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Switch to Synthetic or run conventional with an additive?

M

MudfrogK5

NAXJA Forum User
Location
Roanoke VA
90 w/ 4.0. Mileage at 179k. Which would be more beneficial? When I do my oil pump tonight I'll obviously be doing an oil change. So should I stick with the conventional oil that has been ran since day one and maybe add an additive, run it without additive or switch to synthetic? Anyone have any insight on high mileage oils?
 
In reality, oil is oil. Just like gasoline is gasoline. If your oil meets the industry specs for its grade, use it. There may be some slight differences in oil additives (detergent, etc) and the lowest priced oils are probably the lowest quality product. Since the 4.0L is not a Hi-Perf engine and you live in a warmer climate, their is no real benefit to using synthetic oil. You greatest benefit is achieved by performing regular oil changes and using good quality oil filters
 
Tim_MN said:
In reality, oil is oil. Just like gasoline is gasoline. If your oil meets the industry specs for its grade, use it. There may be some slight differences in oil additives (detergent, etc) and the lowest priced oils are probably the lowest quality product. Since the 4.0L is not a Hi-Perf engine and you live in a warmer climate, their is no real benefit to using synthetic oil. You greatest benefit is achieved by performing regular oil changes and using good quality oil filters
Click to expand...


Truth.
 
Since you are going to change out your pump I assume you found that you did indeed have low oil pressure when you checked it with the mechanical gauge. Just curious what the numbers were which might help the next person with a similar symptom.

You said that you had read that the pumps on the 4.0 were notorious for failing at around 150k miles but I just never got that sense from following the forum. Oh well, sounds like a fun project.

Re: high mileage oils, I used Valvoline in my '85 and more recently '93 until switching to Rotella for the (presumed) ZDDP benefit. For the '93 I found that the high mileage oil did seal up the very slight seepage from here and there about the motor, barely enough for the occasional drip. If you don't have a leak, I don't see a lot of benefit to the high mileage oils.
 
I didn't personally test it. One of my customers volunteered to and said it was indeed low. I'll ask if they remember what the exact pressure was. It has started acting like the oil pump as well, occasionally at idle the light will be off but when driving the light will come on and increase in brightness as the rpm's go up.

I do have a leak but I believe it is at the valve cover gasket which I will be replacing as well. If there are any others I'm not really sure yet but should know by the weekend.
 
Last edited:
Pelican said:
Since you are going to change out your pump I assume you found that you did indeed have low oil pressure when you checked it with the mechanical gauge. Just curious what the numbers were which might help the next person with a similar symptom.

You said that you had read that the pumps on the 4.0 were notorious for failing at around 150k miles but I just never got that sense from following the forum. Oh well, sounds like a fun project.

Re: high mileage oils, I used Valvoline in my '85 and more recently '93 until switching to Rotella for the (presumed) ZDDP benefit. For the '93 I found that the high mileage oil did seal up the very slight seepage from here and there about the motor, barely enough for the occasional drip. If you don't have a leak, I don't see a lot of benefit to the high mileage oils.
Click to expand...
Valvoline does have ZDDP in it. Rotella may have more? I dont know.

With the properties of most synthetics (including detergents), it can be and is beneficial to use. Amsoil, Valvoline Syn power (and the blend), Pennzoil Platinum have a good amount of ZDDP in them as well. Synthetic oil can help extend the life of your engine (Other components as well). And you can also see an increase in mileage.
I run full syn in my engine, along with some MMO. I run Amsoil Universal ATF in my trans and t-case. And full syn in my diffs. And my XJ runs better than it did before the switch.
 
Running conventional or synthetic is personal choice. There is no right or wrong answer. This topic has been gone round the horn many times here. SEARCH and you'll find lots of light reading.

Want more or want to really dig in? Go to "bobistheoilguy.com".
 
birchlakeXJ said:
Running conventional or synthetic is personal choice. There is no right or wrong answer. This topic has been gone round the horn many times here. SEARCH and you'll find lots of light reading.

Want more or want to really dig in? Go to "bobistheoilguy.com".
Click to expand...

x2 with BirchlakeXJ.

You should run what is best for you.

I run Shell Rotella 10w30 Dino--cheap at Walmart; it has ZDDP (maybe not needed in a low-compression flat-tappet engine, but I like having it in there); I don't need synthetic for heat, extended change intervals, or extreme pressures--those are where synthetics excel; and any diesel oil will clean the heck out of your engine's guts, which I prefer to sludge.

My .02 worth.
 
I picked up some cheap Quaker State 10w30 this afternoon at Walmart.. $11 for 5 quarts can't really been beat.

I'm going to try using a better filter before I change my oil pump. I used a really cheap Champ filter, I read that paper filters can collapse and cause really bad oil pressure. Is there any truth to this?
 
I've been converting cars to synthetic since 1982. Never a problem (usually beneficial in several regards).

You'd be best by using an AUTO-Rx program for high mileage cars. See their site, and the thousands upon thousands of posts on www.bobistheoilguy.com. I do a MOLASOAK on mine, first. Avoid EVER using SEAFOAM.

Then, run the oil of your choice. I use REDLINE, with LC-20, and used oil analysis -- by an expert -- confirms the choice.

Use a low-restriction, high capacity oil filter by BALDWIN or DONALDSON. I get mine through marine or truck supply houses.

Keeping a clean air filter is more important than anything you can do vis-a-vis oil type & filter for longest engine life.
 
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