How does GTX have such low viscosity?

[RamFan]

I've looked at the info from the "Improved Viscosity Chart" post that I made a while back, I then used the PQIA page to ensure validity of my data since I was skeptical about the GTX values. My data checks out.

I then decided to compare synthetic 5w30 oils to GTX 5w30 using the widman calculator and am seeing that the GTX values are almost the same as synthetic 5w30 values. I've checked up to -20C.

How can a conventional reach such low viscosity numbers? One of the major selling points of synthetics is the low temperature start up protection, however GTX is proving that it is just as good as synthetics in this respect, yet it can be bought without the synthetic premium. What gives?

 

[dtt004]

Hi.

It all depends on the quality of the base stocks. Conventional oils of today have come a long way since synthetics were first introduced and marketed.

 

[jorton]

GTX is very popular but they have silly tv commercials.

Now that all of the Majors have reformulated for api sn I don't know what's what. Do Mobil Special and Super have the best volatility numbers, like Superflo and Clean 5000 had? And is wb still most volatile? Until PQIA does new comparative testing I don't know which brand I'd be most comfortable with.

 

[edhackett]

Data derived from calculators that only use 40C and 100C data are only valid between about 36C and 110C. Values calculated for temperatures outside of that range cannot be considered true values.

Two points define a straight line. The actual viscosity of the oil does not follow a perfectly straight line, especially at the extremes. Base oil type and additives such as pour point depressants cause the oil to behave non linearly.

Ed

 

[fsskier]

Castrol Product Data sheets show:

GTX 5W30 Pumping viscosity: 40,000 at -35C
Castrol EDGE 5W30 Pumping viscosity 11,524 at -35C

The above poster is correct, the guesstimator is well beyond its accurate range.

My street elevation drops about 1 inch every 5 feet, that is accurate for the whole block. That would put Denver about 25,000 feet below sea level.....if you wished to extend the guesstimator that far....

 

[RamFan]

Originally Posted By: jorton
GTX is very popular but they have silly tv commercials.

Now that all of the Majors have reformulated for api sn I don't know what's what. Do Mobil Special and Super have the best volatility numbers, like Superflo and Clean 5000 had? And is wb still most volatile? Until PQIA does new comparative testing I don't know which brand I'd be most comfortable with.


Mobil SN oils are thicker then their SM counterparts from what I've checked. I have not looked at the other oils though.

 

[RamFan]

Originally Posted By: fsskier
Castrol Product Data sheets show:

GTX 5W30 Pumping viscosity: 40,000 at -35C
Castrol EDGE 5W30 Pumping viscosity 9900 at -35C

The above poster is correct, the guesstimator is well beyond its accurate range.

My street elevation drops about 1 inch every 5 feet, that is accurate for the whole block. That would put Denver about 25,000 feet below sea level.....if you wished to extend the guesstimator that far....


While it is true that these calculators are not exact science I think they may give a good idea of how an oil will perform.

Your elevation example is not quite the same. Elevation will go up and down, elevation at 3 feet down your block is 3 inches lower then foot one, but at 6 feet down your block it may be 2 inches higher then at foot one.

An oil however will not jump around negatively and positively going in the same direction on the temperature axis, say 10 cSt at 212*F, 12 cSt at 200*F, and 8 cSt at 180*F.

It may however jump un-incrementally in either a positive or negative direction, like, 10 cSt at 212*f, 12 cSt at 200*f, and 25 cSt at 180*F.

 

[fsskier]

I am glad you said these calculators are not an "exact science" but what I see is they are off by a factor of 4 . Enough to make extrapolating down to winter starting temperatures meaningless.

The GTX conventional oil turned nearly to tar, compared to the synthetic at -35C... about -31 f. Lots of the northern US sees this a couple of times each winter.

Thankfully, Denver is not 25,000 feet below sea level!!

 

[NateDN10]

Even if the GTX did have the same viscosity profile as a synthetic (and fsskier's post shows it doesn't), it would just be evidence that lots of viscosity index improvers were used. More VIIs means more shearing over time.

 

[ottotheclown]

This the highest of all the dino. Why would anyone living is a moderate cold climate ever use it??? I also noticed the Advance sale this month has the blend GTX is up to $21.99. Have fun Castrol, I wonder if they will catch on.
Originally Posted By: fsskier
Castrol Product Data sheets show:

GTX 5W30 Pumping viscosity: 40,000 at -35C
Castrol EDGE 5W30 Pumping viscosity 11,524 at -35C

The above poster is correct, the guesstimator is well beyond its accurate range.

My street elevation drops about 1 inch every 5 feet, that is accurate for the whole block. That would put Denver about 25,000 feet below sea level.....if you wished to extend the guesstimator that far....

 

[JeremyInMT]

Originally Posted By: RamFan
Originally Posted By: fsskier
Castrol Product Data sheets show:

GTX 5W30 Pumping viscosity: 40,000 at -35C
Castrol EDGE 5W30 Pumping viscosity 9900 at -35C

The above poster is correct, the guesstimator is well beyond its accurate range.

My street elevation drops about 1 inch every 5 feet, that is accurate for the whole block. That would put Denver about 25,000 feet below sea level.....if you wished to extend the guesstimator that far....


While it is true that these calculators are not exact science I think they may give a good idea of how an oil will perform.

Your elevation example is not quite the same. Elevation will go up and down, elevation at 3 feet down your block is 3 inches lower then foot one, but at 6 feet down your block it may be 2 inches higher then at foot one.

An oil however will not jump around negatively and positively going in the same direction on the temperature axis, say 10 cSt at 212*F, 12 cSt at 200*F, and 8 cSt at 180*F.

It may however jump un-incrementally in either a positive or negative direction, like, 10 cSt at 212*f, 12 cSt at 200*f, and 25 cSt at 180*F.


I get what you are saying, but fsskier's point was still completely valid. After all, all analogies fall apart at some point.

 

[SpitfireS]

The Widman calculator produces a curve, not a straight line.
As far as I understand, Widman doesn't use the 2 given points at 40C and 100C and draws a line through those 2 points all the way from -20C to 120C.