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Discussion Starter · #1 · (Edited)
Ok, most of you who have been here a while know who i am. After doing tons of research on types of motor oil; multi-grade vs. single i have come up with no definate answer to which is better than the other. In MY OPINION after researching for months, in my region (the inland northwest) BOTH grades of oil are essential for me. Temperatures range between 105 F in the summer and -15 F during the winter. These temperatures are max highs and lows. Usually during the fall (sept-nov) the average high is 60 and lows maybe 40. Winter (dec-feb) avg high 38, avg low 25. Spring (mar-may) avg high 65, avg low 45. Summer, avg high 80, avg low 60. These are estimates. So based on what i've read over the internet, single grade oils are better than multi-grade when temperatures are 32F or above. Multi-grade oils are better than single grade oils when temperatures are 31F and below. (Remeber, im in the inland northwest). With this OPINION based on my research around the internet, it would be up to the owner of their car to decide when to switch oil grades (as in; you dont have to change the oil when its 32F but you could change around 40F).

I have came up with one more question about multi-grade oil that i could not find a definate answer too. This is what sparked me to type this topic. I came up with this question:
(assume its fall, spring and summer temps)
Q; During these seasons (inland NW), multi grade oils give you better gas mileage and excellent COLD start-up engine protection during the winter. Given that its summer, fall, or spring; What does multi-grade oil have to offer for protection AFTER running engine temperatures are reached? So, its 80F outside and im using multigrade oil and my motor is nice and warmed up (no need for startup protection now) what protects my engine after startup?

So my question simplified is: How does multi-grade oil protect my engine after its all warmed up? Does the oil really thicken up so it protects my engine against those hot temps?

So, before im flamed with rejecting comments, i advise you to keep in mind its an opinion. If you disagree, then state your side and do it with respect. All opinions are welcome as this is a "disscusion forum".

Thanks for any help and advise.

Website i looked at today that urged me to post:
http://www.machinerylubrication.com/article_detail.asp?articleid=204

Quotes from above site:
"SAE 30 is preferred because of its superior protection of engine bearings at operating temperatures."
"if you can use monograde in your environment, or at least in the summer, do so."
"Considering the farther north you live, I know you have the need for multigrade oils."
 

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From my experience it seems the higher number on the oil is your "running" number. I personally will not use anything other than what is recommended by the manufacturer. Why, because they have done more research than I have and they have decades of experience over me. Anyone can throw numbers and words around to make things look the way that want but, IMO, what my oil cap says is what I use.
 

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You are right in the sense that after the engine is warmed up there is no need to have cold weather and cold start protection. So a single weight oil matched to the engine's internal temperature and outside ambient temperature is best. However that is not practical because you cannot have a warm engine start every single time. Cold engine start without adequate oil protection is when most of the engine wear occur. Multi-grade oil is a compromise but that will give you the best all round protection.
 

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I'm with Mike on this one. If nothing else you should use whatever the manufacturer states because if they find out you're using something else than what's recommended they could legally void your warrenty and you'd be SOL.

Also, I've used whatever is recommended and never had an engine related problem, so I guess it must be working.
 
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