OIl Viscosity Question

[nimith]

Now that winter is over in Wisconsin, my friend switches his oil to 10w-40. I use the 5w-30 synthetic year-round. I told him with only 40,000 on his car, the oil may not flow proper in tight places. I have to admit though, his car sounds a lot more silent. Any thoughts-thanks!

[06vitzRS]

Put in what ever the owners manual says. (I don't know why everyone insists on dicking with there oil.)

[PolarWhite]

Please, when will we ever outgrow this old school thinking? You NEVER EVER put anything in your car except what is written in the manual or on the oil cap. Some manuals even state that using other weights such as 10/40 or 20/50 will void the warranty. No where in your manual or any other vehicle manual does it say that the weight of oil depends on whether it is winter or summer. That is old school crap that your grandpa told you. Motor oil and engines of today do not even resemble the engines of yester year. You don't need a think gunky oil to fill in the gaps in the engine. Please tell him to stick to the correct oil. He is also hurting his gas mileage because 10/40 is not energy conserving.

[jdinrc]

Please, when will we ever outgrow this old school thinking? You NEVER EVER put anything in your car except what is written in the manual or on the oil cap. Some manuals even state that using other weights such as 10/40 or 20/50 will void the warranty. No where in your manual or any other vehicle manual does it say that the weight of oil depends on whether it is winter or summer. That is old school crap that your grandpa told you. Motor oil and engines of today do not even resemble the engines of yester year. You don't need a think gunky oil to fill in the gaps in the engine. Please tell him to stick to the correct oil. He is also hurting his gas mileage because 10/40 is not energy conserving.

+1 :thumbsup:

Back before multi-grade motor oil blends, the single weight oils would need to be changed by season as 40W was too think for cold winters, but the engines needed that heavy oil in the summer so it wouldn't break down so easliy in the heat. That simply isn't the case anymore, and the OEM's have done extensive research with the oil companies (that they didn't bother with in ye olden days) to find the best blends to work with their engines.