gthbryce

I just bought a 2001 xj with 75k on it. Engine oil is black, and I'm changing it tomorrow. I have been looking at tons of forums saying use 5w40 oil because of the flat tappet cams and others say use 10w30 because of its higher flow characteristics and this and that... All I want to know is with my low mileage engine, what Weight of synthetic weight oil should I be running that will have least wear attributes, don't shout brands. I live in Northern California where winters are short and not that cold at all and summers are hot and dry.

And Hi to everyone as this is my first post.

Dechion

Everyone has their own opinions about oil, so I will just tell you what I use and leave it at that.

I have been running 10W40 in every vehicle I have owned for the last 25 years or more, and never had an oil related failure because of the weight I chose.

That does not mean it's the best oil for you, it's just what I happen to use.

SamSissine2

I think this subject is definitely a personal choice but with some good literature and others experience the decision can be a little easier to make and understand.

I would recommend 3 articles. While they are a little lengthy the info is, atleast I think, very interesting. Oil can be beaten to death but it is honestly the most important thing when it comes to protecting the internals of the engine.

#1: http://www.bobistheoilguy.com/cms/in...=article&id=84
#2: http://www.widman.biz/Corvair/English/Links/Oil.html
#3: http://www.engineoilinfo.com/index.htm

From my perspective you are doing the engine the biggest favor by using the lightest weight oil that can properly lubricate your engine. With your warm climate and low mileage I would go as light as possible and then work your way up if you notice any unnecessary knocking @ startup or running. A lot of people with tell you that 0w-30, 5w-30, or 5w-20's are meant for your hybrid but a high quality low weight is going to protect @ startup and full throttle better then there 15w-40 diesel oil from what I have researched. All that while improving gas mileage, not alot but everything helps..

The articles above are not bias towards any certain weight. #2 is more for the heavier weight even, so I am not selling my personal flavor koolaid. I think the test tube viscosity example on page 6 of the pdf speaks for it self..

TbDk

I've used 10w-30 in mine since I bought it almost 4 years ago. Haven't had any problems at all with lubrication. Just make sure what ever weight you go with, to change your oil at regular intervals.

djb383

I believe Dr. Haas is in favor of and proven in his research that lighter/thinner, not heavier, is preferable to better lubrication while maintaining adequate pressure.

One of the most posted Internet oil myths out there is in regard to "flat tappet" cams. If one is running 400+ lbs of valve seat pressure in the valve train of there race engine, a little more ZDDP may be called for........at 55-60 lbs seat pressure in the 4.0L and a most other stock motors, 5W30 should be fine.

In article #2, Dr. Haas says the 1st number is more important than the 2nd number. The good Dr. knows his oil.

SamSissine2

While I think we are on the same team here....., the reason I stated I see the DR. as more pro-heavier oil is he is running 5w-40...

While that is not a 15w-40 as most would reccommend around here it still is a far cry from 0w-30, 0w-20, or 5w-20 that you may read about being used on bobistheoilguy.com. I agree with you & the Dr. on the first # being the most important.

Spoonman

imo 5W is for winter months or colder climates and 10W is for summer months or warmer climates.
In Cali I would personally probably just use the 10W-30 year round.That's my personal opinion.
Synthetic vs. Dino, I have always used dino oil.If I had a brand new vehicle I would probably use a good synthetic but for a used vehicle I always figure stick with what has already been used in it.

djb383

Doesn't 5WXX flow quicker to engine parts 10WXX when the engine is started at below normal operating temp and isn't 5W30 the same vis as 10W30 at normal operating temp????????

djb383

Which chapter is the Dr. addressing using 5W40?

digger90

i used 5w-30 once and there was a lot of tapping noise so on the next oil change i switched to 10w-30 and it quieted down. tapping still there but not as loud. i only use mobile 1 oil with a mobile 1 filter

SamSissine2

"One of the best tools we have to figure out what is behind the hype is the internet. Chevron’s site is one of the easiest to use: Cbest Products, from there I can see the Delo Synthetic 5W-40 I have in my BMW. It is only a group III product (or was when I bought it according to an email reply from their Lubetek center and the msds), but it has shown excellent results in several engines when I’ve analyzed it."

Pg. 16 of 31 (3rd paragraph, on the left of the illustration)

djb383

Help the dummy (me) out....page 16 of 31 of Dr. Haas's papers?

SamSissine2

Correct, once you click my link #2 from above open the pdf. The paper is 31 pages long. Then go to page 16. Hope that helps..

dukie564

^^^ This is correct.

A 5w-30 oil will cause less startup wear on the engine than a 10w-30 oil due to a lower viscosity when cold (about 80% of wear on your engine occurs at startup by the way). At operating temp (212*F +/-), the viscosity is equal to that of a straight 30 oil. This is the reason they stared making multi-viscosity oils in the first place - to reduce engine wear when cold.

Now to me, Chrysler designed the 4.0L to run on SAE 30 oil (10w-30 to be exact per every owners manual and factory service manual). Running anything other than 30 weight as the operating viscosity is going to cause the engine to not perform as it was designed, and is therefore not advisable to use. A higher viscosity oil will only make your engine work harder to pump it, meaning less lubrication. Pressure is not what's most important in lubricating your engine, it's the FLOW of oil that is vital.

However, switching what most people refer to as the "cold weight" to 5w or 0w will not hurt your engine, and in many ways will help it, regardless of the season or climate you are in. "Cold" is relative. In terms of engines, cold is anything below operating temp. So unless you live in a climate that is 200*F year round, you will benefit from using a 5w-30 or even a 0w-30 motor oil. You engine components (eg. starter, oil pump, etc) will also last longer because you are putting less stress on them.


In conclusion, IMO the only oil you should be using is 5w-30. It is the only one that offers factory flow characteristics that the engine components were designed for, while also offering reduced startup wear.

But hey, if you think you're smarter than the people that designed your engine, by all means....

djb383

I thought your original post referred to link #2 as being authored Dr. A. E. Haas, Motor Oil 101 thru 201. Dr. Haas is definitely an advocate of "thinner is better" and gives very detailed evidence as to why.