is 10w30 synthetic? and is it thinner than 5w30? thanks

 

Uh yes and no. You can get 10-30 in both dino and synthetic. As far as it being thinner than 5w-30.....No. It is just as the viscocity says. Synthetic oil is just a lil slicker and hold up better. Although some oils run a lil thinner than the specs it aint that much of a diff.

 

The first number tells you the viscosity at low temperature (startup) and the second number tells you the viscosity at high temperature (normal operating). A 5W oil is "thinner" at 0degF than a 10W oil. A 5W-30 and a 10W-30 are identical at 200degF. The same viscosity rating system is used for both conventional and synthetic oils, so you can't tell from the info you posted.

At least in theory. You will find variations from brand to brand, and you will find less consistant viscosity, over time in "conventional" oils than in synthetics.

The 5W-30 would be the preferred oil in areas that often see 0degF winter days, because it will circulate better at those low temperatures.

 

Search for posts by 'patman'. He actually performs oil analysis of his samples and knows which oils fit into which end of the viscosity range. Like anything 30wt is classified over an acceptable range and he knows which oils are at the high or low ends of those specifications and which are better.

-brent

 

So since I live in the south and we rarely see temps in the 20's I could use the 10w30 with no problems. I'm curious because my car has 118k and I have always run 5w30 but have been thinking of using a thicker oil due to the mileage on the vehicle.

 

You could still use a thicker oil even in 5w30 form though. Keep in mind the thickness is determined by it's viscosity at 100C. So both 5w30 and 10w30 will have viscosities at 100C of between 9.3cst and 12.5cst. It varies from one brand to the next, so it's possible for one brand of 5w30 to have a thicker hot viscosity than another brand of 10w30. This is why I recommend oils like Redline, Amsoil or German Castrol, since all of them are on the thicker end of the 30wt range. In some cases you might even find your high mileage engine would prefer an oil that's just in the beginning of the 40wt range (something just slightly above 12.5cst at 100C)