0W40 instead of 10W30?

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My engine (4.0L Jeep) calls for 10W30 and I've been using Mobil1. Would it work to use 0W40, or would this oil to be too viscous at temperature compared to XW30? One thing I've thought about is that Mobil1 tends to be on the thin side, so maybe 0W40 is on the thin side of 40wt and would be close to a thick 30wt. Jon
 

Patman

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Mobil's 0w40 is actually right in the middle of a 40wt, it's not on the thin side like their other viscosities. To be a 40wt it must be between 12.5 to 16.3cst at 100c. Mobil's 0w40 is 14.4. I think it's probably safe to run though. As I mentioned in another thread, when a car maker recommends an Xw30 oil, it's safe to go one step higher to an Xw40 oil, if you're gonna drive it hard and/or drive it in very hot weather. I normally would shy away from oils with such a large spread like 0w40, but this new Mobil 1 0w40 sounds like it is very shear stable. I'd still probably go with a 15w40 myself if I was going to go thicker than my good ole 10w30.
 
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quote:
Originally posted by JonC: My engine (4.0L Jeep) calls for 10W30 and I've been using Mobil1. Would it work to use 0W40, or would this oil to be too viscous at temperature compared to XW30? One thing I've thought about is that Mobil1 tends to be on the thin side, so maybe 0W40 is on the thin side of 40wt and would be close to a thick 30wt. Jon
I don't see any reason to use the 0W40 if your manual calls for 10W30 and you haven't had any problems with it. The only reason I use 0W40 is that my manual calls for a 5W40 ACEA A3 rated oil, and I have actually used 5W30 and gotten very good analysis numbers.
 

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I am a proponent of heavier oils-even though it may not be really necessary. You could get a little heavier "brew" by mixing in a quart of M1 15W50 (thats what I currently do)
 

JonC

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The only reason I'm considering the 0W40 instead of 10W30 is because of the positive reviews I've heard on the 0W40. I think I've heard it has a higher level of anti-wear additives than the rest of the M1 line. Jon
 
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quote:
Originally posted by Patman: Mobil's 0w40 is actually right in the middle of a 40wt, it's not on the thin side like their other viscosities. To be a 40wt it must be between 12.5 to 16.3cst at 100c. Mobil's 0w40 is 14.4. I think it's probably safe to run though. As I mentioned in another thread, when a car maker recommends an Xw30 oil, it's safe to go one step higher to an Xw40 oil, if you're gonna drive it hard and/or drive it in very hot weather. I normally would shy away from oils with such a large spread like 0w40, but this new Mobil 1 0w40 sounds like it is very shear stable. I'd still probably go with a 15w40 myself if I was going to go thicker than my good ole 10w30.
Patman, Is this Mobil's new synthetic "European" formula you are referencing, as I've only seen 5W/40 in my local store..... Has anyone actually performed a baseline analysis of this viscosity?
 
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I have not done a 10W30 baseline, but I have sent the 5W30 in. Should have the results sometime this week. I'll pull a sample of the 0W40 when the change oil light come on again, probably be 6-8 weeks. This will be 5W30 tri vs 0W40 SS, but I really doubt there is much difference in the tri vs SS. We had a pretty long discussion on this ealier. http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=000087
 

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Bill, yes this is Mobil 1's European Formula (which is sold in the US also). Based on some recent threads in here, where a few top chemists have said how good it is (even though they work for other companies!) it sounds like this version of Mobil 1 is a good one. It's a good alternative for those that don't like how Mobil 1 10w30 is more on the low end of the 30wt scale. [ August 18, 2002, 08:26 PM: Message edited by: Patman ]
 
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quote:
Originally posted by VaderSS: I have not done a 10W30 baseline, but I have sent the 5W30 in. Should have the results sometime this week. I'll pull a sample of the 0W40 when the change oil light come on again, probably be 6-8 weeks. This will be 5W30 tri vs 0W40 SS, but I really doubt there is much difference in the tri vs SS. We had a pretty long discussion on this ealier. http://theoildrop.server101.com/cgi/ultimatebb.cgi?ubb=get_topic;f=1;t=000087
V aderSS, In my oil analysis spreadsheet, I've already done baselines on the following Mobil oils: 5W/30 Tri-Synthetic 5W/30 SuperSyn 10W/30 Drive Clean Blend If you want to take a gander, e-mail me for a link: If you don't mind sharing, I would be interested to see if your analysis comes up with any differences or if it remains in line. Thanks for that other post link, the statements made me curious originally because I've only seen 5W/40 at my local AutoZone and not 0W/40...... [ September 11, 2002, 09:29 AM: Message edited by: bill99gxe ]
 
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quote:
Originally posted by bill99gxe: [QBThanks for that other post link, the statements made me curious originally because I've only seen 5W/40 at my local AutoZone and not 0W/40......[/QB]
Are you talking about Mobil1 5w40? I could not find it on their website nor at the AutoZones in Dallas. They do have the 0w40, though.
 
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quote:
Originally posted by Chris A:
quote:
Originally posted by bill99gxe: [QBThanks for that other post link, the statements made me curious originally because I've only seen 5W/40 at my local AutoZone and not 0W/40......

Are you talking about Mobil1 5w40? I could not find it on their website nor at the AutoZones in Dallas. They do have the 0w40, though.[/QB]
Yeah, I guess I should go look again, as I seem to be the only one who has seen 5W/40.....perhaps I didn't see it right. [Embarrassed]
 
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I'll post on this forum with the results. I don't have any trending, but if 0W40 is as good as I think it is, there should be a noticeable difference. I ran the 5W30 until the change oil light came on. Usually I change it at 7500, but in the interest of getting a quicker comparison(and a more accurate one) I've decided to use the change oil light as the reference. This should ensure that each sample is equally stressed.
 
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JonC, My father in law has been running the amsoil 10w-40 year round in his Jeeps for the past 12 years - I can't convince him to switch to the low viscosity stuff. The mobil 1, 0w-40 will work just fine, although the main reason I see for using it is that the additive chemstry may be a bit better than the 5w-30/10w-30 versions. I say this because it meets the ACEA A3/B4 engine tests for gas and diesel passenger car engines. The diesel tests require higher detergency so the 0w-40 should hold up better (TBN retention) over a longer change interval. Shear stability will probably be better with the 10w-30 if I had to make an educated guess .... Ted
 
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I will probably not run a Xw40 in my 2002 Yukon (no, Terry, it doesn't have piston slap) because of the high oil pressure. At idle, it has 50psi of pressure and I'm sure it is compressing the pressure bypass spring under any throttle. Since this oil is going through the pump, it is heating up, just to be dumped back into the pan.
 
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Is that pressure measured with the stock gauge, or has it been measured with an aftermarket or a mechanics gauge? The reason I ask is that many times the stock gauge is very inaccurate. Also, is you gauge actually measuring pressure or is it in reality, an "idiot gauge?" Many vehicles gauges don't actually measure pressure at all, but hook up to a pressure switch and give the same reading at all times. If it always goes to 50, and never changes with RPM and temperature, then it is proably an "idiot gauge."
 
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Yes, it is the stock gauge. It's definately not an idiot gauge. It moves depending on cold, hot, idle, under throttle. I think I'm going to put the 0w40 in the wife's LS1 Firebird on it's next change and see what it does to the oil pressure, which normally reads 40 psi hot idle. It's got over 60k miles and may be a little looser than the new Yukon, but we hardly put any miles on the Firebird these days.
 
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Chris A Normally the pressure gage is located after the filter. The gage only measures the pressure in one spot. It doesn't measure pressure differential before the filter and after it. I doubt your filter is in by-pass as often as you think it is.
 
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Deep down, I suspect that anyone running any good synthetic, xW-30, xW-40, xW-50 will never see enough wear internally (in a sound engine) to ever have a problem. Yes, there might be a slight difference in wear metals ppm, and there might be a slight difference in mpg-- but the body will most likely fall apart first! (unless a mechanical problem in the engine occurs).
 
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satterfi, I'm talking about the pressure bypass spring in the oil pump which keeps the pressure from going through the roof.
 
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I'd have a mechanic measure it to see if that is the correct pressure. Like I said, they are notorious for being way off.
 
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