djb383

Could we presume we're not talking about rediculously long extended oil change intervals and racing?

Radi

nm

Big blue99

I used 10w 30 in my first oil change since I bought my 99 in January. Added a quart of lucas stabilizer.....had been running 40 lbs consistently, now running 50...... just my info...

Radi

Out of curiosity...why? Is there a problem you are trying to address?

bigbadon

Why,why,why are so many people trying to increase oil pressure?
As an engineer, the oil pump is positive displacement, which means it is going to pump the same volume of oil regardless of pressure. Low pressure is an indication of engine wear and no amount of oil pressure can compensate for that,nor does it need to.
http://lubricants.s5.com/oil_pressure.htm

s346k

this is funny. I urge you to scour your local car meets, find the guys making power. not one of them is using a 0 grade motor oil, regardless of which brand na boost n2o whatever. in fact, just send Nelson racing engines an email asking if they'd recommend you use 0w40 in your 2200 hp twin turbo big block.

el oh el

and op. check it with a mechanical gauge first. get a known value of pressure before jumping to conclusions.

djb383

Here's an interesting read.......0W5! I find that there r lots of Ronnie Racer types at local car meets.

http://www.popularmechanics.com/cars...tually-stock-2

Radi

Car meets? Guess what NHRA pro-stock, some NASCAR and many others who do it for a living run?

salad

Eventually... in theory... but this is irrelevant. We are not talking about 200°C oil temperatures, nor are we talking about 20K OCIs.

Anyway word has it that Amsoil 10W30 does not contain VIIs.

Can't. Stuck in "I Have To Be Right" mode!

md21722

The bottom line is that for most folks, just put what the manufacturer recommends and forget about.

I believe the "40 weight craze" of the Jeep 4.0 started around 10 years ago when folks noticed Mobil 1 10w-30 was causing high iron but switching to Delvac 5w-40 cut the iron wear down. At the time, Castrol was about the only competitor and many did not like the fact that Castrol used hydrocracked base stocks compared to Mobil's PAO/Ester base stocks. Today with other alternatives available, folks have noticed that other synthetic 10w-30 oils do not cause elevated iron wear so it was unlikely a viscosity issue but rather something specific to Mobil 1.

Taking a 3,000 mile oil change into consideration, engine oil is likely to shear between 1,000 and 2,000 miles before it thickens back up to its original grade. The fuel economy tests are performed starting around 1,000 miles. Some people may notice an increase in the rate of oil consumption/leakage between 1,000 and 2,000 miles. In other words, the oil does not stay the same viscosity for the entire oil change interval even if you're running normal (rather than extended) oil change intervals.

md21722

One oil does not constitute "many".

djb383

Really?..........I did not know that, but have never seen any data to support 1K-2K mile shear either.

djb383

.....and if I understand Motor Oil 103 correctly, most synthetics don't have VIIs, or very little.

s346k

youre also using an engine for comparison that gets rebuilt after a 500 mile race and or 5 miles worth of passes.

I know plenty of "Ronny racers" with 1k+ hp cars that get driven thousands of miles a year on the street and track both. the thin oil race teams use is for power. the bearings are coated etc etc etc and can't be compared to an engine seeing any amount of time on the street.

keep reading magazines about engines you'll never see, touch, or work on. in the mean time I'll maintain contact with the real world.

md21722

Conventional oils require more viscosity improvers than synthetics of the same viscosity.

When cold weather pumpability is a concern, synthetic 10w-30 is going to perform better than conventional 5w-30. The conventional 5w-30 may also shear down 20% compared to a synthetic which not going to shear down much at all.