5W-30 For Temperatures only below 60F?

[GSUjinih]

So I as considering changing my oil in my 1994 Q45 to 5W-30 to help out with the colder mornings here. I looked at the owner's manual and it mentioned that 5W-30 should only be used for temperatures below 60F? I figured that this was just maybe something they did in the early/mid 90's. I checked my 240SX and it said that 5W-30 can be used for all temperatures. Why did they not recommend 5W-30 for higher temperatures? Also some very cold mornings (near freezing) I heard a light tapping noise from the engine, but seems to go away when warmed up. Is that the HLAs? Will going to a thinner oil improve that noise?

[GSUjinih]

Still curious for a response why Nissan does not recommend 5w-30 for higher outside temps?

[bruce2]

I don't think thinner oil will improve in the noise. However to ease your concern, you might like to try synthetic. From the collective wisdom in the web, the main benefit of synthetic is faster lubrication during cold starts so less wear and tear on the engine since most engine wear occurs at start up. I have been using Mobil 1 5W30 full syn in all vehicles in my household including the Q for years and no complain.

[djwarner]

Wouldn't this be a summer issue? The low temperature number is 5W and the high temperature number is 30W. The low temperature number is only significant on start-up before the engine comes up to operating temperature. 5W is thinner than 30W at these temperatures making it easier to turn the engine over when cold.

Once the engine warms up, the oil acts like straight 30W oil.

Cold 5W is still thicker than 30W at normal operating temperature. So even this oil thins out as it warms.

My 2002 Q45 uses 5W-30 all year round. For those of you in cold country, Mobil 1 has a 0W-30 that I would recommend to reduce battery strain on cold start.

[Q451990]

For an explanation of motor oil - there's no better one I've seen than this. Brew up a pot of coffee and take some time to read this. http://www.bobistheoilguy.com/motor-oil-101/

I'm sure there's some opinion in there, but this guy's opinions are based on more oil science and knowledge than I'll ever learn, so I'm going with it. Cliff notes - The first number refers to cold performance, and the second number refers to performance at normal operating temperature. The lower the first number, the faster the oil will behave like it's at normal operating temperature. I switched from M1 5W-30 in the G and M1 10W-30 in the Q to M1 0W-30 in both cars a couple of years ago.

Keep in mind that Nissan specified oils based on what was commonly available at the time the car was built (and to some extent what was easily available in big drums to their dealer network). By 1996 the owner's manual showed 5W-30 as the preferred oil at all temperatures, and 10W-30 as OK above 0F. As far as I know the bottom of the engine is identical to the 90-95Q.

Heath

[GSUjinih]

However in 1996 they dropped the variable valve timing. I have not looked into how this works exactly, but if oil-actuated this could be one of the reasons why they switched in 1996.

[Q451990]

The 1995 Owner's manual shows the same thing as the 1996, so I don't think the change was VVT related - although it is oil actuated. There's a gap of available owners manuals on the site, so the next earliest one was the 1992 manual, which shows 5w-30 for ambient temperatures of 60F and below, and 10w-30 for ambient temperatures of 0F and above.

Heath

[GSUjinih]

I have the original owner's manual for 1994 and it has the same specifications you mentioned for the 1992 model. Very strange that they changed this.