Hugh said:
Zenky said:
The following is important
One point that no one brought up however is the difference between synthetics and conventional motor oils. Conventional oils require a lot of polymers. This really isn't a problem for gasoline engines but has caused problems in diesels. Polymers can shear and burn forming deposits that can cause ring sticking and other problems. Generally the higher base multi-viscosity oils require fewer polymers than the lower ones.
(20W50 requires fewer polymers than 10W40 even though they both have a 30 point spread.
This all becomes moot with synthetics
Synthetics require far fewer polymers to achieve their rated temperature range. In fact Mobil 1 5W30 does not use any viscosity index improvers (polymers) in their 5W-30 formulation.
So to reiterate, the thread starter has zero, I repeat zero, risk of damage to his engine by using 5W30 oil. If he were driving a diesel, I'd suggest that he make sure he is using a synthetic oil but as we all know that isn't the case.
Hugh, you hit the nail on the head. Unfortunately, you failed to drive it home.
Ken can never be wrong quoting the manual. That is incontrovertible. However, where he is mistaken is that deviating from the manual one iota is 100% wrong. Ken is a great contributor and source of information, but in this regard,
that is, in my opinion, nonsense. Here is why I think so.
When the NSX was designed in the late 1980s, synthetic oils were not common. If they were common, then the manual - which was written at the same time and has not been significantly updated except to deal with minor changes, certainly not this issue - might have been written differently. In fact, I suspect that Honda would have specified only synthetic oil for the NSX. That is what many manufacturers specified for cars introduced after the NSX.
The issue is not with the oil viscosity once the engine is at operating temperature, but at start up. In other words will 5W provide adequate protection on startup? Or will only 10W do the job?
It depends on the oil.
The shear strength of synthetic oils is far superior to that of dino oils. That means the oil is more resistant to being 'torn apart' resulting in two metal surfaces (piston rings on cylinder walls, for example) rubbing together and slowly destroying each other. Because of their higher shear strength, synthetic oils provide excellent engine protection at lower weights. That is why we see 0W synthetic oils being used. Dino oils are not made below 5W and even then 5W is intended to be used only in cold temperatures for short periods of time (even in Canada, winter hardly lasts more than six or seven months :biggrin: ). But due to its high shear strength, a synthetic 5W oil will provide excellent protection on start up. Once warmed up, the visclosity increases until it is eventually at 30, which is what the factory recommends.
With that in mind, let me pose a few questions:
Will driving 15 hours across Texas with 5W-30 in the crankcase cause engine damage? No, and I would not give it a second thought, regardless of whether it was dino or synthetic oil.
But I would be very careful about warming up and accelerate gently until it was fully warmed up. And remember the coolant temperature increases far quicker than the oil temperature. So give your engine another 5 or 10 minutes
after the temperature gauge indicates it is at operating temperature.
Would I run 5W-30 oil if I lived in Dallas? Not if I was using dino oil. But if I was using synthetic, definitely. I use 5W-30 synthetic (Redline now,and previously Mobil 1) year 'round, including four to six track days a year. Am I causing engine damage? I won't know the definitive answer until my engine gets rebuilt (presently scheduled at 300k kilometres) but I do know that my car does not burn a drop of oil between changes every 6k kilometres.
Would I insist the dealer change the oil to 10W-30? No, but I would definitely point it out, and suggest they provide the next oil change (at least the labour) for free.
Since the 5W versus 10W dead horse has been kicked around the block, maybe we should now consider
why the factory does not recommend anything higher than 30?:biggrin:
