TheStef

Hi guys,

I just bought some synthetic Mobil 1 oil, but the store only had 15w-30 left.

What's the big deal with 5w-30, 10w-30 and 15w-30 oil? does it really make a difference.

Thanks!

1stC3Vette

The oil viscosity rating is used to measure the oils resistance to flow. The lower the number, the easier the oil flows. The "W" stands for winter.

The number prior to the W shows the flow rate at a cold temperature. The number after the W shows the flow rate at operating temperature. With the oils you listed, the 5W-30 would flow the easiest at cold temperature.

Good luck,
Dino

rws.1

The first number indicates what the viscosity is when the oil is cold.
The second number indicates what the visosity is when the oil is hot.

The lower the first number the lighter the weight of the oil and the easier it flows to the extremities of the engine.

Old thinking was you needed 15 W40 or 20W50 for racing because it had higher lubricant film strength.
The new thinking is you want 0W30 for racing as the oil flows easier, lubricates quicker and helps maximize horsepower.

For summer use, you will be fine with a 15W30, especially in a higher mileage engine. If you had a newly re-built engine, i would want a lighter weight oil

Corvette0096

Just change the stuff every 3k and you will be fine. I run 15-50 Mobil one in mine..The engine builder told me to. 4k on the motor I should ad that the stock eliminator guys run "0" weight in there cars.

TheStef

Engine was rebuilt only 4 years ago, and I haven't put a lot of millage on it.

Maybe I'll bring it back and get some 10w-30 instead.

Thanks for the good info guys

bogus

It's like this... engines are built to much tighter tolerances these days. As such, a thicker oil may not get everywhere it needs to when the engine is cold.

I ran into a know-it-all at Sebring last year... he just bought a new Mitsubishi Evo 8. His first order of business? swapping out the specified 0-30 for 20-50. I said to him that's fine if you want to blow up the engine... however, because he works on race team he knows more... tool.

An engine requiring 0-30 (or, 5-30) will not always get along well with thicker oils. The journals and passages will not allow the oil to flow properly. And the 50 wt at the top end is uber-thick.

If you wanted a touch more summer protection, I would run 10-40.

But even then, it isn't required. The oil will not break down anyway.

stevec4

A more detailed explanation might be

Multi viscosity oils work like this: Polymers are added to a light base (5W, 10W, 20W), which prevent the oil from thinning as much as it warms up. At cold temperatures the polymers are coiled up and allow the oil to flow as their low numbers indicate. As the oil warms up the polymers begin to unwind into long chains that prevent the oil from thinning as much as it normally would. The result is that at 100 degrees C the oil has thinned only as much as the higher viscosity number indicates. Another way of looking at multi-vis oils is to think of a 20W-50 as a 20 weight oil that will not thin more than a 50 weight would when hot.

So the first number is how thin the oil is - the lower the number the thinner the oil is when cold and the lower drag on the cold engine.

The second number is how thin the oil is when hot when compared to a 'standard' oil as defined by SAE. The higher the number the thicker the oil remains when hot.

It's a question that I get asked quite frequently

Hope that helps

86C4EVER

I did not know there was such a thing as 15W-30.
Was that a typo or is that oil availlable.?
Fred

rws.1

86C4ever.... good question I checked the web site No Mobil 1 15W30 only 15W50....

86C4EVER

I guess I could have checked the Web Site myself :o
Thanks
Fred

TheStef

Sorry, you guys are probably right... 15w-50... as you can tell I don't know much about oil, but after this post I know a lot more.