Syn Oil Viscosity Question

[McLeod]

...new owner of a 2003 2500HD with 6.0 -- 125,000 miles. The previous owner has used Mobil 1 since new and says it's important to use 10-30 instead of 5-30....says that there's a particular problem unique to the Mobil 1 that makes it so. I've made the first oil change and used the 10-30 and, of course, it seems to work/run fine, but I have to wonder if it may makes sense to use what GM recommends, 5-30? Thoughts/experience? Thanks! Mc

[txab]

I know of no particular problem with Mobil 1 5w-30. But you are fine running the 10w-30. GM says "SAE 10w-30 is acceptable if 5w-30 is not available". Their chart shows use down to zero degrees F. I'm currently running 10w-30.

[mxdirtrider56]

10W-30 will be fine. Especially in a truck with 125,000 miles. It is not uncommon to run that weight in trucks with higher miles.

[Z45]

A 0W-30, 5W-30 and a 10W-30 will be same viscosity at normal operating temperature, they have to be to meet SAE spec's for a 30 wt oil. The only difference is their cold start properties.

 

 

Oil weight, or viscosity, refers to how thick or thin the oil is. The temperature requirements set for oil by the Society of Automotive Engineers (SAE) is 0 degrees F (low) and 210 degrees F (high).

 

Oils meeting the SAE's low temperature requirements have a "W" after the viscosity rating (example: 10W), and oils that meet the high ratings have no letter (example SAE 30). An oil is rated for viscosity by heating it to a specified temperature, and then allowing it to flow out of a specifically sized hole. Its viscosity rating is determined by the length of time it takes to flow out of the hole. If it flows quickly, it gets a low rating. If it flows slowly, it gets a high rating.

 

Engines need oil that is thin enough for cold starts, and thick enough when the engine is hot. Since oil gets thinner when heated, and thicker when cooled, most of us use what are called multi-grade, or multi-viscosity oils. These oils meet SAE specifications for the low temperature requirements of a light oil and the high temperature requirements of a heavy oil.

 

You will hear them referred to as multi-viscosity, all-season and all-weather oils. An example is a 10W-30 which is commonly found in stores. When choosing oil, always follow the manufacturer's recommendation.

[the hammer]

I agree, 0w-30. 5w-30, and 10w-30 have same thickness rating at operating temps, hence all of them are 30 weigh oils.

 

I use 0W-30 German Castrol Syntec in mine, and have use Mobil one 5w-30 in my other cars. You are fine with 10w-30. It is all a 30 weight when it warms up. Some are thinner and some are thicker 30 weights, but it is still rated as a 30 weight. Gets too technical and my head may explode.

[McLeod]

So that's why my head hurts! You guys have given me exactly what I needed...and, my headache is going away. I'm gonna be happy with the 10-30 and expect many more (relatively) trouble free miles from this ole truck. Mc

[RaddHazzard]

He possibly said 10w and not 5w because at some point in the recent past the 5w30 was found not to meet certain specs it claimed, didnt prevent wear good enough in a certain test. This has since been corrected by Mobil. All this is from memory from reading on the oil geek website so i could be off.

[dlstewart01]

0w, 5w, 10w, etc.is not weight but an somewhat arbitrary rating based on the oil low temperature flow and pumping characteristics - SAE J300 (1999) Motor Oil Grades- Low Temperature Specifications. I say somewhat arbitrary in that an oil that meets the 0w standard can be rated 5w or 10w because of the myth that "W" means weight ( it means winter) and 95-99% of the folks that recommend/sale/change oil believe this myth. We have all heard "I would not use a 0 weight oil in your car.".

[[email protected]]

I've always used 10w-30 in mine. My dad always used 15w-40 in his vehicles, really can't tell a difference.

[McLeod]

He possibly said 10w and not 5w because at some point in the recent past the 5w30 was found not to meet certain specs it claimed, didnt prevent wear good enough in a certain test. This has since been corrected by Mobil. All this is from memory from reading on the oil geek website so i could be off.

That's likely exactly what he was talking about, now that I think about it. On a related note, I recall hearing an aircraft engine builder once ask the question "what's the worst thing you can do for your engine?" -- the answer was "start it". There's probably similarities with our truck engines, I would think. There must be a very close "balance" between the "10" and "05" (or "0") with the "new" syn oils when it comes to "cold, start up thickness". ...kinda fun to read and research as well as to hear from some folks here who clearly have good experience and expertise. All much appreciated! Mc

[jro909]

i use 5w-30 mobil one and no problems....your fine with 10w-30, alot of people run it if they live in a hot climate year round...heavier weight just sucks in cold cold climates, last year when it was -30 here my truck sat at 60 psi at idle for oil pressure from the oil being like paste, it also took 30 minutes for the temp needle to begin moving....but synthetic oil dosen't get pastey as much in the cold like dino oil

[Z45]

He possibly said 10w and not 5w because at some point in the recent past the 5w30 was found not to meet certain specs it claimed, didnt prevent wear good enough in a certain test. This has since been corrected by Mobil. All this is from memory from reading on the oil geek website so i could be off.

Some people get ideas in their head and nothin will change it. He might have been told that or read that on the internet or he just believed 5W-30 has to be bad because he used 10W-30 for years. I have often run into people with the same opinion and when I try to explain viscosity to them they don't understand it technically, which is often the case IMO with people who have his opinion.

 

Common sense is not all that common.