Originally Posted By: Zako2
Originally Posted By: JackB1
Since this thread involves 5/20 vs 5/30w, AGAIN, I am still confused of whether to use the reccomended 5/20 in my Jeep 3.7 or 5/30 which several studies have shown to give better engine life. Supposedly, and the opinions vary, the 5/20w suggested by many manufacturers was to help with fuel mileage for the CAFE standards. They run it in the test to get the higher mileage [a little may mean a lot to manufacturers] and consequently are required to reccomend it to the purchaser. Could anyone clear this up. 5/20 is a little more difficult to find when shopping oil in some places like warehouse clubs.
I never buy such arguments from internet "experts", unless it's indeed a well studied case where the car manufacturer appears to be wrong. You can't imagine how little people know about motor oil on average. You may have a point here, but I have heard so many times people argue for many other vehicles, including those relatively easy on oil, to choose 5W30 over 5W20, even though 5W20 is the recommendation of car company. One argument I heard is that this is because "5W30 pours better". Another (misguided) argument that I frequently hear on forums is that 10W30 is a good summer oil for a 5W30 engine. (why??? beats me) There are a lot of people on the internet who seem hostile to 5W20 oils because they think that 5W30 was the one and true oil, and 5W20 was recommended ONLY for fuel economy reasons. Well, you may want to read the "Motor Oil University" articles on this web site to see that many of those are wrong. Once engine is running at it's normal temperature, the oil temperature is around 100C. At this temperature, 5W20 is only slightly thinner than 5W30. However, when the engine is cold or not warm enough, 5W20 flows much better than 5W30, and 5W30 flows better than 10W30, usually, reaching parts of engine much faster. This is important because a lot of wear happens during the first few minutes of use, specially if you drive hard. So, there 5W20 certainly has its advantages, SPECIALLY in colder climates. When the car manufacturer recommends an oil grade for their engine, 99% of the time, they're right. THEY NOT stupid. They know their engines.
And then, you live in a colder climate. Hands down, go with the thinner oil. Choose 5W20 over 5W30, and during months with freezing temperature starts, choose a 0W grade oil over 5W.
Just to play devil’s advocate.
I was with you all the way until the last sentence. You do realize that most manufacturers do not recommend 0w oils right? Then how can you keep saying that manufacturers know their engines best, on one side of the argument, and then recommend an oil weight that is NOT recommended by a lot of manufacturers, on the other side of your argument?
You either stick blindly to what manufacturers recommend, or you accept that people will use whatever they think is right or suits their needs. In most cases either choice will not doom the engine or shorten its service life.