Higher water temps with CJ-4 spec oil

[DMC3165]

I know how this forum hates just about any question relating to motor oil but I have to ask this question and get feedback from other owners.

For the past year and a half I've been running a CJ-4 spec diesel oil in my car based on the recomendations from vendors and a few others in the Delorean world. I use it mainly because I had been told the additive package in that oil is better suited for cars of our vintage. However right from the start I noticed higher water temps (190-210) and during the summer months the car developed a hot fuel problem that it never had before. In addition it has been taking the cooling fans longer run times to pull the temperature back down to the point where they would normally shut off. I am concerned using this oil is causing more harm then good and the higher temperatures (while not overheating) will lead to premature wear and failures. I have also noticed some mainstream oil manufacturers are now selling zinc boosted oils for older and higher milage cars. I was thinking of going that route in the future. I'll be hauling my car out of storage in a month or so and doing my spring PM getting it ready for the driving season. I was thinking about abandoning the CJ-4 oil in favor of the newer conventional stuff. Any thoughts?

[David T]

According to "conventional wisdom" you only need the high levels of ZDDP early in the engine's life during break-in. Once you wear the cam and followers (or lifters) you don't need as high levels of ZDDP to reduce wear. If you are worried about ZDDP there are oils out there now for higher mileage cars or there are racing and off-road oils. Some use oils for diesels. It isn't that big a deal, especially on old cars that do not accumulate all that much mileage. One benefit of the newer synthetic oils is that they are a lot more slippery and can prevent excessive wear without as much ZDDP. If you changed oils and now the motor is running hotter than is a sign that it is not making things as slippery and the increased friction is causing increased temps. Not good. I would remove that oil and try something else. It could also be possible you have a problem with your cooling system and it is just a coincidence that it happened when you changed oils. If changing oil does not lower the temps you will have to look elsewhere for your cooling problem.
David Teitelbaum

[Rich W]

According to "conventional wisdom" you only need the high levels of ZDDP early in the engine's life during break-in. Once you wear the cam and followers (or lifters) you don't need as high levels of ZDDP to reduce wear. If you are worried about ZDDP there are oils out there now for higher mileage cars or there are racing and off-road oils. Some use oils for diesels. It isn't that big a deal, especially on old cars that do not accumulate all that much mileage. One benefit of the newer synthetic oils is that they are a lot more slippery and can prevent excessive wear without as much ZDDP. If you changed oils and now the motor is running hotter than is a sign that it is not making things as slippery and the increased friction is causing increased temps. Not good. I would remove that oil and try something else. It could also be possible you have a problem with your cooling system and it is just a coincidence that it happened when you changed oils. If changing oil does not lower the temps you will have to look elsewhere for your cooling problem.
David Teitelbaum

+1 with David's comments...it may just be a timing coincidence that the cooling system appears different after you changed oil types.

FWIW, I use Castrol GTX Conventional 20W-50 on all my PRV powered DeLoreans and Castrol GTX High Mileage in almost all the rest of my cars.

I use Shell Rotella T diesel formula oil in the 7.3L Diesel RV, as well as in my Ford gas powered V8 trucks...and in the Chevy 350 V8 in the D Rex.

Later,
Rich W.

[DMC3165]

At the risk of having the thread locked I use to run a conventional 10w-30 in the colder months and a 10w40 in the summer. The CJ-4 is a 15w-40. I noticed right away higher oil press on the gauge but also higher water temps but only slightly. One of the other reasons I ask is I had an LT1 years back that I ran a 5w-50 synthetic in and when I switched to a lighter 5w-30 the motor ran much cooler and suffered no ill effects from the lighter oil. I know PRV's call for heavier oils but I'm thinking I might just switch back to the other stuff.

I'm glad you responded to this David because I read your thread about the warped head in your car. and in it you stated it looked as if it was overheated but yet you never overheated the motor. This is where my concern is in running heavier oils. Many owners I've spoken to routinely tell me they run water temps at 220 and that seems a bit too high for me especially over long periods of time. My engines holding up well with 60K on it and I'd like to keep it that way for as long as possible. Do either of you guys feel it would be detrimental to going back to a 10-40?

[David T]

You should have no problems "going back". As for my overheat, I doubt it has anything to do with oil. On the subject of engine operating temperature, the motor is designed to run at that temperature. You should be able to go up to 240 without any ill effects. 50/50 water and anti-freeze under 15 psi won't boil till 256 f. I am going to review all of the history on my car and see if there is any indication of even a minor problem with the cooling system so I can figure out if and when the motor overheated. The possibility will exist that it happened before I bought the car and it didn't become a problem till recently.
David Teitelbaum

[Ron]

You should have no problems "going back". As for my overheat, I doubt it has anything to do with oil. ...
+1

[ccurzio]

You should have no problems "going back".

Back where?

http://i.imgur.com/ba6PTzm.jpg

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