures. We are running Rotella T15-40 currently but I'm thinking as the temps start dropping perhaps we should switch to the synthetic Rotella 5-40. We will see morning temps in the low 30's for some of these races. During the winter he will want to ride at an indoor AX facility but the bike is in an unheated environment prior to riding and could see temps close to 0.

The reason I ask is I've had folks who attribute engine failures to the oil being too thick to make it through the scavenge screens and filters.

 

[Rich Rohrich]

Yes Doug, you need to switch to an oil with a much lower pour point. The easiest way to do that is by changing to a lighter viscosity oil. Many synthetics have a much lower pour point than their mineral counterparts at the same viscosity, so it's worth doing some research before you change. Pour point is the lowest temperature that an oil flow properly at. It's a standard spec that is generally available, so it should be easy to compare with the major brand oils.

That said, the 5-40 synthetic Rotella is an outstanding oil, so if it's easy to get and fits the budget, just use that, :cool:

 

[IndyMX]

Just for sake of discussion Rich, would there be any advantage or disadvantage to changing to a lower pour point or lower viscosity oil in a two stroke in colder weather?

 

[Chili]

The Rotella in both Mineral and synthetic is readily available and I don't see the Synthetic breaking the bank for the amount of hours that the bike will see between now and spring. I'll switch over next oil change. Thanks Rich.

 

[oldguy]

We have always used the same oil regardless of temp staying with a full synthetic 10-50.
This week we are switching to Yamalube 4R because we are having a difficult time finding a reliable source of the Rotella or our old favorite Mobil 1 (and we can now get it at half the price of any of the other synthetics). As Rich is aware we change oil everyday, so old oil wouldn't be an issue.
Are we safe following this practice or would you suggest we find a 5-40/50 as temps are dropping?

 

[Rich Rohrich]

Dave - Most mineral based oils have higher pour points so switching from a synthetic at the same viscosity could potentially cause some issues in cold temps. I would stay synthetic if possible, if not then use a mineral based oil with a lower viscosity.

Just for sake of discussion Rich, would there be any advantage or disadvantage to changing to a lower pour point or lower viscosity oil in a two stroke in colder weather?

Indy - Clutch action might be a little more predictable in cold weather with a low pour point oil in the gearbox. Other than that I don't seeing it matter one way or the other.

 

[whenfoxforks-ruled]

You guys have engines that mix trans and engine fluid,one minus.Chili,you live in a hostile environment(tooo cold) Do not transport out in the cold,or bring a torpedo heater! Any viscosity oil that YOU feel comfortable with below 5 weight should be cool for winter indoor racing,bar the outdoor transport! Try jetting till you do not need a choke or hot start! And for winters sake,make double damn sure that engine is warmed up before it moves!

 

[oldguy]

Rich I believe the 4R is a full synthetic. I'll have to check the bottle to make sure but if it isn't we won't be using it anyways

 

[Rich Rohrich]

Rich I believe the 4R is a full synthetic. I'll have to check the bottle to make sure but if it isn't we won't be using it anyways

Dave - It's a blend of mineral and synthetic.

 

[whenfoxforks-ruled]

Nice pic Rich,leaves little to argue,damn internet! I know Eric has been talking logical,but how about reality,that 500 ain't about squat! Come on modded 450! Casey Sunday,all right! Technically we have never MET! How aboot it!

 

[Jaybird]

If our temps were constantly within a certain range, say like 60f-90f all the time, then we would probably be best using a straight wt. oil such as sae 30-40wt.
The reason being that there are no additives to manipulate the viscosity. The base oil used is essentially the same weight as the finished product.

A multi-grade oil starts out using a very thin base oil that will also have a low pour point temperature. This is anticipation of the startup in winter temps. We need to oil to flow as fast as possible when we start the engine, and without the oil having the ability to flow quickly to the critical points of the engine, wear can occur until it does get there. There may be only a small amount of wear metals created during the few strokes the engine makes before it starts, but this is when the engine is most vulnerable. The majority of an engines (normal) wear is created during startups.

So a 5w-40 oil will be built using a base that has a viscosity of 5wt, and has viscosity improving polymers added that will allow the oil to thicken to a 40wt at operating temps. The problem is that these viscosity changing polymers are very vulnerable to being sheared down from mechanical action. Picture these polymers as little coils that get unwound with use. Once these polymers are "unwound" from shear, they loose their effectiveness.
The greater the spread in numbers of a multi-grade oil, the more of these polymers that have been used to accomplish the task...and oils with high amounts of viscosity improver's may well perform as other oils when new, but shear down faster than an oil with a lesser spread of numbers. A 5w-40 is generally less shear resistant than a 15w-40.
But this is just a rule of thumb...

The base oil used has lots to do with this issue.
Synthetic base oil is much better at handling temp swings than mineral oils. There isn't the need to use the vulnerable polymers when using a synthetic base, so synthetics are far more shear resistant than mineral oils.

Just about any 5w40 oil you find on the shelf will be formulated using group III oil. Group III oil is coined as a synthetic, although it is actually conventional petroleum oil that has been processed to a point that it is as near to coming out of a lab as true synthetics, like POA and esters, are. (Albeit they aren't created in a lab or a magicians hat either, and are derived from petroleum and organic products as are mineral oils)
Some new process' refiners have developed for making group III oil are producing fantastic products for far less production costs than their PAO and ester counterparts.
Especially Shell's grp III bases oils, imo. These grp III oils are also showing to have equal or near equal prowess with cold weather startups as PAO and ester base oil.

Using a 5w-40 of any flavor is probably going to be all the cold weather riding protection one would ever need in any 4T dirt bike.

It would also be a fine choice for the 2T, however we don't have the immediate flow problem we worry about at start of the 4T. A straight weight lubricant is all that is really needed in the clutch box. That is one of the reasons I use ATF in a 2T, which is very heat and shear resistant, and thin enough to perform well at colder temps with nil viscosity additives.

 

[oldguy]

Thanks Rich I always assumed it was synthetic but never really looked that close (to lazy last night to go out and look). I'll be hunting for Rotella this week

 

[Rich Rohrich]

Nice job of summarizing the specifics Jay. :cool:

 

[Chili]

Thanks for the write up Jay, I'm not too concerned about the oil shearing out of grade since we have yet to leave it in this bike for more than 3.1 hours (our longest interval so far). It gets changed at the 2 hour mark on average.

I've used Type F in all our 2 strokes at one time or another and was always happy with the results.

 

[uh_oh]

I just recently switched from 20w50 to 10w40 in mine as the weather is getting colder, if it gets really cold ill switch to a 5w something. Im suprised no one has mentioned valvoline?

 

[camaro_guy_z28]

I'm currently using 80w bel ray gear saver transmission fluid in my kdx should i switch to the 75w for the colder temps in the upcoming months or will it make no difference. Thanks

 

[BSWIFT]

From the affore reasons given, I would think that once the bike is warmed up using a oil with a low pour point, clutch action would determine the final oil to use. This is just a hypothysis.
Ex: Brand A and Brand B synthetic have the same pour point for given temperature.
Brand A has a dragging with the clutch after proper warm up and Brand B has no issue. Use brand B?