Join Date: Jun 2001
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Re: Engine oil question.....
5W-30 is probably your best bet. 10W-30 and 5W-30 are close to the same viscosity (sp?) at operating temp, but 5W-30 is thinner when cold - which means it flows much quicker. Yes, it's like water, but it's supposed to be like water and there is a good reason for it - It flows quick cold, minimizing the time the critical moving parts are running dry.
The second number is what's most important - it will determine oil pressure at operating temp and the rate at which the oil flows. The Zuki engine is designed to run with either 10W-30 or 5W-30, and anything thicker at operating temp (ie: 10W-40, 15W-40, 20W-50) is bad for it and may ultimately shorten the life of the engine and reduce performance.
Remember, oil pressure is created by the resistance of the oil being forced through bearings and other passages. Thicker oil will raise pressure, but it's also substantially reducing the flow rate - since less oil is forced throught the same size opening. Higher pressure isn't always better - it's flow rate your really concerned about.
You can have 10 PSI at idle, and have enought flow for everything to be AOK (the reduced pressure is caused be wear, opening up the tolorances and reducing backpressure - but the oil is still flowing - and that's what REALLY matters.)
You can also have 50 PSI in the same engine at idle (by running much thicker oil) and not have enough flow to properly lubricate and cool the vital parts of the engine.
Sorry, got a little carried away with that reply [img]images/graemlins/wink.gif[/img]
But, to answer your question, switching from 5W-30 to 10W-30 will not stop leaks or increase pressure (since it's approximately the same viscosity at operating temp).
What it will do, however, is increase the time that the lifters/cam bearings/etc. run dry when the engine is first started.
IMHO, I would stick with the 5W-30.
I run Mobil 1 0W-30 in my Sidekick year round. There was a noticable deference in how quick the engine starts up and stabilizes when I switched from the 5W-30.