Sounds good Tooslick. From what I have gathered from looking at todays data sheet numbers compared to 7-10 years ago, pretty much all name brand conventional 10w30 oils will easily pass the 5w MRV pumping limits (in fact, many conventional 10w30 oils would do better than 5w-40 Rotella Synthetic in the MRV test). However, they won't pass the CCS limit. Certain synthetic 10w30s will pass both I think. Amsoil seems to be the only 1 I know of that comes close to being 7,000 Cp at -30 C. Mobil 1 won't do it; Redline/Royal Purple don't even come close. Royal Purple especially, has terrible cold weather specs. Amsoil ATM simply blows Royal Purple 10w30 away per data sheet info. (all this assuming that MRV/CCS numbers double with every 5C you drop; I read here that's a safe assumption ?).
Thick Oils, Cold Weather, Engine Wear???
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I think the doubling was with dino and for synthetic it was somewhere around a factor of 1.7.
I thought the "W" number is an indication of the "starting" and "pumping" characteristics. Back when engines had carburetors, how fast the starter could crank the engine determined if it would start at all. Therefore, a lower "W" value meant the oil was thinner, and the starter motor could crank faster for easier starting in cold weather. With fuel injected engines another low temperature phenomena became important. If the oil was cooled slowly (as in over a weekend,) it could set up and harden in the sump. The engine could still start and run, but the oil would not be sucked through the oil pump pickup tube. The pumping temperature is just the lowest useable temperature for the grade of oil for fuel injected engines.
Information from old Mobil site on the MGB Suggested the following guide
5W20 below -6F
10W40 Above -4F
15W40 Above 14F
20W40 Above 32F
Information from old Mobil site on the MGB Suggested the following guide
5W20 below -6F
10W40 Above -4F
15W40 Above 14F
20W40 Above 32F
Pablo, I think TooSlick is stateing what guidelines are used not what best practice is! Even I have more conserative cutoffs then what is recomended. I would never run a conventional 15w40 or thicker below 15°F even when really smart engineers say it is ok! I actualy switch my thicker oils out once the nightly lows start to hit high 20's to low 30's area as I know it is only a matter of time before winter hits. I seldom use super thick conventional oils any more so it really is not an issue. I think synthetic oils are another ball of wax. I also try to use more 5W40's now then ever before. I have proofed Redline 5W40 in -18°F weather! Now that 5W40 synthetics are here I think a lot of us will likely be able to
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Correct, but in the case of fully synthetic and HC oil, as long as they meet the approved spec (which does include viscosity), the ambient temperature chart is usually open towards the colder and higher temperature without any limits shown.
[ April 11, 2005, 10:18 PM: Message edited by: moribundman ]
My faith in at least one Amsoil dealer has been restored.quote:
Originally posted by Pablo:
TS I realize that. I've been saying that for the last 2-3 years. It's why have have the confidence to run AME year around.
Honestly though a conventional 15w40 at -4° still is way too viscous for my tastes....even 10°F is pushing it IMHO. It may pump and flow, but.....well...stick with the owner's manual!!
Did you ever consider AutoRXing this engine?
Clearences get bigger when cold I think. That's why they list a smaller valve lash setting if the engine is warm, and a bigger lash for a cold motor.
Depends what you're measuring, and what they are made of. For example, a steel crankshaft in an aluminum block.
http://niuhep.physics.niu.edu/~willis/phys250/chapter_12_day_1.html
[ April 16, 2005, 08:47 PM: Message edited by: 427Z06 ]
Lay off the "sauce" Pscholtequote:
Originally posted by pscholte:
Ted,
Is it OK if we engage in "head whipping" and "pencil scratching?"No? OK, Just thought I'd ask.
If synthtic oil takes longer to heat up it may be better to use a thinner W Synthetic compared to a Dino. Reaching engine operating temperature as quickly as possible should help in areas of engine using dissimilar metals, and preheating engine/ keeping engine as warm as possible overnight.
Again if Synthetic runs cooler at operating temperatures a thinner Synthetic perhaps should be used compared to Dino.
Again if Synthetic runs cooler at operating temperatures a thinner Synthetic perhaps should be used compared to Dino.
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