What is the best oil viscosity for my area climate?

Hi, in my area early mornings in winter time may fall to 3掳 0r 4掳 C, and during summer days it may climb to 27掳 or 28掳 C, while most of the year the daily temperature ranges from 10掳 to 22掳...


I know that most manufacturers today recommend using 5W-30 all year round, but I've been told by in a good garage that 15W-40 would fit best my needs... I own a Ford Focus 1998.


I'll appreciate all the suggestions from your experience.What is the best oil viscosity for my area climate?
Use whatever your owner's manual says to use.





Oil viscosity requirements use to be determined by outdoor temperature.





That is no longer how they are figured. Let's face it, once your engine is warmed up it will run at the same internal temperature in the summer and winter.





Some Honda vehicles now call for a 5W20 oil year round and others call for a 5W30 oil. A lot depends on how the engine is designed and the tolerances of the engine.





Use what Ford recommends for the Focus. If they recommend 5W30 or 10W30 then you can also use 0W30 but not 5W20 or 0W20. If they recommend 5W20 then you may use 0W20.





DON'T listen to a good garage, they are only telling you what they know from the old school way of doing things. The car manufacturers have technicians who are much more qualified than any local garages.





Thicker is Better Myth


The reason that oil viscosities have gotten thinner is because bearing clearances have become smaller. Using thicker oils will interfere with oil flow and the oil pressure will increase. In a worn engine it may be okay to increase the viscosity of the oil because the bearing clearances have become larger. http://www.nordicgroup.us/oil.htm#Why%20鈥?/a>What is the best oil viscosity for my area climate?
Stick with the 5w-30 all season oil. 15w-40 is way to thick for that model/year and for those temp fluctuations. Where I live in the US the temps are from -40 to 100 degrees F. I say to stay with what the manufacture specifications recommend.





I do and no problems.
im a fan of 10 w 40 in summer and 5w 40 winter.....todays oils r very good...the 40 gives MORE protection and the first # is thickness... the 5w flowes better in cold
Ford in the UK recommend 5W30 for the Focus, for all year round, so I would stick with that. 15W40 will be a lot thicker when cold, so will not lubricate the engine as well. Chances are a 15w40 will not meet the recommended specification (WSS M2C913-B or -C) for the engine either.





Oil selection has become a lot more difficult in the last few years, as engines get more precisely manufactured and more complex in their design. Even within a particular grade (eg 5W30, there might be 5 or 6 different types). Look at either of the websites below and you can check what oil you car should take.
The number after the W should always be the same as recommended by the manufacturer. In this case, it is a 30, so leave it at 30. The first number should be as low as possible. For 30 weight oil that is typically 5.





That is how the manufacturer came to the 5W-30 number.





If the manufacturer specified engine bearing clearances to be small, then 5W-20 would be recommended.





The number after the W is the weight of the oil which determines the oil viscosity after the engine has warmed up. This temperature is about the same for any car in any climate unless it overheats.That is why you should keep the number the same. The engine is designed to run with 30 weight oil when warm.





The number before the W is the weight of the oil at 0 deg. F. Cold oil is thicker than warm oil. The number before the W means that the oil is modified to be thinner when cold than straight 30 weight oil. In warm weather, but much worse in cold weather, the 30 weight oil cannot lubricate the engine as well. Modified oil such as 5W-30 is used to provide thinner oil weight at low temperatures and the regular oil weight once the oil warms up.





This dual oil weight is done with polymer modifiers. The modifiers curl up into a ball when cold. As they warm up, they stretch out into a star shape. The expanded shape cause the oil to thicken up. For example, take straight 5 weight oil and add modifiers. When it's cold, it is 5 weight oil. As it warms up, it could be 20 weight or 30 weight depending on how many modifiers are added.





That is how 5W-30 is made.