I think you might have this a little mixed up. When cold 10W-30 and 10W-40 would act the same. Cold being during start up. Once the car is running for more then a couple of minutes Forget about the first number. It no longer means anything. Long before the motor reached 195 degs the oil is at it Primary weight.

Primary Weight of the oil should be a function of bearing cleance in the motor. If you run 10w30 in the summer and you live in a really cold place going to 5W30 for the winter would be fine. GM want you to use 5W30 year round to get the oil flowing faster. Wear due to dry drving is a big problem because people are in such a hurry. Let your car run for idle 10-20 seconds before driving it and th reason for running 5w30 goes away.

 

ahhh ok. So is there anything wrong with using 10w-40 ??? I have always used 5w-30 year round.

 

no not if the motor is having oil pressure problems. my pressure is at 40 to 60 so 10w40 would put it higher and allow less oil to flow. not a good thing. now if my pressure was 5 to 20 then i would look at switching to 10w40. which i did with my last camaro. ended up switching oil pump to high volume which brought it up to 20 to 40

 

yeah i agree with you there Castrol is better for me.

 

I ran Castrol most of my younger life. Infact I ran it right up till the day I had to do a head gaskets on a fleet truck with a 150K on it. The company had a big sign under the hood. "Mobil 1 only!" When I pulled the head off I did not have to clean the valve cover area. I just wiped it with a paper towel. I could see the gray cast iron like is was a brand new head. I never had that will my own cars and I did oil changed every 2000 miles. I have used Mobil 1 is every car I cared about since.

 

I didn't know there was an oil other than Mobil 1.
I run it in my LT1 Vette. With 108k miles, the heads are still as clean as a whistle under the valve covers. I have no reason nor desire to use the cheap oils. Besides, using synthetic motor oil costs less.

 

I run full synthetic in everything I own. I can usually find a full synth on sale for around $25/gallon if I look around a bit. I would love to run Mobil 1 in everything, but it NEVER seems to go on sale. If I found it at that price point I would buy a pile!

10w30 in the Camaro, 5W30 in the DD's. Camaro is parked for the winter months, rarely gets started, and when it does, it's in the warm shop when it starts.

I have a buddy who works for an oil sampling company, and he tells me that even when your oil is filthy, it still far exceeds the OEM specs required by the dealer. Having said that, I still change the oil far too often in everything I drive. Small piece of mind I guess.

 

Mobil1 5 quart bottle, $24.97 at Walmart. It used to be $22 last year. Oil must be more expensive up dare by you, ya?

 

EVERYTHING is more expensive up here. You should see how they rape us on beer prices....

I shop in Michigan a lot for stuff like this. Depending on the border guard you get, sometimes you pay duty and taxes, sometimes not...

 

Oh man. The oil is bad enough, but not the beer!!!!