Prefered synthetic oil for 4.0?

I have ran regular oil and synthetic back on several vehicles and done several combinations. When cleaning out slush on a recently purchased used one, I would often perform engine flushes and run regular oil after and a filter changed, then switch to synthetic and new filter without issues. That's air-cooled and water-cooled. If the seals are good, it doesn't matter that you throw at it. As said before, unless specific to a motor build, buy you know and feel comfortable with.

Playing with synthetics and engine oil change intervals can be fun, and expensive as well.
 
My TJ gets Royal Purple due the Zink and using it mainly for plowing in cold weather.
My Vette also gets Royal Purple for the Zink.
My Duramax gets Rotella R6. Everything gets changed at 6K miles.
All my 2cycles get Klotz.
 
  • Like
Reactions: Phil Younger
I've got 2 jugs of Valvoline "Full Synthetic with maxlife technology" ready for my next change, because I read it had one of the best anti-wear film strengths of any commonly available oil, and it happens to cost exactly the same as the Castrol GTX High Mileage synth blend that I was using before. If my lifter tap noise gets louder, I'll go back to the Castrol. I have zero care for whether it's conventional or synthetic, but most the high mileage oils are at least a blend.

I have a slight seep in the back of the motor that to be honest isn't even bad enough for me to have checked whether it's actually a RMS or a valve cover. I've only used High mileage oils in it since purchase, in an effort to keep that leak slow.
 
freedom_in_4low said:
I've got 2 jugs of Valvoline "Full Synthetic with maxlife technology" ready for my next change, because I read it had one of the best anti-wear film strengths of any commonly available oil, and it happens to cost exactly the same as the Castrol GTX High Mileage synth blend that I was using before. If my lifter tap noise gets louder, I'll go back to the Castrol. I have zero care for whether it's conventional or synthetic, but most the high mileage oils are at least a blend.

I have a slight seep in the back of the motor that to be honest isn't even bad enough for me to have checked whether it's actually a RMS or a valve cover. I've only used High mileage oils in it since purchase, in an effort to keep that leak slow.
Click to expand...
Be interesting to see if your seep changes.
 
WDE said:
The one time I used a synthetic, I developed a RMS leak. I changed back to Valvoline conventional and have had no RMS leak since. Anecdotal but true in my case. Coincidental? I don't care enough to try again.
Click to expand...
Same here. Switched to Mobile 1, boom, RMS leak within 50 miles. Dropped it out and went back to Dino, no more leaks.
 
Apparition said:
Be interesting to see if your seep changes.
Click to expand...
I ran some netherlands cheap semi synthetic oil before, the engine on coldstart would shake whole car, and it would make tsak tsak sound passing 2000 rpms, once i switched to valvoline synth the coldstart shake and other odd sounds disappeared. But almost all oils here are counterfeited, though i buy valvoline from certified shop. Guess electric car or truck engine diesel is the only solution. I heard counterfeiting semitruck oils is rare and most are original authentic.
 
Turdworlder said:
I ran some netherlands cheap semi synthetic oil before, the engine on coldstart would shake whole car, and it would make tsak tsak sound passing 2000 rpms...
Click to expand...
Those symptoms sound fuel or spark related.

If you want to use diesel engine oil in a gasoline engine, the oil should be the same viscosity as manufacturer recommended, plus have both the API CK-4 and API SN specifications. If the diesel engine oil is not in the "S" category, it is most likely not safe for an unmodified automotive gasoline engine. It is best to compare data sheets. A diesel engine oil with very high Zinc content will kill a gasoline engine's catalytic converter.

BTW, I love Kazak rug designs.
 
  • Like
Reactions: Phil Younger
Went to conventional 10W-30 oil 3 days ago with the oil change with the TJ for the first time after using at least semi-synthetics for 20 years in this and other vehicles. Mileage hasn't changed at all (still great at around 21mpg when driven in a civilised manner), performance feels great/responsive, engine temp, oil pressure is the same, no ticking (which I got when I tried a full synthetic), etc.

I'll give it more time but I have a feeling I wasted $ on this Jeep with semi-synthetic over the last few years and should've just went conventional oil to start off with...
 
Just rebuilt a 2005 4.0 I acquired with a 6 speed manual, with about 140,000 miles on it. When I tore it down I found the lifters and cam worn and the piston skirts scuffed. When I received the new Melling cam and lifters there was a note in the box concerning a lack of ZDDP (Zinc dialkyldithiophosphate) in modern oils. This is a necessity for flat tappet cams, which have disappeared in the modern word. If your like me and love our dinosaur flat tappet engines look for oils that contain this stuff, most diesel oil does have a lot of this and oddly Mobil 1 for european engines does also. Do some research and get oil with ZDDP in it. I even started using 15-40 oil in my boat that runs a flat tappet cam in a 350 Chevy.
 
  • Like
Reactions: Phil Younger
Yendra Built said:
Just rebuilt a 2005 4.0 I acquired with a 6 speed manual, with about 140,000 miles on it. When I tore it down I found the lifters and cam worn and the piston skirts scuffed. When I received the new Melling cam and lifters there was a note in the box concerning a lack of ZDDP (Zinc dialkyldithiophosphate) in modern oils. This is a necessity for flat tappet cams, which have disappeared in the modern word. If your like me and love our dinosaur flat tappet engines look for oils that contain this stuff, most diesel oil does have a lot of this and oddly Mobil 1 for european engines does also. Do some research and get oil with ZDDP in it. I even started using 15-40 oil in my boat that runs a flat tappet cam in a 350 Chevy.
Click to expand...
What few ZDDP enthusiasts understand is the additional zinc is only really needed if you're using a high-lift cam and stiff valve springs. Modern oils contain zinc and there's enough of it for our stone-age 4.0 and a stock non-high lift cam. That's why our TJ engines last well into the high 200k mile ranges without any cam or lifter problems. Now if I had a hot rod '57 Chevy with a big block and high-lift cam with appropriate stiffer springs absolutely I'd be running more zinc. In my TJ with its stock engine? Nope.
 
WDE said:
The one time I used a synthetic, I developed a RMS leak. I changed back to Valvoline conventional and have had no RMS leak since. Anecdotal but true in my case. Coincidental? I don't care enough to try again.
Click to expand...

Same here, was it Castrol? Did you get a free need for speed hat like me? I switched back to Pennzoil synthetic and leak is de minimis at this time. I even bought all the parts to replace the RMS, including the oil pan gasket, but Pennzoil synthetic high mileage saved the day.
 
Just sayin, I tore down a 4.0 with 140,000 miles and the the top of the lobes were worn down and showed spalling, and the lifters were spalled and dished in instead of the slightly radiused out like new ones. Too much idle time after start up in cold weather could possibly cause this also.
 
freedom_in_4low said:
I've got 2 jugs of Valvoline "Full Synthetic with maxlife technology" ready for my next change, because I read it had one of the best anti-wear film strengths of any commonly available oil, and it happens to cost exactly the same as the Castrol GTX High Mileage synth blend that I was using before. If my lifter tap noise gets louder, I'll go back to the Castrol. I have zero care for whether it's conventional or synthetic, but most the high mileage oils are at least a blend.

I have a slight seep in the back of the motor that to be honest isn't even bad enough for me to have checked whether it's actually a RMS or a valve cover. I've only used High mileage oils in it since purchase, in an effort to keep that leak slow.
Click to expand...

If you still have the leak, try the Pennzoil synthetic high mileage.
Yendra Built said:
Just sayin, I tore down a 4.0 with 140,000 miles and the the top of the lobes were worn down and showed spalling, and the lifters were spalled and dished in instead of the slightly radiused out like new ones. Too much idle time after start up in cold weather could possibly cause this also.
Click to expand...

How dare you have an opinion against the forum leaders! :eek:
 
My TJ (196k) dripped a few drops a week on mobil1. Switched to a regular (non-high mile) conventional oil and the drips completely stopped after about 200 miles. It was amazing and I still check often because I can't believe it actually worked. The RMS still gets a little wet, but not a single drop in my garage now.
 
Before I rebuilt my motor, I always ran 10w-30 Valvoline High mileage Full synthetic. Now that I just rebuilt it, im now only using 10w-30 valvoline conventional.
 
  • Like
Reactions: Jerry Bransford
Top Bottom
Back