could 15w40 cause overheating in a V10?

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Jul 10, 2003
Hermiston, OR
I've been running Delv. 1300 in my Ram V10 for about a thousand miles. I've noticed that it has ran about 10-15 degrees warmer. The outside temp has been in the 80s for the last while, so it hasn't been extremely hot. My truck has ALWAYS ran around 200degs. or less. Noticed it staying around 210 or so, never overheating. There's nothing wrong with my cooling sys. Well, What I did was changed over to M1 SUV, and now it's seems to be back to normal. I've ran it hard and never got over 200. Been in the 90s here. Could the heavier oil cause it to run hotter(though it's not technically overheating?)
Yes, It is not uncommon for temps to rise a bit with a thicker oil. Thicker oils do not transfer heat as well.
They are both 40 weight oils. That means that at least approximately within a given range the6y have similiar viscosities when running ( the M is thinner on startup ). So its a bit of a riddle as they are botehr nearly equally thick. The M1 SUV may be a bit more friction modified and perhaps we should look here. Fred... [Smile]
The viscosity info from the product data sheets seems to indicate that Delvac 1300 15W-40 would perform as a thicker oil than M1 T/SUV. Delvac 1300 15W-40 is 15.6 @ 100C with 4.3 HT/HS. M1 T/SUV is 14.8 @ 100C & I'm guessing HT/HS is below 3.5 since it isn't listed. And as Fred indicated, since Delvac 1300 is spec'd for off road equipment use, a component of the additive package could also contribute to the rise in temperature.
It will not cause any over heating at all. 10-15 degrees is nothing major. If a car has a needle for temp guage 10-15 degrees would not even be perceptable on the guage by most people. Seeing how both oils are a 40Wt. I do not think viscosity matters much in this situation. It is more likely that the PAO and Ester base stocks are simply tranfering heat more effeciently and reduceing friction so less heat is being generated! [ June 06, 2004, 11:42 AM: Message edited by: JohnBrowning ]
Gents I've run 5w-30 and 10w-60 (both synthetic and both approved by the vehicle manufacturer for the engine) and my observation was that the thicker oil ran hotter. The engine ran about 10 Degrees C hotter (about 18 degrees F) under the same conditions. The HTHS for the 10w-60 was about 5.7 and the HTHS for the 5w-30 was 3.6. It's interesting that the higher temperature results in a much smaller "running viscosity" difference between the two oils. Cheers JJ
in the blurb about diesel engine oils, he doesn't state the fact correctly about using S-rated (gasoline-spark) engine oils in a diesel, which makes me wonder how much of the article is really accurate. He's right about how the oil wouldn't be able to maintain the cleanliness of the motor, and would've been better said by stating the ability of the oil to suspend soot. But the real reason why you cannot or should not use an S-rated oil is because the oil is used to operate the hydraulic fuel injection pump and the oil gets pressurized to a few thousand or so psi. A S-rated oil will foam under those conditions and the engine will not get proper fueling, have loss of power, sputter, etc. under conditions it shouldn't. A C-rated oil will not foam.
Howdy, Thanks everyone. I was noticing my water temp hotter than the norm. I have since switched back to M1 SUV and it hasn't gotten hotte since. This is just everyday around town and highway driving, no towing. [Patriot] [ June 08, 2004, 10:57 PM: Message edited by: Doug ]
Doug, The key is that PAO/Ester based synthetics reduce friction and dissipate heat more effectively than petroleum oils. So even if you substituted a 10w-30 petroleum oil with a 10w-30 synthetic like Amsoil, Mobil 1, Redline, etc, you would expect to see a reduction in peak oil temps. A significantly thicker oil using the same basestock does make the engine run hotter....I've used the Amsoil 0w-30 and 20w-50 in my Audi - both the Series 2000 formulations - and the peak oil tems are about 10F-15F cooler with the 0w-30. The difference in oil pressure between these two grades is not as great as you'd expect, due to the reduced oil temps with the low viscosity synthetic. One of the key benefits of synlubes is that you can run these low vis, 0w-30/5w-30 fluids; get the drop in oil temps and still get excellent protection. Minimizing oil temps helps control excessive thermal expansion and the power loss that occurs. It also helps extend the life of elastomeric seals and gaskets.... My recommendation is to use the THINNEST oil that will give you acceptable oil pressure under high heat/high load conditions, ie pulling a trailer, driving up mountain grades, etc. Something on the order of 10-15 psi/1000 rpms, for a low rpm domestic engine and 15-20 psi/1000 rpms, for high rpm, imported engines like VW, Audi, SAAB, etc that typically run higher oil pressures. Oil pressure higher than the upper end of these ranges means that the oil is too thick and the engine is running too hot .... Tooslick [ June 08, 2004, 12:18 PM: Message edited by: TooSlick ]
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