Tuesday, Feb 03, 2009 at 14:45
On the LCOOL site this guy posted some information about the replies here.
Sounds as if he knows a fair bit about this.
The guy responded with the following.
The GTX2 has the correct amount of detergent to clean oilways in conjunction with genuine Toyota filters makes all the difference, I am a Mechanical Engineer with more than 50 years involved within this industry, occasionally you pick up a tip that works & this is one of them, usually caused by non genuine filters, this process can be done once a year or once every whenever - a cheap & rewarding pat on the back for your engine. As I stated before after this process go to the oil of your choice - whatever works for you. "
He does know what he is talking about
Regards
I would agree with his solution, but I do not agree with his reasoning.
What the problem is has nothing to do with engine oil detergency.
It does have a lot to do with viscosity and viscosity stability of the engine oil, hydraulic pressure retention in the followers, as
well as the anti-drain back valve in the filter.
In service, multigrade engine oils undergo shearing of the polymer content [the additive that renders the oil its multigrade properties], such that they lose their viscosity over time. Apart from fuel dilution in service that is the reason why used oils appear "thin" when drained and left to cool to room temperature.
Oil filters play an important role in retaining a supply of oil "ready" to circulate when an engine is cranked. They contain a valve that prevents oil from completely draining from them on standing.
If the valve does not work effectively [many non genuine filters have poor performance in preventing draining on standing, some do not even have a valve at all (lower cost)] and after the engine oil has been sheared in service there is a reduced supply of oil from the filter to the top end of the motor during cranking and the followers are not hydraulically primed sufficient to prevent tappet noise.
Most engines take between 30 seconds and 5 minutes for a full supply of oil at pressure to reach all through the top of the motor, and while many engines need very little pressure at idle the attendant tappet noise in a properly maintained engine usually indicates a lack of hydraulic pressure in one or more followers.
Now followers themselves can be a culprit here as they sometimes “leak down” on standing, but this is usually not a widespread problem in modern engines. The lack of oil supply on starting cranking is a more common fault, per above.
The reason Castrol GTX 2 is one of the many fixes, is because it is relatively high in viscosity at ambient temperature, being a 20W-50, and because it has very good shear stability [i.e.: its polymer resists mechanical shear in the engine]. It therefore retains its viscosity in service and does not drain from the filter/followers as much as lower viscosity and less shear stable engine oils. This is particularly relevant as the engine oil begins to reach the end of its drain interval. In fact some oils may be “quiet regarding tappet noise on start-up when new” but develop the ‘noise’ after 5,000km service. This points to a loss of viscosity as above.
There are other properly formulated SAE 15W-40 engine oils with excellent shear stability, as
well as some SAE 10W-30 Energy Conserving engine oils that are suitable alternatives to Castrol GTX2.
As
well a genuine Toyota oil filter will retain the oil on standing so the engine benefits from adequate supply on start up.
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