Thank you for clarification! On most vehicles 13 would scare the crap outta me!! Nice to know my engines like new :-):-)

On Lucas.... good stuff! I have run it in all my cars for years! Has worked well in my 66 mustang gt with the original a-code 289... helps with oil control.

 

Kinda on topic.. has anyone noticed a substantial difference in oil pressure between 5w30 and 10w30, I know the 10w30 is thicker so it will give better oil pressure but I went from 40-50 psi (5w30) to the gauge being completely pegged over 80 (still about .5 a quart low too using 10w30). Is that a normal difference?

 

You'll wanna read this - http://www.bobistheoilguy.com/
Go through motor oil university. You will see that 5w-30 and 10w-30 have the same viscosity at operating temp, but the 10w-30 many of us run has poorer lubrication qualities at start-up temp.

I don't want to hi-jack this thread so I won't mention my oil preference.

 

Yea I have a different issue going on, it's now reading 0 psi but still has plenty of oil. I'm assuming the sending unit is going bad.

 

[QUOTE=Moncheche;1082023]You'll wanna read this - http://www.bobistheoilguy.com/
Go through motor oil university. You will see that 5w-30 and 10w-30 have the same viscosity at operating temp, but the 10w-30 many of us run has poorer lubrication qualities at start-up temp.

Interesting link Read.
As a hot climate, year round loyal straight 30w guy, change doesn't come easy. But I will try a lighter multi weight on the next change to see if I can see or hear a difference. ??

 

The pressure / viscosity is directly related to main bearing clearances. On OLDER high mileage engines use a heavier base oil IE: 20 W40 ,30 wt, 40 wt. to increase idle oil pressure to a minimum of 15PSI. When 40wt will not do the trick it is time to rebuild the engine.

 

Oil pressure for a 4.0 is 10 psi per 1000 rpm, for my 2000 xj at idle it only calls for 13 to 16 psi, thats it .And most motors only require the famous 10 psi per 1000 rpm which has been the norm for about 60 years at least. Anyways it is right in the F.S.M or your CHILTONS or SIMILAR you guys do have a book on your JEEPS Right lol.

 

Todays 40wt oils will have the same viscosity at operating temps as 0/10/20/30wts. The key word there is operating temp. It will be thicker at start-up, and technically would provide more 'pressure' because it's harder for the pump to flow, but the lubrication of your engine would be poorer. Took me awhile to wrap my head around that. Give that bobistheoilguy.com a good read through. It changed my mind on a few myths about oil that had been passed down to me over the years.

The viscosity on start-up is just poorer. I didn't believe it until I saw data provided by someone not associated with an oil company.

 

Way it was explained to me is the viscosity you want is directly related to the.size of your oiling passages. For example my 1966 289 v8 has much larger passages the my 4.0 so I can get away with thicker oil. With smaller passages it is just as stated above. Pump works harder with worse lubrication because the passages aren't big enough for that thick oil to flow properly.