Why use thicker oil?

[Steve S]

Originally Posted By: Doug Hillary
Hi,
Steve S - It is not the bulk oil temperature that is so critical. It is the operating areas of the engine that depend on the lubricant to cool and lubricate. Some areas easily see around 175-200C outside of the "fire zone" and this is especially so with charged engines - the return to bulk oil temperatures tell some of the story

In these cases the minimum HTHS requirement is detemined by such things, as the component operating temperatues may be 100C or more abouve the bulk oil temperature. Wear can occur through the loss of the lubricant's film (viscosity) to a point that boundary lubrication is the only means left - at this point the destructive minor contaminants do their nasty tasks
I know.Still the higher the load or power output the higher the heat in general.

 

[Doug Hillary]

Hi,
Steve S - In principle you are correct although there is usually a designed maximum bulk oil temperature for durability purposes

This is a design factor and often the engine as you know will include oil coolers/intercoolers and the like aligned with a suitable sump size. Typically where an engine is designed for a synthetic lubricant this can be as high as >130C. In the case of Porsche this is usually around 120C. Most heavy high speed diesel engines have a "power down" controller (oil temps at around 115C) in the ECM

However it is very common to see much much higher lubricant return temperatures than the above - and this is normal

This was an issue with many VW installations in the 1990s where poor airflow caused excessively high oil temps and engine failures (especially with mineral lubricants). Some Porsche engines had the same problems. Individual components were really overheated but the bulk oil temepratures were not "excessive" by today's standards

 

[Steve S]

Years ago 1986 I had an aquaintence who had 1976 Porsche 930 turbo ,the one with the whale tail spoiler ,flaired wheel wells and big tires.I would have to say a most impressive car . WOT would throw you back in the seat, something really special in a 1976 car any way you could putt around all day with out any excessive heat ,put your foot to the floor till the wastegate opened , hold it there then there would be instant heat.Too bad he eventually rolled the car!

 

[vinu_neuro]

Why are the upcoming M1 race oils only available in 0W-20 and 0W-30?

 

[Doug Hillary]

Hi,
Steve S - Yes the turbo is just one factor and you got it right with that model

Most German cars seem to have their designed minimum bulk oil temperatue at around 89C-98C and the maximum as stated earlier. In some ways if the bulk oil temperature is too cool in normal operating conditions, optimal efficiency is never reached

 

[Doug Hillary]

Hi,
I suspect they have done their research and that is what is called for. They are just that of course - race oils and the F1 experience would have assisted in the final formulations

Porsche use M1 0W-40 in their modern race cars and 15W-40 and 20W-50 in the Classics from the 1950s-1980s - I'll be in Zuffenhausen in April and I'll ask the Engineers running their race cars if they are "heading south" too!

 

[Steve S]

That is what modern engines are designed to use. Nascar engines are run with some kind of 30 wt and oil coolers etc. Todays oils are not 1960 oils.

 

[Steve S]

Originally Posted By: Doug Hillary
Hi,
I suspect they have done their research and that is what is called for. They are just that of course - race oils and the F1 experience would have assisted in the final formulations

Porsche use M1 0W-40 in their modern race cars and 15W-40 and 20W-50 in the Classics from the 1950s-1980s - I'll be in Zuffenhausen in April and I'll ask the Engineers running their race cars if they are "heading south" too!

0w-20 across their whole product line

 

[vinu_neuro]

That's what I was alluding too. With all the discussion of more viscous oils being better, one has to wonder if that's really the case even in race conditions. I wonder what weights oils are used in the really long endurance races.

Originally Posted By: Steve S
That is what modern engines are designed to use. Nascar engines are run with some kind of 30 wt and oil coolers etc. Todays oils are not 1960 oils.

 

[vxcalais]

Originally Posted By: vinu_neuro
That's what I was alluding too. With all the discussion of more viscous oils being better, one has to wonder if that's really the case even in race conditions. I wonder what weights oils are used in the really long endurance races.

Originally Posted By: Steve S
That is what modern engines are designed to use. Nascar engines are run with some kind of 30 wt and oil coolers etc. Todays oils are not 1960 oils.


http://www.shell-racing.com.au/products.html

According to Shell it could be anything from a 0W20, 0W40 (Rally) or 10W60.

 

[1sttruck]

People use thicker oil to try to manage wear, but whether they're successful or not is hard to tell. Ferrari and Shell did the same in F1 when they had to make engines last, so they'd use a thicker oil in practice for less wear and a thinner oil for racing for better performance. Europe has had higher fuel costs for decades but they're largely resisted using thinner oils for the very small / unmeasurable benefit in increased fuel mileage, as vehicles may end up being used at sustained high speeds where a thicker oil could be warranted. The longer oil change intervals seem to play a role too. Outside the US it's evidently still common to see different grades of oil being recommended for different temperature ranges.

If you're on the edge of some sort of performance cliff, where thinner or thicker is called for, then using thinner or thicker makes sense. The trick is determining where that is.

 

[Seth]

Just run two UOAs with thinner and thicker oils on same vehicle and compare the results. Should be easy to see which one did better.. Oh and it has to be in the same season (winter over winter or summer over summer) and the car should not be new vehicle to keep the comparo more accurate.

 

[FrankN4]

Originally Posted By: Doug Hillary
Hi,
Steve S - It is not the bulk oil temperature that is so critical. It is the operating areas of the engine that depend on the lubricant to cool and lubricate. Some areas easily see around 175-200C outside of the "fire zone" and this is especially so with charged engines - the return to bulk oil temperatures tell some of the story

In these cases the minimum HTHS requirement is detemined by such things, as the component operating temperatues may be 100C or more abouve the bulk oil temperature. Wear can occur through the loss of the lubricant's film (viscosity) to a point that boundary lubrication is the only means left - at this point the destructive minor contaminants do their nasty tasks


First let me say that I don't know a lot about 30 grade oils as I have never used them in my personal cars. I have had some "company cars" that were maintained by contract that used 30 grade conventional and I did not like it.

I used a single 40 grade(not XW-40) from 1960 to 1968. I used Castrol conventional 20W-50 from 1968 to 1988. I used Castrol Syntec 5W-50 from 1988 to 1990. I have used Mobil 1 15W-50 since 1990, in everything.

Now that we know my experience with 30 grade, a question.
10W-30 no. 1, GP IV, has a HTHS of 3.26 but a 100C cSt of 12.44.
10W-30 no. 2, GP III, has a HTHS of 3.5 but a 100C cSt of 11.2.
OCI would be 3000 and NEVER exceed 3500 miles.
Which would actually protect the engine if bulk oil temp never exceeded 230F? I have no clue what high point temperatures might be. (I have always considered bulk oil temp of 230, crossing mts with camper pack, far beyond the scope of a 30 grade)

 

[BuickGN]

Originally Posted By: FrankN4


Now that we know my experience with 30 grade, a question.
10W-30 no. 1, GP IV, has a HTHS of 3.26 but a 100C cSt of 12.44.
10W-30 no. 2, GP III, has a HTHS of 3.5 but a 100C cSt of 11.2.
OCI would be 3000 and NEVER exceed 3500 miles.
Which would actually protect the engine if bulk oil temp never exceeded 230F? I have no clue what high point temperatures might be. (I have always considered bulk oil temp of 230, crossing mts with camper pack, far beyond the scope of a 30 grade)



Very good question. I'm curious also.

 

[CATERHAM]

What GP III 10W-30 has a HTHS vis as high as 3.5?

 

[FrankN4]

Originally Posted By: CATERHAM
What GP III 10W-30 has a HTHS vis as high as 3.5?


Valvolin full synthetic MaxLife has a HTHS of 3.56 and meets ACEA A3.

 

[Gary Allan]

Quote:
Which would actually protect the engine if bulk oil temp never exceeded 230F? I have no clue what high point temperatures might be. (I have always considered bulk oil temp of 230, crossing mts with camper pack, far beyond the scope of a 30 grade)


How about both? What you're really asking, Frank, is which oil will have more marginal reserve at higher oil temps. It would be just that, marginal. The effects would be more along the lines of how long you could keep it in service. Oil fatigues on a time weighted average (at temp) too, just like ATF ..but with other, more complex, influences included.

Oils appear more alike as they heat.

 

[FrankN4]

OK Gary. Does that really mean that with my short OCI, the fact that I only use, synthetic oils, I might want to be more concerned about a comet hitting the North Pole?

I don't have an oil temp gauge on the Silverado(yet) but the Toyota pickup would run everday bulk temps of 195-218F. Crossing the Smokey Mts with a full load and pulling a trailer, it would go slightly over 230, maybe 232. On a non existent average 3000 mile OCI, the bulk oil temp would be above 218, up to 232, no more than 60 of those miles. Is it the extra high tempeatures, under load, around the pistons/rings, cyl walls that bring up the bulk temperature? Is this where the higher HTHS number comes into play?

If the HTHS number is higher, does that mean I am going to have more real protection, a better oil film, at the higher oil temperatures? What I am trying to ask is will a HTHS of 3.5 give somewhat more protection at the high temperature points than a HTHS of 3.2, or will it give same protection but protect longer?

Feel free to respond in any you think my mind can handle it.

 

[JAG]

The oil film thickness in journal bearings at full operating temperature has been found to correlate reasonably well with HTHS viscosity. There are many caveats, however, and I can't name them all. One of them is that bearing wear has been found to be so dependent on the oils' detergent/dispersant additive package that some thinner oils with better deterg./dispers. add. packages show less bearing wear than some thicker ones with lesser said additive packages.

The answer to your "protection" question is that it is impossible to predict wear protection from just the information you provided about the oils. Their are too many other oil-related variables beyond virgin HTHS and kinematic viscosities.

All this and more is right here, written by industry experts: http://books.google.com/books?id=Fu-99Mc...result#PPA45,M1

Yes as you increase the load on the engine, more heat is transferred to the engine and oil from the hotter combustion chambers and that's the main reason why the oil temperature went up.

 

[Gary Allan]

JAG to the rescue!

Under most conditions, oil temp is a product of combustion impulses/min ..indexed against any natural rejection rate (non-forced cooling scenarios).

I don't see the temps mentioned being anything outside of the anticipated process variable. The higher specific output of the engine will dictate the ultimate fatigue rate in some time weighted average manner.