Blackstone newsletter - Can You Use a Thinner Viscosity Oil?

[Ecky]

Well, do you want a thinner viscosity when cold, or when hot? A 5w40 and 15w40 should both have a similar viscosity when warm, just as a 5w20 and 5w40 should have a similar viscosity when cold.

[Hersbird]

Best mpg potential when hot but without doing any harm. Also less expensive to purchase up front is better as well but not as important. I'm not looking for the cheapest but I'm also not going to spend Amsoil money either.

[Tulok]

Originally Posted by Hersbird

Best mpg potential when hot but without doing any harm. Also less expensive to purchase up front is better as well but not as important. I'm not looking for the cheapest but I'm also not going to spend Amsoil money either.

Run exactly what cummins recommends. Cummins engines, if you just go exactly by the book will go 500k+ without a problem. Going 500k or more miles will save you so much more money than experimenting with different oils just to see. You bought the right truck, just go by the book and change the oil right on time and the engine will last longer than the body sitting around it.

I've seen people pull a 300k mile Cummins out of a truck and put it in another truck and put another 100k on it and get 18mpg highway or more without any major trouble.

If you've got a 12V and your MPG sucks, you already know the answer to better MPG, and if you don't then just google "How to get better MPG 12v cummins" and read read read

[Baltothewolf]

Yea those Cummins will push 750,000-1,000,000 miles if you just take care of them mechanically and don't beat them up.

[ProDigit]

Thinner oil mostly has more synthetic oil mixed in.
It works well with modern small engines. Eco cars.
Like a Chevy spark (1.25-1.4 liter), Chevy sonic/cruze (1.4 liter turbo/1.8l NA), Nissan Versa (1.6-1.8liter), Ford Fiesta (1.5-1.6 liter), Dodge Dart (1.4l twin turbo), etc...

The engines are not generating high heat, and are cooled additionally well by the watercooling. Back in the days engines like these ran aircooled (up to 1.8 liter); and thicker (higher heat resistant) oil was required.
But not anymore.

[ksa8907]

Originally Posted by MobilOne

My experience with 10w40 Mobil One synthetic is that I get many miles of use out of my engines. 200k miles on my 2001 Silverado, 320k miles on my wife's 1999 Avalon (so far). I change the oil and filters at 4000 miles. I've tried 5w-20 in the truck and the lifters rattled a lot; so I changed that out after 1000 miles. Now, I live near Atlanta, so it doesn't get as cold here as some places. If I still lived in Michigan, you can bet that I would use a thinner oil. And if I had new cars I would use a thinner oil.

Years ago, I used to see advertised an electric auxiliary oil pump that was used to circulate the oil prior to starting the engine. If I lived in a cold climate, I would look for one of those.

My old car, 2000 dodge intrepid with the 3.2 engine, recommended 10w30 but the lifters would rattle. I always used 10w40 year round and that engine ran like a champ, sold it at 225k miles.

[NHB]

Thinner oils are also easier to keep clean. Filters work better with thinner oils. When oil stays cleaner, there will be less wear to the components.