I bought a quart of rotella 15-40 for my lawn mower and he started to argue with me about the thickness of the oil. I said the 15 is the viscosity of the oil in cold and the 40 is the weight at operating temp. He said he’s changed thousands of gallons of oil and oil is always thinner when hot than cold, basically saying I had the numbers of the weight backwards…
Autozone guy trying to confuse me
- Thread starter Mid570
- Start date
Whenever I come across people with this kind of attitude I just say "yep sounds about right" and continue on my way. It's not worth the effort since they will never be willing to be open minded.
That's what I do, yes them to death and move on.
Oh he’s wasn’t getting that technical about it. He basically was saying that all oils get thin when hot.
OVERKILL
$100 Site Donor 2021
He's right.
The number in front of the W is the Winter grade of the oil. This is a totally different measuring system than the number AFTER the W, which is the SAE grade for the lubricant and measured at 100C.
The 15 doesn't mean that the oil would flow like a 15 "straight weight", which should raise an eyebrow anyway, since SAE 15 doesn't exist.
The 15W means that it meets the Winter Grade CCS and MRV requirements for the 15W designation, tested at -15C and -20C respectively. These are NOT KV values (though there is a KV100 floor for the Winter grade) but rather a Cold Cranking Simulator Test (CCS) and an oil pumping test (MRV):
Yes physics still rules even with a multigrade oil.
I think he was thinking that since the oil is thinner when hot, that means it’s a 15w and thicker when cold, that’s the 40.
OVERKILL
$100 Site Donor 2021
As noted, the 15W isn't a viscosity, it's just a Winter grade that corresponds to CCS/MRV performance, so the 15W just basically tells you it's good to use down to -15C or so.
The number AFTER the W, in this case, a 40, means the lubricant's viscosity at 100C falls within the range for the 40 grade designation.
I took this from the Castrol webpage. Maybe they oversimplified?
If you need a 15W-40 diesel oil, Castrol® GTX® Diesel helps extend engine life, protecting against the wear and tear of severe weather, rough roads and heavy tows. As a 15W-40 viscosity grade, it flows like a 15 weight oil from start up in Winter, but provides the protection of a 40 weight once the engine reaches full operating temperature.
Please tell him that lol
OVERKILL
$100 Site Donor 2021
Yeah, that's horribly wrong, lol. First clue should be that a the 15 grade designation doesn't exist in J300, lol, only the 15W grade, which isn't defined by KV but rather CCS/MRV.
You can blend a 15W-40 without any VII's using PAO, so it would simultaneously be a 15W-40 and SAE40 lubricant, or worded differently, it would meet the requirements of the SAE40 grade designation as well as the 15W-40 multigrade designation.
I put Duron SAE 40 in my brand new 174cc Canadian Tire lawnmower. I’ll bet that oil would pass the 25W cold flow, pumping and cranking tests making it a 25W40. Duron SAE 30 is likely a 20W30.
thanks
OVERKILL
$100 Site Donor 2021
You are quite welcome
It's all a matter of degrees...
If folks would stop using the word “weight” when discussing engine oil it would help. I think that confuses people. Most I talk to about oil who have never really looked into it think the W stands for weight and oil is classified by weight. I thought oil came in grades. I had a guy at the brake shop tell me that the “0 weight” Mobil 1 I was running in my car was too thin and would ruin my engine. I said no it’s a 30 grade oil. That’s what the car is spec’d for. I didn’t argue with him though. Didn’t have the energy.
Yep.…
About 15 years ago, I had a mechanic at the Navy Exchange try and stop me from buying 0W30 Castrol (much loved on BITOG) on clearance.
“That zero weight won’t give you enough oil pressure on start up. It’s too thin. You need a 10W30.”
He was honestly trying to be helpful. And we talked for a bit, but he stuck to that point of: it is too thin on start up. I thanked him, moved to another row in the oil aisle.
And when he went back out to the service bay, grabbed two cases of that Castrol 0W30 that was on clearance.
