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Re: What do the oil designations mean? 5W-30, 10W-40, etc Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 3 Aug 2001 13:41:02
In Reply to: What do the oil designations mean? 5W-30, 10W-40, etc, Rob  [Profile/Gallery]
, Fri, 3 Aug 2001 13:03:31
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The designations determine how thick the oil is. The lower the number, the thinner the oil. You want an oil that's thin to start so it coats quickly, but thick enough when warm to provide lubrication. Since oil thins with temperature, that's a neat trick. But that's accomplished by a variety of additives.
Hot is relative - it maybe 90F outside or 60 F, but either way the oil in the engine is still running around 200-250 F. Your engine may run a few degrees warmer on a hot day than a cold day, but that won't affect the oil that much. It matters when it's really cold out. If it's 0 degrees outside, you want an oil with a lower low number, like 10-30 or 5-30. You need that low number so the oil will be thin enough in really cold temperatures to lubricate the engine until it warms up.
In the summer, you don't need to run as low a low number, because even in a 'cold' engine, you're at 60F to begin with, and the oil is a bit thinner.
In general, a real good rule of thumb is to use what it says in the manual, and to avoid big spreads in oil viscosity. 10-30 is better than 10-40, or 5-50. That's because in order to get that wide range of viscosity, many additives neeed to be added. Additives aren't bad, but they do break down over time, and you lose that wide range. So why pay for it if you don't need it, and will only lose it?
Unless you seem to be burning oil, don't go to a thicker oil. It just will be, well, thicker, and that doesn't translate into better lubrication. It's a THIN layer of oil that does the lubricating.
So - stick with the recommendations. Since it's summer, you're probably fine with a 10-30 or 10-40. I run 10-30 year round and have never had an oil related problem (knock on imitation wood grain). If your engine is burning a lot of oil, maybe running 50-20 would help a little, but it would be stop-gap at best.
, Fri, 3 Aug 2001 13:03:31, Fri, 3 Aug 2001 13:41:02 <-- Viewing This Message, Fri, 3 Aug 2001 14:17:51
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