I've been using Mobile1 5w30 on my rex for the past 18k miles. However, my last visit at Costco, they ran out of 5w30, so I bougth some 10w30. Are there any downsides to the switch? The switch is going to be temporary only for about 3-6k. I know that switching from dino oil to synthetic and back can be harmfulll for the engine, but I'm not sure on switching the viscocity. Thanks for the responses.

 

Should be ok. People who live in states where it gets extremely cold probably switch their viscosity seasonally.



:banana:

 

k. thanks.

 

I run 5-30 during snowboarding season and 10-30 all other times of the year.

 

I'm also in the Bay Area, I wouldn't have to worry about anything freezing right? Is 5w30 for freezing temps?

 

There's a graph in your owner's manual which shows the temperature range of various oils. Basically, the first number (a 5 or 10) is the weight of the oil when cold and the second number (30) is the weight when warmed up. In general, the smaller the difference between the two numbers, the more stable the oil is.

 

5w30 should be ok.


:banana:

 

in the bay area 5w-30 or 10w-30 will work just fine.

the only difference is that 10w-30 is a little bit thicker. how does this effect things? during colder weather its harder to get the oil moving during a cold start up. but it doesnt' ever get cold enough here to have any issues.

 

In the bay area you can run a straight weight oil, such as SAE30, of SAE40. It's even listed in the manual.

 

I put in an oil pressure gauge last spring and on 5w30 in the summer it never goes above 90psi at startup. But now in the winter the gauge gets pinned (100psi meter) which makes me wonder if I should get 0W30 for the winter.

 

oil pressure is determined by the pressure release spring, at the end of the day oil viscosity should not effect oil pressure with a fully functioning pump since the pump is supposed to be able to outlfow the motors demand and maintain pressure, therefore the only way to change oil pressure on a fully functional system should be to change the oil pressure release spring.

therefore any change in pressure is due to other factors, and not oil viscosity.

 

that is true. i have run sae30 in my wrx in the past and usually during the summer months i would actually run 15w-50

 

i run 10w30 all year long

 

Then why is oil pressure higher in a cool engine than in a warm engine? I thought it was because it was going from 5W to 30, but its not?