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William Schnieber · 07-11-2016, 10:40 AM

I know this has been hashed out before and I've searched and read a lot of comments. However, I'm going to change the oil myself. I have. A 2005 Alpine Limited with the ISL 400.
What is the difference between 15-40w and 15-30w? Delo 15-30w is almost 50% off right now on Amazon. I only have 32k miles on the coach and about 10k on current oil. Did a oil analysis a couple years ago and it was marginal so now it's time. Thanks for your inputs.

William Schnieber · 07-11-2016, 10:42 AM

Here is what I'm leaning toward.

Mr_D · 07-11-2016, 10:50 AM

The difference is: What does Cummins call for in your area of usage/temperature range?
I've used nothing but 15w40 in my Cummins her in the Pacific NorthWet.

William Schnieber · 07-11-2016, 10:55 AM

Cummins calls for the 15/40 Valvaline. I'm in Southern Calidornia. Is the 30 a thinner weight? Is 10w going to make that much of a difference? Probably should stick with what Cummins recommends.

wolfe10 · 07-11-2016, 11:00 AM

Quote:

Originally Posted by William Schnieber

Cummins calls for the 15/40 Valvaline. I'm in Southern Calidornia. Is the 30 a thinner weight? Is 10w going to make that much of a difference? Probably should stick with what Cummins recommends.

No question 10/30 is thinner than 15/40. And certainly in southern CA, I would use the 15/40! Never used or even heard of 15/30-- not offered in our area (Texas).

Brett
2003 Alpine 38FDDS

William Schnieber · 07-11-2016, 11:16 AM

This is a no brainer, I'll use what Cummins recommends...problem solved.

Old Scout · 07-11-2016, 04:05 PM

Agree--go with 15w40 and don't look back. Curious though--you said you did an oil analysis "a couple year ago and it was marginal...so now it is time to change oil..." Normal ops procedure from Cummins is to change annually, regardless of mileage.