I just had my oil changed and realized that they used 5W30 instead of 10W30 like the manual recommends. When I called the dealership, they said that Honda recently switched there recommendation to 5W-30 for all their cars. I said that the S2K manual calls for 10-30 he said he would have to call the tech line.

Has anyone heard of this? Should I have them switch it back to 10-30 or does it really matter?

 

In some documentation you will find a 5W30 recommendation. It doesn't really matter.

I will only use 5W30 in mine.. it is thinner when cold and is pumped through the engine faster on startup.

 

How could 5W30 be thinner cold than 10W30? Both are 30 weight when cold aren't they? I thought oil viscosity got thinner as the temp rises. Wouldn't 5W be thinner at operating temp than 10W? Help! I'm so confused!

 

Depends on the temperature. Scale from freezing?? to boiling point??, but don't quote me on the rages. Your right about the scales, but since most of us don't start our cars at 0deg C.

 

You know, anymore it is pretty hard to make generalizations about motor oils, so I had to go look up the specs to be sure I even had an answer. And I don

 

OK, I've been corrected by my mechanic officemate. 5W30 means that the weight of the oil at room temperature is 5 and the equivilant lubrication of 30 at operating temperature. Counter-intuitive. It is because of some polymer additives in the oil that expand under heat.

 

I have never seen any Honda information saying it's o.k. to use 5-30. Where does this come from? Just curious, sounds reasonable to use, esp for winter months in some areas...

 

bjl, if you live in SoCal, I wouldn't worry about it. Just get it changed back to 10W30 at your next oil change.

 

Hmm, Mobil 1 info that came with my oil was that it was brill at Arctic Temps and Brill at Desert Temps. I thought that was okay for me so I use the 0-40W synthetic Mobil 1. My UK dealer was happy putting that in as they now use synthetic shell Helix 0-40W as their preferred oil.

 

QUOTE:

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.
Multi viscosity oils are one of the great improvements in oils, but they should be chosen wisely. Always use a multi grade with the narrowest span of viscosity that is appropriate for the temperatures you are going to encounter. In the winter base your decision on the lowest temperature you will encounter, in the summer, the highest temperature you expect. The polymers can shear and burn forming deposits that can cause ring sticking and other problems. 10W-40 and 5W-30 require a lot of polymers (synthetics excluded) to achieve that range. This has caused problems in diesel engines, but fewer polymers are better for all engines. The wide viscosity range oils, in general, are more prone to viscosity and thermal breakdown due to the high polymer content. It is the oil that lubricates, not the additives. Oils that can do their job with the fewest additives are the best.

Very few manufactures recommend 10W-40 any more, and some threaten to void warranties if it is used. It was not included in this article for that reason. 20W-50 is the same 30 point spread, but because it starts with a heavier base it requires less viscosity index improvers (polymers) to do the job. AMSOIL can formulate their 10W-30 and 15W-40 with no viscosity index improvers but uses some in the 10W-40 and 5W-30. Mobil 1 uses no viscosity improvers in their 5W-30, and I assume the new 10W-30. Follow your manufacturer's recommendations as to which weights are appropriate for your vehicle.