Japan not too happy with GF-4 Oils ?

[ym42]

I had recently replaced a timing belt on my Corolla 96, 200 000 miles on the engine, and it was not nearly as difficult as I imagined. I could do it again in about an hour, if I had too. The most stupid part of it is that you need to take the valve train cover off to change the belt, not just the belt cover, but it really was not too bad. I have yet to see how hard it is to change the chain in my Saturn.

 

[Ray H]

quote:

---

Originally posted by ericgl:
...Funny, I thought the Japanese used timing belts.

---

Nissan, Toyota, and Honda are known to use chains in their newer engine designs. Chains are hard on motor oil - lotsa shear moments on those little oil molecule guys. Sheared molecules lose lubricity and film strength, and contribute to sludge formation due to free radicals' affinity for oxydizing in unpredictable ways. Note to paO4prius: Chains are NOT necessarily more reliable than belts in all applications, either. And, chains are definitely noisier than belts. (Given that most OHC designs - belt or chain - require extensive labor to reach the water pump, replacing a belt at the same time adds little to the final bill since the labor charge eats up the lion's share of the total. Like it or not, for most owners, their cars are gonna require $500.00 - $600.00 {or more, adjusted for inflation} professional service every 60,000 - 80,000 miles regardless what type of timing drive is employed.)

Finally, the Japanese have been known to be concerned about oil breakdown in engines using timing chains for some time. This is NOT an issue specifically about GF-4 as several have mistakenly inferred - the Japanese companies were concerned about chain shear with GF-2 and GF-3 oils, too. With more Japanese motors now going to timing chains, though, the issue's coming to a head. If ILSAC and API can't deal with this to the Japanese manufacturers' satisfaction, don't be surprised to see Japanese (and perhaps Korean?) auto companies do just what their European counterparts have done - specify their own proprietary lubrication requirements (which may obviate the use of generally available oils in the retail market) in order for their owners to maintain their powertrain warranty as it applies to engines. GM at one point threatened just such a move during the negotiations for "SM"/"GF-4" over another matter, but eventually came on board with the majority. Nevertheless, that threat leaves open an eventual free-for-all regarding motor oil standards - if not with GF-5, probably by the time an eventual GF-6 standard comes up for consideration - in which each company, foreign and domestic, does what Mercedes Benz, BMW, Porsche, and VW-Audi already do to some extent. Start likin' it.

 

[1sttruck]

...too many variables spoil the talk... assume that for any considered oil the additive pac is the same and that for any one graph the temperature is given. Then imagine maybe wear plotted in 'chain load space' (low vs high sustained load or low vs high, rapidly applied load) vs 'oil viscosity space'. The load may need to be simplified as the types of wear will probably be different. Anyway, in this 'space' one would assume that a heavier oil will provide lower wear. Different additive pacs will tend to translate all of the oil weights, and one would assume that lots of traditional anti-wear additives will minimize wear. Higher temperatures will tend to produce wear as the oil thins.

Per a discussion in the motorcycle forum it seems that a common bench test that might be applicable in this situation is the 4 ball, where a gear oil would do well minimze chain and sprocket wear.

 

[lkchris]

quote:

---

Originally posted by Jay:
The biggest advantage of belts is that they don't lengthen as they wear as chains do

---

Biggest advantage of belts is economics of production. Belt is cheaper and the engine designer does not have to provide oiling as s/he does for the chain.

 

[MillerMan]

what about chyslers 2.7 V6, used in dodge stratus, sebring, dodge intrepid etc from about 2001 and newer.

I hear the timing chains and guides go out, big bucks to fix. is it a poor design or a oil problem?

anybody esle hear about this problem in the 2.7 V6?

 

[1911]

[You can reason that since a timeing chian is constantly rubing against a sprocket that it is a high shear zone! Any high shear zone is going to be affected by HTHS or a lack of it! While a chain is not as bad as gears on gears or a flat tapet etc... it is still a high shear area. I would also point out that few OEM chains are what we would call a roller chain. [/QB][/QUOTE]

No disrespect to you JB since you are the inventor of me (the 1911) but a roller chain is not a good place to apply HTHS terminology. HTHS should properly be referred to as HTHSR meaning High Temperature High Shear Rate as that is what the test is all about.....the shear rate, not the shear load!! In fact the real name of the test is high temperature high shear rate. Oil is not a perfectly Newtonian fluid and therefore apparent viscosity is shear rate dependent......yes that is the whole purpose of the test. The missing R clearly has many here confused for sure. It does not refer to high shear but high shear rate!!!! This concept of non Newtonian shear rate dependent behaviour on effective viscosity is emphasized heavily in the study of fluid behaviour in enginerering classes. It applied to airplane wings and everything else where the shear rate can be high.

You're right in that roller chains generally do need high vis lubricants if they are highly loaded. This is simply due to one reason, the rate of articulation. Roller chains wear when they articulate and in an engineering book, this refers to the relative rotational motion of one link relative to another as they go both enter and leave the loaded line of the chain. (When links are on the back of the sprockets and the return trip, they are essentially unloaded). A the chain articulates, it is now a bearing (under load with surfaces turning relative to other mating contact surfaces). The angle that one link rotates relative to another is called the angle of articulation and is contolled by the sprocket size and the chain pitch.

Now sometime back we had a little lesson here about the fundamentals of lubrication where we discussed aquaplaning. We discussed how low RPM's always make it more difficult to form an oil film and how RPM was even more significant than load itself mathematically in determining oil film thickness!!!! Well, basically, the angular velocity of the articulating links is rather low on a typical roller chain but perhaps much higher in a car engine than many other industrial applications. We used to have to use strong EP type lubes in slow roller chain applications when I worked in the paper industry.

1911

 

[1sttruck]

Of the common gear and motor oils available at a corner auto store, I'd guess that Mobil 1 75w90 would do well to minimize chain wear, 75w140 for sustained high loads, but these don't seem to make good engine oils. I'll guess that a heavier synthetic HDEO like Delvac would fare well, and that one of the worst oils that you could choose would be a 5w20 dino with wimpy additives.

 

[1911]

Hey Guys,

One more point about High Temperature High Shear Rate (HTHS) tests. The results are used in reference or comparison to the application of high speed bearings where the shear rate is high. The test is not very applicable to gears/roller chains/etc or other applications where boundary or other types of lubrication may be dominant. It is a high lubricant temperature, high shear rate test...... not a high lubricant temperature, high shear test.

1911