I'm using 10w-40 to increase my low oil pressure, which is caused by bad bearings. It increased the pressure from 5 psi to 9 psi over 5w-30 when I changed the oil this summer. But now it's winter here in Minnesota -- which weight should I use?
It seems to me that it's a matter of the least worst -- when the engine is warmed up after about 20 minutes, the 5w-30 will cause the pressure to go back down to 5 psi, which is bad. But when I start it in the cold, the 10w-40 is too thick to reach the top right away, which is bad.
Either way, the oil won't reach the top at some point. And important note -- the pressure is only low at idle and is fine at cruising speed, and increases to normal from low pressure when I accelerate.
I wouldn't even use 10W40 in he summer and follow the spec to use 10W30 year round in all our Jeeps. Always have and always will. And yeah, my oil pressure is just a little low at idle on my 96 4.0 but don't believe it's doing any damage and picks right up when accelerating.
For MN winters believe I'd be using a block/engine heater plugged in overnight if possible.
I started using 5w40 Rotella T6 synthetic just to see if it was any good. It got rid of some noises, seems like good stuff. Oil pressure is pretty stable except at warm-up where it can get somewhat low idling after a stop.
[CENTER][URL="http://www.jeepforum.com/forum/f197/breckenridge-redemption-build-thread-3111777/#post29271881"]Build Thread: "The Jeep" 1995 ZJ Laredo I6 212k. 20 years 1 family.[/URL]
The New DD: 2015 Dodge Charger SXT Rallye[/CENTER]