Engine/Transmission (1994 - 1998) Switch from 15w-40 to 5w-40?

[GROBBINS]

My current oil supplier switched brands and I found a replacement, but realized the oil viscosity was 5w instead of the 15w that I had been using for years. Truck does not get used everyday and has 250k on it.
Should I use it or return it?

 

[SnoKing]

I would return it. Most diesels call for 15w-40.
SNOKING

 

[JR]

Is it a synthetic? I believe all 5w40 is but not 100% sure. The only difference between the 2 is that the 5w40 will be slightly thinner at startup (not necessarily a bad thing)

Once up to operating temperature they are both the same viscosity.

 

[JMcCoy]

I wouldn't worry about it.

 

[SnoKing]

Is it a synthetic? I believe all 5w40 is but not 100% sure. The only difference between the 2 is that the 5w40 will be slightly thinner at startup (not necessarily a bad thing)

Once up to operating temperature they are both the same viscosity.

JR is probably right! It is synthetic! The question is do you want to run synthetic in an older truck with a lot of miles?

SNOKING

 

[JR]

JR is probably right! It is synthetic! The question is do you want to run synthetic in an older truck with a lot of miles?

SNOKING

Why wouldn't you?

 

[SnoKing]

Why wouldn't you?

I would have a concern about it starting to use oil. But someone with more knowledge that I should be along to give guidance.

SNOKING

 

[JR]

I bought my 98 in 2010 and switched to synthetic and have had no issues. The benefits far outway the drawbacks IMO.

 

[Cummins12V98]

My red 98 has about 400K on it and has used AMZ/OIL 15-40 Diesel Marine oil since about 55K.

 

[E7mack96]

We are switching trucks with 500K+ miles over to Delvac 5w30 synthetic and running 50,000 mile intervals. Your truck should be fine.

 

[Mikey-KE7LBB]

http://www.bobistheoilguy.com/motor-oil-101/

Start off with this one and read all of the links until your head hurts!! 0W-40 would even be fine

 

[GROBBINS]

It is synthetic. It's also the same manufacturer that I've been using since I bought the truck, actually the original owner recommended it to me. I've always had trouble finding it though, I used to drive 45min to a truck stop to buy out their 3 gallons off the shelf. Its hard for me to keep track of the oils with all the new marketing labeling over the years. So when I saw synthetic oil for diesel truck at a local store, I thought better buy these while they're here. And didn't realize until I was home that I used the 15w. I did as much research as I could take over the internet, and it seems that I would be ok. Thanks for all the input, its greatly appreciated.

 

[AnOldBiker]

Last winter, it was -7* here, which is not to often, thank God. But seeing you live in Wisconsin, you would be better using 0w-40 year round. From what I read in the past, when you start your engine and the oil is ambient in temperature, the flow rate of the oil is the same as 5w, and your bearings are protected. When your engine obtains higher temperatures, it flows like 40w. But all the time it is rated as a 40w oil. The flow rate protects your engine. Since I use 5w-40 year round, I never worry when I start my engine no matter where in the country I'm at. But if I lived where you live, after seeing the temps of last winter, it would be 0w-40 only.

I had a truck with over 200k on the clock and changed to full sync oil and never had an issue. I sold it with 400k and the next owner was using doing the same. If you have a leak, it will leak. If you don't, it won't start one unless the gasket is weak. This will happen if you use dino or sync oil.

 

[GAmes]

I switch back and forth, 15w40 in the summer, synthetic in the winter. Unless you have an oil bypass filter system the oil needs to be changed just as often, so using dyno oil in the summer saves me money. There have been times that I have changed oil a week after the last change though, so your situation might vary.