Quote:
Originally Posted by vstech
Um, how are you determining that it is thinner? are you heating the oil and measuring it's pour speed? surely you are not touching hot oil... also is the hot 15W40 clean or dirty?
5W40 cold should be plenty thick at room temp, certainly thicker than hot 15W40...
I see no problem using it in warm weather.
John
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the concern isn't it being thick enough at high temps, it it was 5w40 dino I would DARE run that any warmer temp than about 0c ambient because the thermal viscosity breakdown would mean that it'd be wearing my engine out with a lack of lubricity at those ambient temps. I'll trust synthetic light oil at any temp simply because it's formulated to be.
that said, what should my oil change intervals be now? sooner or later? Synth isn't outrageously expnsive, but it's more than I car to spent too often.
I noticed the viscosity difference when I was pouring the still hot USED 15W40 dino into my waste tank. it didn't flow much faster than clean 15W40
BUT
my case of Syntec5W40 had been sitting in my car all day and was about -22ambient and it was pouring thinner than HOT 15W40. Also, after driving it my cold idle oil pressure goes up to 3 bar when I start then it drops ALOT quicker (because it's thinner) to normal idle pressures, of what I was expecting 1.5bar but was elated to see almost 2bar. worst case scenario would have been that my engine was too loose to run light synthetic oil witout a DROP in hot idle oil pressure.
(waste tank: I take my used oil to work and put it in the waste oil furnace
)